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  • UITableView : crash when adding a section footer view in empty section

    - by Supernico
    Hi everyone, This is the first time I ask a question here, but I have to say this site has been a tremendous help for me over the last couple months (iphone-dev-wise), and I thank you for that. However, I didn't find any solution for this problem I'm having: I have a UITableView with 2 sections, and no rows when the app is launched for the first time. The user can fill the sections later on as he wishes (the content is not relevant here). The UITableView looks good when filled with rows, but looks pretty ugly when there is none (the 2 header sections are stuck together with no white space in between). That is why I'd like to add a nice "No row" view in between when there is no row. I used viewForFooterInSection: - (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section { if(section == 0) { if([firstSectionArray count] == 0) return 44; else return 0; } return 0; } - (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section{ if(section == 0) { UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(200, 10, 50, 44)]; label.backgroundColor = [UIColor clearColor]; label.textColor = [UIColor colorWithWhite:0.6 alpha:1.0]; label.textAlignment = UITextAlignmentCenter; label.lineBreakMode = UILineBreakModeWordWrap; label.numberOfLines = 0; label.text = @"No row"; return [label autorelease]; } return nil; } - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 2; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { if(section == 0) { return [firstSectionArray count]; } return [secondSectionArray count]; } This works great : the footer view appears only when there is no row in section 0. But my app crashes when I enter edit mode and delete the last row in section 0: Assertion failure in -[UIViewAnimation initWithView:indexPath:endRect:endAlpha:startFraction:endFraction:curve:animateFromCurrentPosition:shouldDeleteAfterAnimation:editing:] Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Cell animation stop fraction must be greater than start fraction' This does not happen when there are several rows in section 0. It only happens when there is only one row left. Here's the code for edit mode: - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { // If row is deleted, remove it from the list. if (editingStyle == UITableViewCellEditingStyleDelete) { // Find the book at the deleted row, and remove from application delegate's array. if(indexPath.section == 0) { [firstSectionArray removeObjectAtIndex:indexPath.row]; } else { [secondSectionArray removeObjectAtIndex:indexPath.row]; } // Animate the deletion from the table. [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationBottom]; [tableView reloadData]; } } Does anyone have any idea why this is happening? Thanks

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  • Maze Navigation in Player Stage with Roomba

    - by Scott
    Here is my code: /* Scott Landau Robot Lab Assignment 1 */ // Standard Java Libs import java.io.*; // Player/Stage Libs import javaclient2.*; import javaclient2.structures.*; import javaclient2.structures.sonar.*; // Begin public class SpinningRobot { public static Position2DInterface pos = null; public static LaserInterface laser = null; public static void main(String[] args) { PlayerClient robot = new PlayerClient("localhost", 6665); laser = robot.requestInterfaceLaser(0, PlayerConstants.PLAYER_OPEN_MODE); pos = robot.requestInterfacePosition2D(0,PlayerConstants.PLAYER_OPEN_MODE); robot.runThreaded (-1, -1); pos.setSpeed(0.5f, -0.25f); // end pos float x, y; x = 46.0f; y = -46.0f; boolean done = false; while( !done ){ if(laser.isDataReady()) { float[] laser_data = laser.getData().getRanges(); System.out.println("== IR Sensor =="); System.out.println("Left Wall Distance: "+laser_data[360]); System.out.println("Right Wall Distance: " +laser_data[0]); // if laser doesn't reach left wall, move to detect it // so we can guide using left wall if ( laser_data[360] < 0.6f ) { while ( laser_data[360] < 0.6f ) { pos.setSpeed(0.5f, -0.5f); } } else if ( laser_data[0] < 0.6f ) { while(laser_data[0<0.6f) { pos.setSpeed(0.5f, 0.5f); } } pos.setSpeed(0.5f, -0.25f); // end pos? done = ( (pos.getX() == x) && (pos.getY() == y) ); } } } } // End I was trying to have the Roomba go continuously at a slight right curve, quickly turning away from each wall it came to close to if it recognized it with it's laser. I can only use laser_data[360] and laser_data[0] for this one robot. I think this would eventually navigate the maze. However, I am using the Player Stage platform, and Stage freezes when the Roomba comes close to a wall using this code, I have no idea why. Also, if you can think of a better maze navigation algorithm, please let me know. Thank you!

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  • Advice on displaying and allowing editing of data using ASP.NET MVC?

    - by Remnant
    I am embarking upon my first ASP.NET MVC project and I would like to get some input on possible ways to display database data and general best practice. In short, the body of my webpage will show data from my database in a table like format, with each table row showing similar data. For example: Name Age Position Date Joined Jon Smith 23 Striker 18th Mar 2005 John Doe 38 Defender 3rd Jan 1988 In terms of functionality, primarily I’d like to give the user the ability to edit the data and, after the edit, commit the edit to the database and refresh the view.The reason I want to refresh the view is because the data is date ordered and I will need to re-sort if the user edits a date field. My main question is what architecture / tools would be best suited to this fulfil my requirements at a high level? From the research I have done so far my initial conclusions were: ADO.NET for data retrieval. This is something I have used before and feel comfortable with. I like the look of LINQ to SQL but don’t want to make the learning curve any steeper for my first outing into MVC land just yet. Partial Views to create a template and then iterate through a datatable that I have pulled back from my database model. jQuery to allow the user to edit data in the table, error check edited data entries etc. Also, my intial view was that caching the data would not be a key requirement here. The only field a user will be able to update is the field and, if they do, I will need to commit that data to the database immediately and then refresh the view (as the data is date sorted). Any thoughts on this? Alternatively, I have seen some jQuery plug-ins that emulate a datagrid and provide associated functionality. My first thoughts are that I do not need all the functionality that comes with these plug-ins (e.g. zebra striping, ability to sort by column using sort glyph in column headers etc .) and I don’t really see any benefit to this over and above the solution I have outlined above. Again, is there reason to reconsider this view? Finally, when a user edits a date , I will need to refresh the view. In order to do this I had been reading about Html.RenderAction and this seemed like it may be a better option than using Partial Views as I can incorporate application logic into the action method. Am I right to consider Html.RenderAction or have I misunderstood its usage? Hope this post is clear and not too long. I did consider separate posts for each topic (e.g. Partial View vs. Html.RenderAction, when to use jQury datagrid plug-in) but it feels like these issues are so intertwined that they need to be dealt with in contect of each other. Thanks

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  • Miller-rabin exception number?

    - by nightcracker
    Hey everyone. This question is about the number 169716931325235658326303. According to http://www.alpertron.com.ar/ECM.HTM it is prime. According to my miller-rabin implementation in python with 7 repetitions is is composite. With 50 repetitions it is still composite. With 5000 repetitions it is STILL composite. I thought, this might be a problem of my implementation. So I tried GNU MP bignum library, which has a miller-rabin primality test built-in. I tested with 1000000 repetitions. Still composite. This is my implementation of the miller-rabin primality test: def isprime(n, precision=7): if n == 1 or n % 2 == 0: return False elif n < 1: raise ValueError("Out of bounds, first argument must be > 0") d = n - 1 s = 0 while d % 2 == 0: d //= 2 s += 1 for repeat in range(precision): a = random.randrange(2, n - 2) x = pow(a, d, n) if x == 1 or x == n - 1: continue for r in range(s - 1): x = pow(x, 2, n) if x == 1: return False if x == n - 1: break else: return False return True And the code for the GMP test: #include <gmp.h> #include <stdio.h> int main(int argc, char* argv[]) { mpz_t test; mpz_init_set_str(test, "169716931325235658326303", 10); printf("%d\n", mpz_probab_prime_p(test, 1000000)); mpz_clear(test); return 0; } As far as I know there are no "exceptions" (which return false positives for any amount of repetitions) to the miller-rabin primality test. Have I stumpled upon one? Is my computer broken? Is the Elliptic Curve Method wrong? What is happening here? EDIT I found the issue, which is http://www.alpertron.com.ar/ECM.HTM. I trusted this applet, I'll contact the author his applet's implementation of the ECM is faulty for this number. Thanks. EDIT2 Hah, the shame! In the end it was something that went wrong with copy/pasting on my side. NOR the applet NOR the miller-rabin algorithm NOR my implementation NOR gmp's implementation of it is wrong, the only thing that's wrong is me. I'm sorry.

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  • Non-linear regression models in PostgreSQL using R

    - by Dave Jarvis
    Background I have climate data (temperature, precipitation, snow depth) for all of Canada between 1900 and 2009. I have written a basic website and the simplest page allows users to choose category and city. They then get back a very simple report (without the parameters and calculations section): The primary purpose of the web application is to provide a simple user interface so that the general public can explore the data in meaningful ways. (A list of numbers is not meaningful to the general public, nor is a website that provides too many inputs.) The secondary purpose of the application is to provide climatologists and other scientists with deeper ways to view the data. (Using too many inputs, of course.) Tool Set The database is PostgreSQL with R (mostly) installed. The reports are written using iReport and generated using JasperReports. Poor Model Choice Currently, a linear regression model is applied against annual averages of daily data. The linear regression model is calculated within a PostgreSQL function as follows: SELECT regr_slope( amount, year_taken ), regr_intercept( amount, year_taken ), corr( amount, year_taken ) FROM temp_regression INTO STRICT slope, intercept, correlation; The results are returned to JasperReports using: SELECT year_taken, amount, year_taken * slope + intercept, slope, intercept, correlation, total_measurements INTO result; JasperReports calls into PostgreSQL using the following parameterized analysis function: SELECT year_taken, amount, measurements, regression_line, slope, intercept, correlation, total_measurements, execute_time FROM climate.analysis( $P{CityId}, $P{Elevation1}, $P{Elevation2}, $P{Radius}, $P{CategoryId}, $P{Year1}, $P{Year2} ) ORDER BY year_taken This is not an optimal solution because it gives the false impression that the climate is changing at a slow, but steady rate. Questions Using functions that take two parameters (e.g., year [X] and amount [Y]), such as PostgreSQL's regr_slope: What is a better regression model to apply? What CPAN-R packages provide such models? (Installable, ideally, using apt-get.) How can the R functions be called within a PostgreSQL function? If no such functions exist: What parameters should I try to obtain for functions that will produce the desired fit? How would you recommend showing the best fit curve? Keep in mind that this is a web app for use by the general public. If the only way to analyse the data is from an R shell, then the purpose has been defeated. (I know this is not the case for most R functions I have looked at so far.) Thank you!

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  • Evaluation of CTEs in SQL Server 2005

    - by Jammer
    I have a question about how MS SQL evaluates functions inside CTEs. A couple of searches didn't turn up any results related to this issue, but I apologize if this is common knowledge and I'm just behind the curve. It wouldn't be the first time :-) This query is a simplified (and obviously less dynamic) version of what I'm actually doing, but it does exhibit the problem I'm experiencing. It looks like this: CREATE TABLE #EmployeePool(EmployeeID int, EmployeeRank int); INSERT INTO #EmployeePool(EmployeeID, EmployeeRank) SELECT 42, 1 UNION ALL SELECT 43, 2; DECLARE @NumEmployees int; SELECT @NumEmployees = COUNT(*) FROM #EmployeePool; WITH RandomizedCustomers AS ( SELECT CAST(c.Criteria AS int) AS CustomerID, dbo.fnUtil_Random(@NumEmployees) AS RandomRank FROM dbo.fnUtil_ParseCriteria(@CustomerIDs, 'int') c) SELECT rc.CustomerID, ep.EmployeeID FROM RandomizedCustomers rc JOIN #EmployeePool ep ON ep.EmployeeRank = rc.RandomRank; DROP TABLE #EmployeePool; The following can be assumed about all executions of the above: The result of dbo.fnUtil_Random() is always an int value greater than zero and less than or equal to the argument passed in. Since it's being called above with @NumEmployees which has the value 2, this function always evaluates to 1 or 2. The result of dbo.fnUtil_ParseCriteria(@CustomerIDs, 'int') produces a one-column, one-row table that contains a sql_variant with a base type of 'int' that has the value 219935. Given the above assumptions, it makes sense (to me, anyway) that the result of the expression above should always produce a two-column table containing one record - CustomerID and an EmployeeID. The CustomerID should always be the int value 219935, and the EmployeeID should be either 42 or 43. However, this is not always the case. Sometimes I get the expected single record. Other times I get two records (one for each EmployeeID), and still others I get no records. However, if I replace the RandomizedCustomers CTE with a true temp table, the problem vanishes completely. Every time I think I have an explanation for this behavior, it turns out to not make sense or be impossible, so I literally cannot explain why this would happen. Since the problem does not happen when I replace the CTE with a temp table, I can only assume it has something to do with the functions inside CTEs are evaluated during joins to that CTE. Do any of you have any theories?

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  • Creating a variable list Pashua, OS X & Bash.

    - by S1syphus
    First of all, for those that don't know pashua is a tool for creating native Aqua dialog windows. An example of what a window config looks like is # pashua_run() # Define what the dialog should be like # Take a look at Pashua's Readme file for more info on the syntax conf=" # Set transparency: 0 is transparent, 1 is opaque *.transparency=0.95 # Set window title *.title = Introducing Pashua # Introductory text tb.type = text tb.default = "HELLO WORLD" tb.height = 276 tb.width = 310 tb.x = 340 tb.y = 44 if [ -e "$icon" ] then # Display Pashua's icon conf="$conf img.type = image img.x = 530 img.y = 255 img.path = $icon" fi if [ -e "$bgimg" ] then # Display background image conf="$conf bg.type = image bg.x = 30 bg.y = 2 bg.path = $bgimg" fi pashua_run "$conf" echo " tb = $tb" The problem is, Pashua can't really get output from stdout, but it can get arguments. Following on from what Dennis Williamson posted here. What ideally it should do is generate an output file based on information from a text file, To executed in pashua_run ore add the pashua_run around the window argument: count=1 while read -r i do echo "AB${count}.type = openbrowser" echo "AB${count}.label = Choose a master playlist file" echo "AB${count}.width=310" echo "AB${count}.tooltip = Blabla filesystem browser" echo "some text with a line from the file: $i" (( count++ )) done < TEST.txt >> long.txt SO the output is AB1.type = openbrowser AB1.label = Choose a master playlist file AB1.width=310 AB1.tooltip = Blabla filesystem browser some text with a line from the file: foo AB2.type = openbrowser AB2.label = Choose a master playlist file AB2.width=310 AB2.tooltip = Blabla filesystem browser some text with a line from the file: bar AB3.type = openbrowser AB3.label = Choose a master playlist file AB3.width=310 AB3.tooltip = Blabla filesystem browser some text with a line from the file: dev AB4.type = openbrowser AB4.label = Choose a master playlist file AB4.width=310 AB4.tooltip = Blabla filesystem random So if there is a clever way to get the output of that and place it into pashua run would be cool, on the fly: I.E load te contents of TEST.txt and generate the place it into pashua_run, I've tried using cat and opening the file... but because it's in Pashua_run it doesn't work, is there a smart way to break out then back in? Or the second way which I was thinking, was create get the output then append it into the middle text file containing the pashua runtime, then execute it, maybe slightly hacky, but I would imagine it will do the job. Any ideas? ++ I know I probably could make my life a lot easier, by doing this in actionscript and cocoa, although at present don't have time for such a learning curve, although I do plan to get round to it.

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  • Auto update the content in ASP.NET

    - by Zerotoinfinite
    I have to design a website where user can update their status, just like facebook and twitter and other social networking sites. Now my requirement is to refresh the feed with new user updates. Ex: when the new status comes facebook automatically add that on the top of the feed. on the other hand twitter shows the number of updates which is ready to be load. both ways are acceptable to me Now, I have to decide what is the best way to achieve this functionality. I am open to use ASP.NET. So I am confused that regular repeater control with timer and auto refresh or any other way? (I am wondering that if I set repeater for auto update and meanwhile if user is performing some action on any status it will lost). or do I need to change my framework from ASP.NET to ASP.NET MVC (I am little afraid with MVC as I have very less knowledge regarding it and I know it has a learning curve to master ajax/Jquery things) Any suggestion how I can I achieve it in a better and feasible way? EDIT1 I am not looking for a code but I want advice to achieve this. Supporting URL's would be appreciated. EDIT2 I am open to JQuery which can regularly check the database and fill the section. But my concern is this that if user is updating any comment and want to load/feed is automatically generated. his textbox text shouldn't be disappear (just like facebook, twitter or Linkedin) EDIT3 I have seen that on Stack overflow when any other user has modified the question/answer, I got notification like this question/answer is modified. and when I clicked on that notification only that section got reloaded. I am curious to know how to achieve this functionality. So that when user is commenting on a status/post and if meanwhile someone has updated the content then it would show the other user comment. Edit4 Could someone please recommend me an example of ASP.NET MVC 3+ which can do similar kind of activity (i.e. one input box and once user insert an text it will add the item in the list (with JQuery).

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  • Queue ExternalInterface calls to Flash Object in UpdatePanel - Needs Improvement?

    - by Laramie
    A Flash (actually Flex) object is created on an ASP.Net page within an Update Panel using a modified version of the embedCallAC_FL_RunContent.js script so it can be written in dynamically. It is re-created with this script with each partial postback to that panel. There are also other Update Panels on the page. With some postbacks (partial and full), External Interface calls such as $get('FlashObj').ExternalInterfaceFunc('arg1', 0, true); are prepared server-side and added to the page using ScriptManager.RegisterStartupScript. They're embedded in a function and stuffed into Sys.Application's load event, for example Sys.Application.add_load(funcContainingExternalInterfaceCalls). The problem is that because the Flash object's state state may change with each partial postback, the Flash (Flex) object and/or External Interface may not be ready or even exist yet in the DOM when the JavaScript - Flash External Interface call is made. It results in an "Object doesn't support this property or method" exception. I have a working strategy to make the ExternalInterface calls immediately if Flash is ready or else queue them until such time that Flash announces its readiness. //Called when the Flash object is initialized and can accept ExternalInterfaceCalls var flashReady = false; //Called by Flash when object is fully initialized function setFlashReady() { flashReady = true; //Make any queued ExternalInterface calls, then dequeue while (extIntQueue.length > 0) (extIntQueue.shift())(); } var extIntQueue = []; function callExternalInterface(flashObjName, funcName, args) { //reference to the wrapped ExternalInterface Call var wrapped = extWrap(flashObjName, funcName, args); //only procede with ExternalInterface call if the global flashReady variable has been set if (flashReady) { wrapped(); } else { //queue the function so when flashReady() is called next, the function is called and the aruments are passed. extIntQueue.push(wrapped); } } //bundle ExtInt call and hold variables in a closure function extWrap(flashObjName, funcName, args) { //put vars in closure return function() { var funcCall = '$get("' + flashObjName + '").' + funcName; eval(funcCall).apply(this, args); } } I set the flashReady var to dirty whenever I update the Update Panel that contains the Flash (Flex) object. ScriptManager.RegisterClientScriptBlock(parentContainer, parentContainer.GetType(), "flashReady", "flashReady = false;", true); I'm pleased that I got it to work, but it feels like a hack. I am still on the learning curve with respect to concepts like closures why "eval()" is apparently evil, so I'm wondering if I'm violating some best practice or if this code should be improved, if so how? Thanks.

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  • How hard programming is? Really. [closed]

    - by Bubba88
    Hi! The question is about your perception of programming activity. How hard/exacting this task is? There is much buzz about programming nowadays, people say that programmers are smart, very technical and abstract at a time, know much about world, psychology etc.. They say, that programmers got really powerful brain thing, cause there is much to keep in consideration simultaneously again with much information folded into each other associatively (up 10 levels of folding they say))) Still, there are some terms to specify at our own.. So that is the question: What do you think about programming in general? Is it hard? Is it 'for everyone' or for the particular kind of people only? How much non-CS background do you need to program (just to program, really; enterprise applications for example)? How long is the learning curve? (again, for programming in general) And another bunch of random questions: - If you were not to like/love programming, would that be a serious trouble bothering your current employment? - If you were to start from the beginning, would you chose that direction this time? - What other areas (jobs or maybe hobbies) are comparable to programming in the way they can explode someone's lovely brain? - Is 'non turing-complete programming' (SQL, XML, etc.) comparable to what we do or is it really way easier, less requiring, cheap and akin to cooking :)? Well, the essence is: How would you describe programming activity WRT to its difficulty? Or, on the other hand: Did you ever catch yourself thinking at some point: OMG, it's sooo hard! I don't know how would I ever program, even carried away this way and doing programming just for fun? It's very interesting to know your opinion, your'e the programmers after all. I mean much people must be exaggerating/speculating about the thing they do not really know about. But that musn't be the case here on SO :) P.S.: I'll try my best to update this post later, and you please edit it too. At least I'll get decent English in my question text :)

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  • DCVS + hosting for a startup commercial multiplatform phone app

    - by AG
    I'm in lean startup mode, working on a simple phone app that will be published initially as a iThingy app and an Android app with, possibly, Blackberry and Symbian versions to follow. I'm about to go from no repository to needing a central repository that up to 4 very part-time resources will be sharing. Two of us have no version control background, one has used Subversion, and I've used most of the major centralized VCS systems. I'm not going to be pushing the technical limitations of any VCS for a long time; I'm sure that any of the major systems would work fine. And the hosting accounts I've looked at seem reasonable. So I'm really focussed on minimizing the downside risks. That is, I'd like to find a stable setup that is easy to learn in general, easy to use from Windows/Eclipse, and won't paint me into any obvious corners for the next 12 months or so. A quick search of the web had led me to consider the following pairs of DVCS and hosting service, with what I think I'm hearing as their strengths and weaknesses (for my purposes): Bazaar/Launchpad -- My initial choice since I need to get more familiar with this pair for the Google Summer of Code mentoring I'm doing. But, whatever the technical merits, a non-starter for me because they are purely open source, no private repositories plans to purchase that I can see. Git/GitHub -- Git: Fast, light, ultimately flexible, but relatively less Windows friendly, Eclipse plugin (eGit) available but relatively young, GitHub: widely used, pricing is fine Mercurial/BitBucket -- Mercurial: a little less flexible, a little more Windows friendly, Eclipse plugin seems a bit more mature, BitBucket: widely used, pricing is fine, includes a wiki and an issue tracker that we might be able to use instead of something like BaseCamp, at least for a while. Mercurial/BitBucket seem like the winning pair so far for my particular situation; at least two of us are definitely going to be working mostly from Eclipse on Windows and reducing my own learning curve is a priority. ;-) But I have two specific questions: 1) Am I wrong about Bazaar/Launchpad and is there a viable, secure way to use them for proprietary code? 2) Any reason to think that the Mecurial/Bitbucket pair will end up being a headache for my Mac developer, soon, or for Blackberry or Symbian developers a little later? ag

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  • RAD Visual Web Application Creator/ Builder/ Designer for PHP

    - by inhoue
    Hi all, I want to see if any of you know a (free and open source will be ideal) tool/ app that can help build a php web application very quickly without investing too much time on writing codes, preferring drag and drop/ point and click work-flow designer for logic design (see Agile from Outsystems below). Plus, visual designer for the business logic is great since it can help a developer visualize the logic better. There are a lot of GUI builders, form builders out there, but I am looking for one app for the entire web application development process. My goal is to find an application that a team of developers can use together and use the build-in code of the app as much as possible. E.g. the app will provide a modular just for handle user login or a shopping cart; a developer just need to drag and drop the modular to the logic designer and the code will be generated. This way the functionality will be in a module and code will always be standard across developers. So if a new developer get on-board, he will just need to use the system and get up and running quickly. To explain this better: there is a lot php frameworks, e.g. cakephp, CodeIgniter, etc which I can use to help coding, but still I need to create (code) the GUI, writing quite a bit of codes. I am looking for a tool/ app that is a little more high level than those frameworks. Here is 2 examples apps I found during my google search which they have visual logic designer and gui builder in one single app. Also a single click deployment (but I need it to be php apps or at least I can deploy the (php) code to a LAMP/ WAMP server): Wavemaker: for JAVA Agile from Outsystems: for JAVA or .net (This one is really good, with work-flow drag and drop logic designer!) Talend: it is just an ETL tool, but the concept is what I want to bring up. Drag and drop, point and click logic design. Custom code can be added if it is needed, but the drag and drop process already finished the structure and most of the coding of the web app one needs to build. I want to list Adobe Flex, but it is more like a GUI designer + IDE, not exactly what I want to describe here. The drag and drop/ work-flow logic designer is a key for the app. I could go for the CMS route by learning how to extend them, but it is not that flexible for me and is a long learning curve. Anybody came across this type of app before? Or any idea of how can I find those apps? I googled them for long time, I don't see any of them for php and just few (just 2) for Java. Thanks in advance!

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  • Android library to get pitch from WAV file

    - by Sakura
    I have a list of sampled data from the WAV file. I would like to pass in these values into a library and get the frequency of the music played in the WAV file. For now, I will have 1 frequency in the WAV file and I would like to find a library that is compatible with Android. I understand that I need to use FFT to get the frequency domain. Is there any good libraries for that? I found that [KissFFT][1] is quite popular but I am not very sure how compatible it is on Android. Is there an easier and good library that can perform the task I want? EDIT: I tried to use JTransforms to get the FFT of the WAV file but always failed at getting the correct frequency of the file. Currently, the WAV file contains sine curve of 440Hz, music note A4. However, I got the result as 441. Then I tried to get the frequency of G4, I got the result as 882Hz which is incorrect. The frequency of G4 is supposed to be 783Hz. Could it be due to not enough samples? If yes, how much samples should I take? //DFT DoubleFFT_1D fft = new DoubleFFT_1D(numOfFrames); double max_fftval = -1; int max_i = -1; double[] fftData = new double[numOfFrames * 2]; for (int i = 0; i < numOfFrames; i++) { // copying audio data to the fft data buffer, imaginary part is 0 fftData[2 * i] = buffer[i]; fftData[2 * i + 1] = 0; } fft.complexForward(fftData); for (int i = 0; i < fftData.length; i += 2) { // complex numbers -> vectors, so we compute the length of the vector, which is sqrt(realpart^2+imaginarypart^2) double vlen = Math.sqrt((fftData[i] * fftData[i]) + (fftData[i + 1] * fftData[i + 1])); //fd.append(Double.toString(vlen)); // fd.append(","); if (max_fftval < vlen) { // if this length is bigger than our stored biggest length max_fftval = vlen; max_i = i; } } //double dominantFreq = ((double)max_i / fftData.length) * sampleRate; double dominantFreq = (max_i/2.0) * sampleRate / numOfFrames; fd.append(Double.toString(dominantFreq)); Can someone help me out? EDIT2: I manage to fix the problem mentioned above by increasing the number of samples to 100000, however, sometimes I am getting the overtones as the frequency. Any idea how to fix it? Should I use Harmonic Product Frequency or Autocorrelation algorithms?

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  • In Linux, what's the best way to delegate administration responsibilities, like for Apache, a database, or some other application?

    - by Andrew Banks
    In Linux, what's the best way to delegate administration responsibilities for Apache and other "applications"? File permissions? Sudo? A mix of both? Something else? At work we have two tiers of "administrators" Operating system administrators. These are your run-of-the-mill "server administrators." They are responsible for just the operating system. Application administrators. The people who build the web site. This includes not only writing the SQL, PHP, and HTML, but also setting up and running Apache and PostgreSQL or MySQL. The aforementioned OS admins will install this stuff, but it's mainly up to the app admins to edit all the config files, start and stop processes when needed, and so on. I am one of the app admins. This is different than what I am used to. I used to just write code. The sysadmin took care not only of the OS but also installing, setting up, and keeping up the server software. But he left. Now I'm in charge of setting up Apache and the database. The new sysadmins say they just handle the operating system. It's no problem. I welcome learning new stuff. But there is a learning curve, even for the OS admins. Apache, by default, seems to be set up for administration by root directly. All the config files and scripts are 644 and owned by root:root. I'm not given the root password, naturally, so the OS admins must somehow give my ordinary OS user account all the rights necessary to edit Apache's config files, start and stop it, read its log files, and so on. Right now they're using a mix of: (1) giving me certain sudo rights, (2) adding me to certain groups, and (3) changing the file permissions of various directories, to make them writable by one of the groups I'm in. This never goes smoothly. There's always a back-and-forth between me and the sysadmins. They say it's ready. Then I try certain things, and half of them I still can't do. So they make some more changes. Then finally I seem to be independent and can administer Apache and the database without pestering them anymore. It's the sheer complication and amount of changes that make me uncomfortable. Even though it finally works, more or less, it seems hackneyed. I feel like we're doing it wrong. It seems like the makers of the software would have anticipated this scenario (someone other than root administering it) and have a clean two- or three-step program to delegate responsibility to me. But it feels like we are really chewing up the filesystem and making it far and away from the default set-up. Any suggestions? Are we doing it the recommended way? P.S. For PostgreSQL it seems a little better. Its files are owned by a system user named postgres. So giving me the right to run sudo su - postgres gives me just about everything. I'm just now getting into MySQL, but it seems to be set up similarly. But it seems a little weird doing all my work as another user.

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  • Cloud MBaaS : The Next Big Thing in Enterprise Mobility

    - by shiju
    In this blog post, I will take a look at Cloud Mobile Backend as a Service (MBaaS) and how we can leverage Cloud based Mobile Backend as a Service for building enterprise mobile apps. Today, mobile apps are incredibly significant in both consumer and enterprise space and the demand for the mobile apps is unbelievably increasing in day to day business. An enterprise can’t survive in business without a proper mobility strategy. A better mobility strategy and faster delivery of your mobile apps will give you an extra mileage for your business and IT strategy. So organizations and mobile developers are looking for different strategy for meeting this demand and adopting different development strategy for their mobile apps. Some developers are adopting hybrid mobile app development platforms, for delivering their products for multiple platforms, for fast time-to-market. Others are adopting a Mobile enterprise application platform (MEAP) such as Kony for their enterprise mobile apps for fast time-to-market and better business integration. The Challenges of Enterprise Mobility The real challenge of enterprise mobile apps, is not about creating the front-end environment or developing front-end for multiple platforms. The most important thing of enterprise mobile apps is to expose your enterprise data to mobile devices where the real pain is your business data might be residing in lot of different systems including legacy systems, ERP systems etc., and these systems will be deployed with lot of security restrictions. Exposing your data from the on-premises servers, is not a easy thing for most of the business organizations. Many organizations are spending too much time for their front-end development strategy, but they are really lacking for building a strategy on their back-end for exposing the business data to mobile apps. So building a REST services layer and mobile back-end services, on the top of legacy systems and existing middleware systems, is the key part of most of the enterprise mobile apps, where multiple mobile platforms can easily consume these REST services and other mobile back-end services for building mobile apps. For some mobile apps, we can’t predict its user base, especially for products where customers can gradually increase at any time. And for today’s mobile apps, faster time-to-market is very critical so that spending too much time for mobile app’s scalability, will not be worth. The real power of Cloud is the agility and on-demand scalability, where we can scale-up and scale-down our applications very easily. It would be great if we could use the power of Cloud to mobile apps. So using Cloud for mobile apps is a natural fit, where we can use Cloud as the storage for mobile apps and hosting mechanism for mobile back-end services, where we can enjoy the full power of Cloud with greater level of on-demand scalability and operational agility. So Cloud based Mobile Backend as a Service is great choice for building enterprise mobile apps, where enterprises can enjoy the massive scalability power of their mobile apps, provided by public cloud vendors such as Microsoft Windows Azure. Mobile Backend as a Service (MBaaS) We have discussed the key challenges of enterprise mobile apps and how we can leverage Cloud for hosting mobile backend services. MBaaS is a set of cloud-based, server-side mobile services for multiple mobile platforms and HTML5 platform, which can be used as a backend for your mobile apps with the scalability power of Cloud. The information below provides the key features of a typical MBaaS platform: Cloud based storage for your application data. Automatic REST API services on the application data, for CRUD operations. Native push notification services with massive scalability power. User management services for authenticate users. User authentication via Social accounts such as Facebook, Google, Microsoft, and Twitter. Scheduler services for periodically sending data to mobile devices. Native SDKs for multiple mobile platforms such as Windows Phone and Windows Store, Android, Apple iOS, and HTML5, for easily accessing the mobile services from mobile apps, with better security.  Typically, a MBaaS platform will provide native SDKs for multiple mobile platforms so that we can easily consume the server-side mobile services. MBaaS based REST APIs can use for integrating to enterprise backend systems. We can use the same mobile services for multiple platform so hat we can reuse the application logic to multiple mobile platforms. Public cloud vendors are building the mobile services on the top of their PaaS offerings. Windows Azure Mobile Services is a great platform for a MBaaS offering that is leveraging Windows Azure Cloud platform’s PaaS capabilities. Hybrid mobile development platform Titanium provides their own MBaaS services. LoopBack is a new MBaaS service provided by Node.js consulting firm StrongLoop, which can be hosted on multiple cloud platforms and also for on-premises servers. The Challenges of MBaaS Solutions If you are building your mobile apps with a new data storage, it will be very easy, since there is not any integration challenges you have to face. But most of the use cases, you have to extract your application data in which stored in on-premises servers which might be under VPNs and firewalls. So exposing these data to your MBaaS solution with a proper security would be a big challenge. The capability of your MBaaS vendor is very important as you have to interact with your legacy systems for many enterprise mobile apps. So you should be very careful about choosing for MBaaS vendor. At the same time, you should have a proper strategy for mobilizing your application data which stored in on-premises legacy systems, where your solution architecture and strategy is more important than platforms and tools.  Windows Azure Mobile Services Windows Azure Mobile Services is an MBaaS offerings from Windows Azure cloud platform. IMHO, Microsoft Windows Azure is the best PaaS platform in the Cloud space. Windows Azure Mobile Services extends the PaaS capabilities of Windows Azure, to mobile devices, which can be used as a cloud backend for your mobile apps, which will provide global availability and reach for your mobile apps. Windows Azure Mobile Services provides storage services, user management with social network integration, push notification services and scheduler services and provides native SDKs for all major mobile platforms and HTML5. In Windows Azure Mobile Services, you can write server-side scripts in Node.js where you can enjoy the full power of Node.js including the use of NPM modules for your server-side scripts. In the previous section, we had discussed some challenges of MBaaS solutions. You can leverage Windows Azure Cloud platform for solving many challenges regarding with enterprise mobility. The entire Windows Azure platform can play a key role for working as the backend for your mobile apps where you can leverage the entire Windows Azure platform for your mobile apps. With Windows Azure, you can easily connect to your on-premises systems which is a key thing for mobile backend solutions. Another key point is that Windows Azure provides better integration with services like Active Directory, which makes Windows Azure as the de facto platform for enterprise mobility, for enterprises, who have been leveraging Microsoft ecosystem for their application and IT infrastructure. Windows Azure Mobile Services  is going to next evolution where you can expect some exciting features in near future. One area, where Windows Azure Mobile Services should definitely need an improvement, is about the default storage mechanism in which currently it is depends on SQL Server. IMHO, developers should be able to choose multiple default storage option when creating a new mobile service instance. Let’s say, there should be a different storage providers such as SQL Server storage provider and Table storage provider where developers should be able to choose their choice of storage provider when creating a new mobile services project. I have been used Windows Azure and Windows Azure Mobile Services as the backend for production apps for mobile, where it performed very well. MBaaS Over MEAP Recently, many larger enterprises has been adopted Mobile enterprise application platform (MEAP) for their mobile apps. I haven’t worked on any production MEAP solution, but I heard that developers are really struggling with MEAP in different way. The learning curve for a proprietary MEAP platform is very high. I am completely against for using larger proprietary ecosystem for mobile apps. For enterprise mobile apps, I highly recommend to use native iOS/Android/Windows Phone or HTML5  for front-end with a cloud hosted MBaaS solution as the middleware. A MBaaS service can be consumed from multiple mobile apps where REST APIs are using to integrating with enterprise backend systems. Enterprise mobility should start with exposing REST APIs on the enterprise backend systems and these REST APIs can host on Cloud where we can enjoy the power of Cloud for our services. If you are having REST APIs for your enterprise data, then you can easily build mobile frontends for multiple platforms.   You can follow me on Twitter @shijucv

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  • On Her Majesty's Secret Source Code: .NET Reflector 7 Early Access Builds Now Available

    - by Bart Read
    Dodgy Bond references aside, I'm extremely happy to be able to tell you that we've just released our first .NET Reflector 7 Early Access build. We're going to make these available over the coming weeks via the main .NET Reflector download page at: http://reflector.red-gate.com/Download.aspx Please have a play and tell us what you think in the forum we've set up. Also, please let us know if you run into any problems in the same place. The new version so far comes with numerous decompilation improvements including (after 5 years!) support for iterator blocks - i.e., the yield statement first seen in .NET 2.0. We've also done a lot of work to solidify the support for .NET 4.0. Clive's written about the work he's done to support iterator blocks in much more detail here, along with the odd problem he's encountered when dealing with compiler generated code: http://www.simple-talk.com/community/blogs/clivet/96199.aspx. On the UI front we've started what will ultimately be a rewrite of the entire front-end, albeit broken into stages over two or three major releases. The most obvious addition at the moment is tabbed browsing, which you can see in Figure 1. Figure 1. .NET Reflector's new tabbed decompilation feature. Use CTRL+Click on any item in the assembly browser tree, or any link in the source code view, to open it in a new tab. This isn't by any means finished. I'll be tying up loose ends for the next few weeks, with a major focus on performance and resource usage. .NET Reflector has historically been a largely single-threaded application which has been fine up until now but, as you might expect, the addition of browser-style tabbing has pushed this approach somewhat beyond its limit. You can see this if you refresh the assemblies list by hitting F5. This shows up another problem: we really need to make Reflector remember everything you had open before you refreshed the list, rather than just the last item you viewed - I discovered that it's always done the latter, but it used to hide all panes apart from the treeview after a Refresh, including the decompiler/disassembler window. Ultimately I've got plans to add the whole VS/Chrome/Firefox style ability to drag a tab into the middle of nowhere to spawn a new window, but I need to be mindful of the add-ins, amongst other things, so it's possible that might slip to a 7.5 or 8.0 release. You'll also notice that .NET Reflector 7 now needs .NET 3.5 or later to run. We made this jump because we wanted to offer ourselves a much better chance of adding some really cool functionality to support newer technologies, such as Silverlight and Windows Phone 7. We've also taken the opportunity to start using WPF for UI development, which has frankly been a godsend. The learning curve is practically vertical but, I kid you not, it's just a far better world. Really. Stop using WinForms. Now. Why are you still using it? I had to go back and work on an old WinForms dialog for an hour or two yesterday and it really made me wince. The point is we'll be able to move the UI in some exciting new directions that will make Reflector easier to use whilst continuing to develop its functionality without (and this is key) cluttering the interface. The 3.5 language enhancements should also enable us to be much more productive over the longer term. I know most of you have .NET Fx 3.5 or 4.0 already but, if you do need to install a new version, I'd recommend you jump straight to 4.0 because, for one thing, it's faster, and if you're starting afresh there's really no reason not to. Despite the Fx version jump the Visual Studio add-in should still work fine in Visual Studio 2005, and obviously will continue to work in Visual Studio 2008 and 2010. If you do run into problems, again, please let us know here. As before, we continue to support every edition of Visual Studio exception the Express Editions. Speaking of Visual Studio, we've also been improving the add-in. You can now open and explore decompiled code for any referenced assembly in any project in your solution. Just right-click on the reference, then click Decompile and Explore on the context menu. Reflector will pop up a progress box whilst it decompiles your assembly (Figure 2) - you can move this out of the way whilst you carry on working. Figure 2. Decompilation progress. This isn't modal so you can just move it out of the way and carry on working. Once it's done you can explore your assembly in the Reflector treeview (Figure 3), also accessible via the .NET Reflector Explore Decompiled Assemblies main menu item. Double-click on any item to open decompiled source in the Visual Studio source code view. Use right-click and Go To Definition on the source view context menu to navigate through the code. Figure 3. Using the .NET Reflector treeview within Visual Studio. Double-click on any item to open decompiled source in the source code view. There are loads of other changes and fixes that have gone in, often under the hood, which I don't have room to talk about here, and plenty more to come over the next few weeks. I'll try to keep you abreast of new functionality and changes as they go in. There are a couple of smaller things worth mentioning now though. Firstly, we've reorganised the menus and toolbar in Reflector itself to more closely mirror what you might be used to in other applications. Secondly, we've tried to make some of the functionality more discoverable. For example, you can now switch decompilation target framework version directly from the toolbar - and the default is now .NET 4.0. I think that about covers it for the moment. As I said, please use the new version, and send us your feedback. Here's that download URL again: http://reflector.red-gate.com/Download.aspx. Until next time! Technorati Tags: .net reflector,7,early access,new version,decompilation,tabbing,visual studio,software development,.net,c#,vb

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  • SharePoint – The Most Important Feature

    - by Bil Simser
    Watching twitter and doing a search for SharePoint and you see a lot (almost one every few minutes) of tweets about the top 10 new features in SharePoint. What answer do you get when you ask the question, “What’s the most important feature in SharePoint?”. Chances are the answer will vary. Some will say it’s the collaboration aspect, others might say it’s the new ribbon interface, multi-item editing, external content types, faceted search, large list support, document versioning, Silverlight, etc. The list goes on. However I think most people might be missing the most important feature that’s sitting right under their noses all this time. The most important feature of SharePoint? It’s called User Empowerment. Huh? What? Is that something I find in the Site Actions menu? Nope. It’s something that’s always been there in SharePoint, you just need to get the word out and support it. How many times have you had a team ask you for a team site (assuming you had SharePoint up and running). Or to create them a contact list. Or how long have you employed that guy in the corner who’s been copying and pasting content from Corporate Communications into the web from a Word document. Let’s stop the insanity. It doesn’t have to be this way. SharePoint’s strongest feature isn’t anything you can find in the Site Settings screen or Central Admin. It’s all about empowering your users and letting them take control of their content. After all, SharePoint really is a bunch of tools to allow users to collaborate on content isn’t it? So why are you stepping in as IT and helping the user every moment along the way. It’s like having to ask users to fill out a help desk ticket or call up the Windows team to create a folder on their desktop or rearrange their Start menu. This isn’t something IT should be spending their time doing nor is it something the users should be burdened with having to wait until their friendly neighborhood tech-guy (or gal) shows up to help them sort the icons on their desktop. SharePoint IS all about empowerment. Site owners can create whatever lists and libraries they need for their team, and if the template isn’t there they can always turn to my friend and yours, the Custom List. From that can spew forth approval tracking systems, new hire checklists, and server inventory. You’re only limited by your imagination and needs. Users should be able to create new sites as they need. Want a blog to let everyone know what your team is up to? Go create one, here’s how. What’s a blog you ask? Here’s what it is and why you would use one. SharePoint is the shift in the balance of power and you need, and an IT group, let go of certain responsibilities and let your users run with the tools. A power user who knows how to create sites and what features are available to them can help a team go from the forming stage to the storming stage overnight. Again, this all hinges on you as an IT organization and what you can and empower your users with as far as features go. Running with tools is great if you know how to use them, running with scissors not recommended unless you enjoy trips to the hospital. With Great Power comes Great Responsibility so don’t go out on Monday and send out a memo to the organization saying “This Bil guy says you peeps can do anything so here it is, knock yourself out” (for one, they’ll have *no* idea who this Bil guy is). This advice comes with the task of getting your users ready for empowerment. Whether it’s through some kind of internal training sessions, in-house documentation; videos; blog posts; on how to accomplish things in SharePoint, or full blown one-on-one sit downs with teams or individuals to help them through their problems. The work is up to you. Helping them along also should be part of your governance (you do have one don’t you?). Just because you have InfoPath client deployed with your Office suite, doesn’t mean users should just start publishing forms all over your SharePoint farm. There should be some governance behind that in what you’ll support and what is possible. The other caveat to all this is that SharePoint is not everything for everyone. It can’t cook you breakfast and impregnate your cat or solve world hunger. It also isn’t suited for every IT solution out there. It’s a horrible source control system (even though some people try to use it as such) and really can’t do financials worth a darn. Again, governance is key here and part of that governance and your responsibility in setting up and unleashing SharePoint into your organization is to provide users guidance on what should be in SharePoint and (more importantly) what should not be in SharePoint. There are boundaries you have to set where you don’t want your end users going as they might be treading into trouble. Again, this is up to you to set these constraints and help users understand why these pylons are there. If someone understands why they can’t do something they might have a better understanding and respect for those that put them there in the first place. Of course you’ll always have the power-users who want to go skiing down dead mans curve so this doesn’t work for everyone, but you can catch the majority of the newbs who don’t wander aimlessly off the beaten path. At the end of the day when all things are going swimmingly your end users should be empowered to solve the needs they have on a day to day basis and not having to keep bugging the IT department to help them create a view to show only approved documents. I wouldn’t go as far as business users building out full blown solutions and handing the keys to SharePoint Designer or (worse) Visual Studio to power-users might not be a path you want to go down but you also don’t have to lock up the SharePoint system in a tight box where users can’t use what’s there. So stop focusing on the shiny things in SharePoint and maybe consider making a shift to what’s really important. Making your day job easier and letting users get the most our of your technology investment.

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  • Visiting the Emtel Data Centre

    Back in February at the first event of the Emtel Knowledge Series (EKS) I spoke to various people at Emtel about their data centre here on the island. I was trying to see whether it would be possible to arrange a meeting over there for a selected group of our community members. Well, let's say it like this... My first approach wasn't that promising and far from successful but during the following months there were more and more occasions to get in touch with the "right" contact persons at Emtel to make it happen... Setting up an appointment and pre-requisites The major improvement came during a Boot Camp for Windows Phone 8.1 App development organised by Microsoft Indian Ocean Islands in cooperation with Emtel at the Emtel World, Ebene. Apart from learning bits and pieces regarding Universal Apps I took the opportunity to get in touch with Arvin Lockee, Sales Executive - Data, during our lunch break. And this really kicked off the whole procedure. Prior to get access to the Emtel data centre it is requested that you provide full name and National ID of anyone going to visit. Also, it should be noted that there was only a limited amount of seats available. Anyways, packed with this information I posted through the usual social media channels. Responses came in very quickly and based on First-come, first-serve (FCFS) principle I noted down the details and forwarded them to Emtel in order to fix a date and time for the visit. In preparation on our side, all attendees exchanged contact details and we organised transport options to go to the data centre in Arsenal. The day before and on the day of our meeting, Arvin send me a reminder to check whether everything is still confirmed and ready to go... Of course, it was! Arriving at the Emtel Data Centre As I'm coming from Flic En Flac towards the North, we agreed that I'm going to pick up a couple of young fellows near the old post office in Port Louis. All went well, except that Sean eventually might be living in another time zone compared to the rest of us. Anyway, after some extended stop we were complete and arrived just in time in Arsenal to meet and greet with Ish and Veer. Again, Emtel is taking access procedures to their data centre very serious and the gate stayed close until all our IDs had been noted and compared to the list of registered attendees. Despite having a good laugh at the mixture of old and new ID cards it was a straight-forward processing. The ward was very helpful and guided us to the waiting area at the entrance section of the building. Shortly after we were welcomed by Kamlesh Bokhoree, the Data Centre Officer. He gave us brief introduction into the rules and regulations during our visit, like no photography allowed, not touching the buttons, and following his instructions through the whole visit. Of course! Inside the data centre Next, he explained us the multi-factor authentication system using a combination of bio-metric data, like finger print reader, and "classic" pin panel. The Emtel data centre provides multiple services and next to co-location for your own hardware they also offer storage options for your backup and archive data in their massive, fire-resistant vault. Very impressive to get to know about the considerations that have been done in choosing the right location and how to set up the whole premises. It should also be noted that there is 24/7 CCTV surveillance inside and outside the buildings. Strengths of the Emtel TIER 3 Data Centre, Mauritius Finally, we were guided into the first server room. And wow, the whole setup is cleverly planned and outlined in the architecture. From the false floor and ceilings in order to provide optimum air flow, over to the separation of cold and hot aisles between the full-size server racks, and of course the monitored air conditions in order to analyse and watch changes in temperature, smoke detection and other parameters. And not surprisingly everything has been implemented in two independent circuits. There is a standardised classification for the construction and operation of data centres world-wide, and the Emtel's one has been designed to be a TIER 4 building but due to the lack of an alternative power supplier on the island it is officially registered as a TIER 3 compliant data centre. Maybe in the long run there might be a second supplier of energy next to CEB... time will tell. Luckily, the data centre is integrated into the National Fibre Optic Gigabit Ring and Emtel already connects internationally through diverse undersea cable routes like SAFE & LION/LION2 out of Mauritius and through several other providers for onwards connectivity. The data centre is part of the National Fibre Optic Gigabit Ring and has redundant internet connectivity onwards. Meanwhile, Arvin managed to join our little group of geeks and he supported Kamlesh in answering our technical questions regarding the capacities and general operation of the data centre. Visiting the NOC and its dedicated team of IT professionals was surely one of the visual highlights. Seeing their wall of screens to monitor any kind of activities on the data lines, the managed servers and the activity in and around the building was great. Even though I'm using a multi-head setup since years I cannot keep it up with that setup... ;-) But I got a couple of ideas on how to improve my work spaces here at the office. Clear advantages of hosting your e-commerce and mobile backends locally After the completely isolated NOC area we continued our Q&A session with Kamlesh and Arvin in the second server room which is dedictated to shared environments. On first thought it should be well-noted that there is lots of space for full-sized racks and therefore co-location of your own hardware. Actually, given the feedback that there will be upcoming changes in prices the facilities at the Emtel data centre are getting more and more competitive and interesting for local companies, especially small and medium enterprises. After seeing this world-class infrastructure available on the island, I'm already considering of moving one of my root servers abroad to be co-located here on the island. This would provide an improved user experience in terms of site performance and latency. This would be a good improvement, especially for upcoming e-commerce solutions for two of my local clients. Later on, we actually started the conversation of additional services that could be a catalyst for the local market in order to attract more small and medium companies to take the data centre into their evaluations regarding online activities. Until today Emtel does not provide virtualised server environments but there might be ongoing plans in the future to cover this field as well. Emtel is a mobile operator and internet connectivity provider in the first place, entering a market of managed and virtualised server infrastructures including capacities in terms of cloud storage and computing are rather new and there is a continuous learning curve at Emtel, too. You cannot just jump into a new market and see how it works out... And I appreciate Emtel's approach towards a solid fundament and then building new services on top of that. Emtel as a future one-stop-shop service provider for all your internet and telecommunications needs. Emtel's promotional video about their TIER 3 data centre in Arsenal, Mauritius More details are thoroughly described in Emtel's brochure of their data centre. Check out their PDF document here. Thanks for this opportunity Visiting and walking through the Emtel data centre for more than 2 hours was a great experience. As representative of the Mauritius Software Craftsmanship Community (MSCC) I would like to thank anyone at Emtel involved in the process of making it happen, and especially to Arvin Lockee and Kamlesh Bokhoree for their time and patience in explaining the infrastructure and answering all the endless questions from our members. Thank You!

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  • DialogFX: A New Approach to JavaFX Dialogs

    - by HecklerMark
    How would you like a quick and easy drop-in dialog box capability for JavaFX? That's what I was thinking when a weekend presented itself. And never being one to waste a good weekend...  :-) After doing some "roll-your-own" basic dialog building for a JavaFX app, I recently stumbled across Anton Smirnov's work on GitHub. It was a good start, but it wasn't exactly what I was after, and ideas just kept popping up of things I'd do differently. I wanted something a bit more streamlined, a bit easier to just "drop in and use". And so DialogFX was born. DialogFX wasn't intended to be overly fancy, overly clever - just useful and robust. Here were my goals: Easy to use. A dialog "system" should be so simple to use a new developer can drop it in quickly with nearly no learning curve. A seasoned developer shouldn't even have to think, just tap in a few lines and go. Why should dialogs slow "actual development"?  :-) Defaults. If you don't specify something (dialog type, buttons, etc.), a good dialog system should still work. It may not be pretty, but it shouldn't throw gears. Sharable. It's all open source. Even the icons are in the commons, so they can be reused at will. Let's take a look at some screen captures and the code used to produce them.   DialogFX INFO dialog Screen captures Windows Mac  Sample code         DialogFX dialog = new DialogFX();        dialog.setTitleText("Info Dialog Box Example");        dialog.setMessage("This is an example of an INFO dialog box, created using DialogFX.");        dialog.showDialog(); DialogFX ERROR dialog Screen captures Windows Mac  Sample code         DialogFX dialog = new DialogFX(Type.ERROR);        dialog.setTitleText("Error Dialog Box Example");        dialog.setMessage("This is an example of an ERROR dialog box, created using DialogFX.");        dialog.showDialog(); DialogFX ACCEPT dialog Screen captures Windows Mac  Sample code         DialogFX dialog = new DialogFX(Type.ACCEPT);        dialog.setTitleText("Accept Dialog Box Example");        dialog.setMessage("This is an example of an ACCEPT dialog box, created using DialogFX.");        dialog.showDialog(); DialogFX Question dialog (Yes/No) Screen captures Windows Mac  Sample code         DialogFX dialog = new DialogFX(Type.QUESTION);        dialog.setTitleText("Question Dialog Box Example");        dialog.setMessage("This is an example of an QUESTION dialog box, created using DialogFX. Would you like to continue?");        dialog.showDialog(); DialogFX Question dialog (custom buttons) Screen captures Windows Mac  Sample code         List<String> buttonLabels = new ArrayList<>(2);        buttonLabels.add("Affirmative");        buttonLabels.add("Negative");         DialogFX dialog = new DialogFX(Type.QUESTION);        dialog.setTitleText("Question Dialog Box Example");        dialog.setMessage("This is an example of an QUESTION dialog box, created using DialogFX. This also demonstrates the automatic wrapping of text in DialogFX. Would you like to continue?");        dialog.addButtons(buttonLabels, 0, 1);        dialog.showDialog(); A couple of things to note You may have noticed in that last example the addButtons(buttonLabels, 0, 1) call. You can pass custom button labels in and designate the index of the default button (responding to the ENTER key) and the cancel button (for ESCAPE). Optional parameters, of course, but nice when you may want them. Also, the showDialog() method actually returns the index of the button pressed. Rather than create EventHandlers in the dialog that really have little to do with the dialog itself, you can respond to the user's choice within the calling object. Or not. Again, it's your choice.  :-) And finally, I've Javadoc'ed the code in the main places. Hopefully, this will make it easy to get up and running quickly and with a minimum of fuss. How Do I Get (Git?) It? To try out DialogFX, just point your browser here to the DialogFX GitHub repository and download away! Please take a look, try it out, and let me know what you think. All feedback welcome! All the best, Mark 

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  • Rockmelt, the technology adoption model, and Facebook's spare internet

    - by Roger Hart
    Regardless of how good it is, you'd have to have a heart of stone not to make snide remarks about Rockmelt. After all, on the surface it looks a lot like some people spent two years building a browser instead of just bashing out a Chrome extension over a wet weekend. It probably does some more stuff. I don't know for sure because artificial scarcity is cool, apparently, so the "invitation" is still in the post*. I may in fact never know for sure, because I'm not wild about Facebook sign-in as a prerequisite for anything. From the video, and some initial reviews, my early reaction was: I have a browser, I have a Twitter client; what on earth is this for? The answer, of course, is "not me". Rockmelt is, in a way, quite audacious. Oh, sure, on launch day it's Bay Area bar-chat for the kids with no lenses in their retro specs and trousers that give you deep-vein thrombosis, but it's not really about them. Likewise,  Facebook just launched Google Wave, or something. And all the tech snobbery and scorn packed into describing it that way is irrelevant next to what they're doing with their platform. Here's something I drew in MS Paint** because I don't want to get sued: (see: The technology adoption lifecycle) A while ago in the Guardian, John Lanchester dusted off the idiom that "technology is stuff that doesn't work yet". The rest of the article would be quite interesting if it wasn't largely about MySpace, and he's sort of got a point. If you bolt on the sentiment that risk-averse businessmen like things that work, you've got the essence of Crossing the Chasm. Products for the mainstream market don't look much like technology. Think for  a second about early (1980s ish) hi-fi systems, with all the knobs and fiddly bits, their ostentatious technophile aesthetic. Then consider their sleeker and less (or at least less conspicuously) functional successors in the 1990s. The theory goes that innovators and early adopters like technology, it's a hobby in itself. The rest of the humans seem to like magic boxes with very few buttons that make stuff happen and never trouble them about why. Personally, I consider Apple's maddening insistence that iTunes is an acceptable way to move files around to be more or less morally unacceptable. Most people couldn't care less. Hence Rockmelt, and hence Facebook's continued growth. Rockmelt looks pointless to me, because I aggregate my social gubbins with Digsby, or use TweetDeck. But my use case is different and so are my enthusiasms. If I want to share photos, I'll use Flickr - but Facebook has photo sharing. If I want a short broadcast message, I'll use Twitter - Facebook has status updates. If I want to sell something with relatively little hassle, there's eBay - or Facebook marketplace. YouTube - check, FB Video. Email - messaging. Calendaring apps, yeah there are loads, or FB Events. What if I want to host a simple web page? Sure, they've got pages. Also Notes for blogging, and more games than I can count. This stuff is right there, where millions and millions of users are already, and for what they need it just works. It's not about me, because I'm not in the big juicy area under the curve. It's what 1990s portal sites could never have dreamed of achieving. Facebook is AOL on speed, crack, and some designer drugs it had specially imported from the future. It's a n00b-friendly gateway to the internet that just happens to serve up all the things you want to do online, right where you are. Oh, and everybody else is there too. The price of having all this and the social graph too is that you have all of this, and the social graph too. But plenty of folks have more incisive things to say than me about the whole privacy shebang, and it's not really what I'm talking about. Facebook is maintaining a vast, and fairly fully-featured training-wheels internet. And it makes up a large proportion of the online experience for a lot of people***. It's the entire web (2.0?) experience for the early and late majority. And sure, no individual bit of it is quite as slick or as fully-realised as something like Flickr (which wows me a bit every time I use it. Those guys are good at the web), but it doesn't have to be. It has to be unobtrusively good enough for the regular humans. It has to not feel like technology. This is what Rockmelt sort of is. You're online, you want something nebulously social, and you don't want to faff about with, say, Twitter clients. Wow! There it is on a really distracting sidebar, right in your browser. No effort! Yeah - fish nor fowl, much? It might work, I guess. There may be a demographic who want their social web experience more simply than tech tinkering, and who aren't just getting it from Facebook (or, for that matter, mobile devices). But I'd be surprised. Rockmelt feels like an attempt to grab a slice of Facebook-style "Look! It's right here, where you already are!", but it's still asking the mature market to install a new browser. Presumably this is where that Facebook sign-in predicate comes in handy, though it'll take some potent awareness marketing to make it fly. Meanwhile, Facebook quietly has the entire rest of the internet as a product management resource, and can continue to give most of the people most of what they want. Something that has not gone un-noticed in its potential to look a little sinister. But heck, they might even make Google Wave popular.     *This was true last week when I drafted this post. I got an invite subsequently, hence the screenshot. **MS Paint is no fun any more. It's actually good in Windows 7. Farewell ironically-shonky diagrams. *** It's also behind a single sign-in, lending a veneer of confidence, and partially solving the problem of usernames being crummy unique identifiers. I'll be blogging about that at some point.

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  • Silverlight for Everyone!!

    - by subodhnpushpak
    Someone asked me to compare Silverlight / HTML development. I realized that the question can be answered in many ways: Below is the high level comparison between a HTML /JavaScript client and Silverlight client and why silverlight was chosen over HTML / JavaScript client (based on type of users and major functionalities provided): 1. For end users Browser compatibility Silverlight is a plug-in and requires installation first. However, it does provides consistent look and feel across all browsers. For HTML / DHTML, there is a need to tweak JavaScript for each of the browser supported. In fact, tags like <span> and <div> works differently on different browser / version. So, HTML works on most of the systems but also requires lot of efforts coding-wise to adhere to all standards/ browsers / versions. Out of browser support No support in HTML. Third party tools like  Google gears offers some functionalities but there are lots of issues around platform and accessibility. Out of box support for out-of-browser support. provides features like drag and drop onto application surface. Cut and copy paste in HTML HTML is displayed in browser; which, in turn provides facilities for cut copy and paste. Silverlight (specially 4) provides rich features for cut-copy-paste along with full control over what can be cut copy pasted by end users and .advanced features like visual tree printing. Rich user experience HTML can provide some rich experience by use of some JavaScript libraries like JQuery. However, extensive use of JavaScript combined with various versions of browsers and the supported JavaScript makes the solution cumbersome. Silverlight is meant for RIA experience. User data storage on client end In HTML only small amount of data can be stored that too in cookies. In Silverlight large data may be stored, that too in secure way. This increases the response time. Post back In HTML / JavaScript the post back can be stopped by use of AJAX. Extensive use of AJAX can be a bottleneck as browser stack is used for the calls. Both look and feel and data travel over network.                           In Silverlight everything run the client side. Calls are made to server ONLY for data; which also reduces network traffic in long run. 2. For Developers Coding effort HTML / JavaScript can take considerable amount to code if features (requirements) are rich. For AJAX like interfaces; knowledge of third party kits like DOJO / Yahoo UI / JQuery is required which has steep learning curve. ASP .Net coding world revolves mostly along <table> tags for alignments whereas most popular tools provide <div> tags; which requires lots of tweaking. AJAX calls can be a bottlenecks for performance, if the calls are many. In Silverlight; coding is in C#, which is managed code. XAML is also very intuitive and Blend can be used to provide look and feel. Event handling is much clean than in JavaScript. Provides for many clean patterns like MVVM and composable application. Each call to server is asynchronous in silverlight. AJAX is in built into silverlight. Threading can be done at the client side itself to provide for better responsiveness; etc. Debugging Debugging in HTML / JavaScript is difficult. As JavaScript is interpreted; there is NO compile time error handling. Debugging in Silverlight is very helpful. As it is compiled; it provides rich features for both compile time and run time error handling. Multi -targeting browsers HTML / JavaScript have different rendering behaviours in different browsers / and their versions. JavaScript have to be written to sublime the differences in browser behaviours. Silverlight works exactly the same in all browsers and works on almost all popular browser. Multi-targeting desktop No support in HTML / JavaScript Silverlight is very close to WPF. Bot the platform may be easily targeted while maintaining the same source code. Rich toolkit HTML /JavaScript have limited toolkit as controls Silverlight provides a rich set of controls including graphs, audio, video, layout, etc. 3. For Architects Design Patterns Silverlight provides for patterns like MVVM (MVC) and rich (fat)  client architecture. This segregates the "separation of concern" very clearly. Client (silverlight) does what it is expected to do and server does what it is expected of. In HTML / JavaScript world most of the processing is done on the server side. Extensibility Silverlight provides great deal of extensibility as custom controls may be made. Extensibility is NOT restricted by browser but by the plug-in silverlight runs in. HTML / JavaScript works in a certain way and extensibility is generally done on the server side rather than client end. Client side is restricted by the limitations of the browser. Performance Silverlight provides localized storage which may be used for cached data storage. this reduces the response time. As processing can be done on client side itself; there is no need for server round trips. this decreases the round about time. Look and feel of the application is downloaded ONLY initially, afterwards ONLY data is fetched form the server. Security Silverlight is compiled code downloaded as .XAP; As compared to HTML / JavaScript, it provides more secure sandboxed approach. Cross - scripting is inherently prohibited in silverlight by default. If proper guidelines are followed silverlight provides much robust security mechanism as against HTML / JavaScript world. For example; knowing server Address in obfuscated JavaScript is easier than a compressed compiled obfuscated silverlight .XAP file. Some of these like (offline and Canvas support) will be available in HTML5. However, the timelines are not encouraging at all. According to Ian Hickson, editor of the HTML5 specification, the specification to reach the W3C Candidate Recommendation stage during 2012, and W3C Recommendation in the year 2022 or later. see http://en.wikipedia.org/wiki/HTML5 for details. The above is MY opinion. I will love to hear yours; do let me know via comments. Technorati Tags: Silverlight

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  • Establishing WebLogic Server HTTPS Trust of IIS Using a Microsoft Local Certificate Authority

    - by user647124
    Everyone agrees that self-signed and demo certificates for SSL and HTTPS should never be used in production and preferred not to be used elsewhere. Most self-signed and demo certificates are provided by vendors with the intention that they are used only to integrate within the same environment. In a vendor’s perfect world all application servers in a given enterprise are from the same vendor, which makes this lack of interoperability in a non-production environment an advantage. For us working in the real world, where not only do we not use a single vendor everywhere but have to make do with self-signed certificates for all but production, testing HTTPS between an IIS ASP.NET service provider and a WebLogic J2EE consumer application can be very frustrating to set up. It was for me, especially having found many blogs and discussion threads where various solutions were described but did not quite work and were all mostly similar but just a little bit different. To save both you and my future (who always seems to forget the hardest-won lessons) all of the pain and suffering, I am recording the steps that finally worked here for reference and sanity. How You Know You Need This The first cold clutches of dread that tells you it is going to be a long day is when you attempt to a WSDL published by IIS in WebLogic over HTTPS and you see the following: <Jul 30, 2012 2:51:31 PM EDT> <Warning> <Security> <BEA-090477> <Certificate chain received from myserver.mydomain.com - 10.555.55.123 was not trusted causing SSL handshake failure.> weblogic.wsee.wsdl.WsdlException: Failed to read wsdl file from url due to -- javax.net.ssl.SSLKeyException: [Security:090477]Certificate chain received from myserver02.mydomain.com - 10.555.55.123 was not trusted causing SSL handshake failure. The above is what started a three day sojourn into searching for a solution. Even people who had solved it before would tell me how they did, and then shrug when I demonstrated that the steps did not end in the success they claimed I would experience. Rather than torture you with the details of everything I did that did not work, here is what finally did work. Export the Certificates from IE First, take the offending WSDL URL and paste it into IE (if you have an internal Microsoft CA, you have IE, even if you don’t use it in favor of some other browser). To state the semi-obvious, if you received the error above there is a certificate configured for the IIS host of the service and the SSL port has been configured properly. Otherwise there would be a different error, usually about the site not found or connection failed. Once the WSDL loads, to the right of the address bar there will be a lock icon. Click the lock and then click View Certificates in the resulting dialog (if you do not have a lock icon but do have a Certificate Error message, see http://support.microsoft.com/kb/931850 for steps to install the certificate then you can continue from the point of finding the lock icon). Figure 1: View Certificates in IE Next, select the Details tab in the resulting dialog Figure 2: Use Certificate Details to Export Certificate Click Copy to File, then Next, then select the Base-64 encoded option for the format Figure 3: Select the Base-64 encoded option for the format For the sake of simplicity, I choose to save this to the root of the WebLogic domain. It will work from anywhere, but later you will need to type in the full path rather than just the certificate name if you save it elsewhere. Figure 4: Browse to Save Location Figure 5: Save the Certificate to the Domain Root for Convenience This is the point where I ran into some confusion. Some articles mentioned exporting the entire chain of certificates. This supposedly works for some types of certificates, or if you have a few other tools and the time to learn them. For the SSL experts out there, they already have these tools, know how to use them well, and should not be wasting their time reading this article meant for folks who just want to get things wired up and back to unit testing and development. For the rest of us, the easiest way to make sure things will work is to just export all the links in the chain individually and let WebLogic Server worry about re-assembling them into a chain (which it does quite nicely). While perhaps not the most elegant solution, the multi-step process is easy to repeat and uses only tools that are immediately available and require no learning curve. So… Next, go to Tools then Internet Options then the Content tab and click Certificates. Go to the Trust Root Certificate Authorities tab and find the certificate root for your Microsoft CA cert (look for the Issuer of the certificate you exported earlier). Figure 6: Trusted Root Certification Authorities Tab Export this one the same way as before, with a different name Figure 7: Use a Unique Name for Each Certificate Repeat this once more for the Intermediate Certificate tab. Import the Certificates to the WebLogic Domain Now, open an command prompt, navigate to [WEBLOGIC_DOMAIN_ROOT]\bin and execute setDomainEnv. You should then be in the root of the domain. If not, CD to the domain root. Assuming you saved the certificate in the domain root, execute the following: keytool -importcert -alias [ALIAS-1] -trustcacerts -file [FULL PATH TO .CER 1] -keystore truststore.jks -storepass [PASSWORD] An example with the variables filled in is: keytool -importcert -alias IIS-1 -trustcacerts -file microsftcert.cer -keystore truststore.jks -storepass password After several lines out output you will be prompted with: Trust this certificate? [no]: The correct answer is ‘yes’ (minus the quotes, of course). You’ll you know you were successful if the response is: Certificate was added to keystore If not, check your typing, as that is generally the source of an error at this point. Repeat this for all three of the certificates you exported, changing the [ALIAS-1] and [FULL PATH TO .CER 1] value each time. For example: keytool -importcert -alias IIS-1 -trustcacerts -file microsftcert.cer -keystore truststore.jks -storepass password keytool -importcert -alias IIS-2 -trustcacerts -file microsftcertRoot.cer -keystore truststore.jks -storepass password keytool -importcert -alias IIS-3 -trustcacerts -file microsftcertIntermediate.cer -keystore truststore.jks -storepass password In the above we created a new JKS key store. You can re-use an existing one by changing the name of the JKS file to one you already have and change the password to the one that matches that JKS file. For the DemoTrust.jks  that is included with WebLogic the password is DemoTrustKeyStorePassPhrase. An example here would be: keytool -importcert -alias IIS-1 -trustcacerts -file microsoft.cer -keystore DemoTrust.jks -storepass DemoTrustKeyStorePassPhrase keytool -importcert -alias IIS-2 -trustcacerts -file microsoftRoot.cer -keystore DemoTrust.jks -storepass DemoTrustKeyStorePassPhrase keytool -importcert -alias IIS-2 -trustcacerts -file microsoftInter.cer -keystore DemoTrust.jks -storepass DemoTrustKeyStorePassPhrase Whichever keystore you use, you can check your work with: keytool -list -keystore truststore.jks -storepass password Where “truststore.jks” and “password” can be replaced appropriately if necessary. The output will look something like this: Figure 8: Output from keytool -list -keystore Update the WebLogic Keystore Configuration If you used an existing keystore rather than creating a new one, you can restart your WebLogic Server and skip the rest of this section. For those of us who created a new one because that is the instructions we found online… Next, we need to tell WebLogic to use the JKS file (truststore.jks) we just created. Log in to the WebLogic Server Administration Console and navigate to Servers > AdminServer > Configuration > Keystores. Scroll down to “Custom Trust Keystore:” and change the value to “truststore.jks” and the value of “Custom Trust Keystore Passphrase:” and “Confirm Custom Trust Keystore Passphrase:” to the password you used when earlier, then save your changes. You will get a nice message similar to the following: Figure 9: To Be Safe, Restart Anyways The “No restarts are necessary” is somewhat of an exaggeration. If you want to be able to use the keystore you may need restart the server(s). To save myself aggravation, I always do. Your mileage may vary. Conclusion That should get you there. If there are some erroneous steps included for your situation in particular, I will offer up a semi-apology as the process described above does not take long at all and if there is one step that could be dropped from it, is still much faster than trying to figure this out from other sources.

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  • Sliding collision response

    - by dbostream
    I have been reading plenty of tutorials about sliding collision responses yet I am not able to implement it properly in my project. What I want to do is make a puck slide along the rounded corner boards of a hockey rink. In my latest attempt the puck does slide along the boards but there are some strange velocity behaviors. First of all the puck slows down a lot pretty much right away and then it slides for awhile and stops before exiting the corner. Even if I double the speed I get a similar behavior and the puck does not make it out of the corner. I used some ideas from this document http://www.peroxide.dk/papers/collision/collision.pdf. This is what I have: Update method called from the game loop when it is time to update the puck (I removed some irrelevant parts). I use two states (current, previous) which are used to interpolate the position during rendering. public override void Update(double fixedTimeStep) { /* Acceleration is set to 0 for now. */ Acceleration.Zero(); PreviousState = CurrentState; _collisionRecursionDepth = 0; CurrentState.Position = SlidingCollision(CurrentState.Position, CurrentState.Velocity * fixedTimeStep + 0.5 * Acceleration * fixedTimeStep * fixedTimeStep); /* Should not this be affected by a sliding collision? and not only the position. */ CurrentState.Velocity = CurrentState.Velocity + Acceleration * fixedTimeStep; Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private Vector2 SlidingCollision(Vector2 position, Vector2 velocity) { if(_collisionRecursionDepth > 5) return position; bool collisionFound = false; Vector2 futurePosition = position + velocity; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ if(!collisionFound) return futurePosition; /* If no collision was detected it is safe to move to the future position. */ /* It is not exactly the intersection point, but slightly before. */ Vector2 newPosition = intersectionPoint; /* oldVelocity is set to the distance from the newPosition(intersection point) to the position it had moved to had it not collided. */ Vector2 oldVelocity = futurePosition - newPosition; /* Project the distance left to move along the intersection normal. */ Vector2 newVelocity = oldVelocity - intersectionPointNormal * oldVelocity.DotProduct(intersectionPointNormal); if(newVelocity.LengthSq() < 0.001) return newPosition; /* If almost no speed, no need to continue. */ _collisionRecursionDepth++; return SlidingCollision(newPosition, newVelocity); } What am I doing wrong with the velocity? I have been staring at this for very long so I have gone blind. I have tried different values of recursion depth but it does not seem to make it better. Let me know if you need more information. I appreciate any help. EDIT: A combination of Patrick Hughes' and teodron's answers solved the velocity problem (I think), thanks a lot! This is the new code: I decided to use a separate recursion method now too since I don't want to recalculate the acceleration in each recursion. public override void Update(double fixedTimeStep) { Acceleration.Zero();// = CalculateAcceleration(fixedTimeStep); PreviousState = new MovingEntityState(CurrentState.Position, CurrentState.Velocity); CurrentState = SlidingCollision(CurrentState, fixedTimeStep); Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private MovingEntityState SlidingCollision(MovingEntityState state, double timeStep) { bool collisionFound = false; /* Calculate the next position given no detected collision. */ Vector2 futurePosition = state.Position + state.Velocity * timeStep; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ /* If no collision was detected it is safe to move to the future position. */ if (!collisionFound) return new MovingEntityState(futurePosition, state.Velocity); /* Set new position to the intersection point (slightly before). */ Vector2 newPosition = intersectionPoint; /* Project the new velocity along the intersection normal. */ Vector2 newVelocity = state.Velocity - 1.90 * intersectionPointNormal * state.Velocity.DotProduct(intersectionPointNormal); /* Calculate the time of collision. */ double timeOfCollision = Math.Sqrt((newPosition - state.Position).LengthSq() / (futurePosition - state.Position).LengthSq()); /* Calculate new time step, remaining time of full step after the collision * current time step. */ double newTimeStep = timeStep * (1 - timeOfCollision); return SlidingCollision(new MovingEntityState(newPosition, newVelocity), newTimeStep); } Even though the code above seems to slide the puck correctly please have a look at it. I have a few questions, if I don't multiply by 1.90 in the newVelocity calculation it doesn't work (I get a stack overflow when the puck enters the corner because the timeStep decreases very slowly - a collision is found early in every recursion), why is that? what does 1.90 really do and why 1.90? Also I have a new problem, the puck does not move parallell to the short side after exiting the curve; to be more exact it moves outside the rink (I am not checking for any collisions with the short side at the moment). When I perform the collision detection I first check that the puck is in the correct quadrant. For example bottom-right corner is quadrant four i.e. circleCenter.X < puck.X && circleCenter.Y puck.Y is this a problem? or should the short side of the rink be the one to make the puck go parallell to it and not the last collision in the corner? EDIT2: This is the code I use for collision detection, maybe it has something to do with the fact that I can't make the puck slide (-1.0) but only reflect (-2.0): /* Point is the current position (not the predicted one) and quadrant is 4 for the bottom-right corner for example. */ if (GeometryHelper.PointInCircleQuadrant(circleCenter, circleRadius, state.Position, quadrant)) { /* The line is: from = state.Position, to = futurePosition. So a collision is detected when from is inside the circle and to is outside. */ if (GeometryHelper.LineCircleIntersection2d(state.Position, futurePosition, circleCenter, circleRadius, intersectionPoint, quadrant)) { collisionFound = true; /* Set the intersection point to slightly before the real intersection point (I read somewhere this was good to do because of floting point precision, not sure exactly how much though). */ intersectionPoint = intersectionPoint - Vector2.NormalizeRet(state.Velocity) * 0.001; /* Normal at the intersection point. */ intersectionPointNormal = Vector2.NormalizeRet(circleCenter - intersectionPoint) } } When I set the intersection point, if I for example use 0.1 instead of 0.001 the puck travels further before it gets stuck, but for all values I have tried (including 0 - the real intersection point) it gets stuck somewhere (but I necessarily not get a stack overflow). Can something in this part be the cause of my problem? I can see why I get the stack overflow when using -1.0 when calculating the new velocity vector; but not how to solve it. I traced the time steps used in the recursion (initial time step is always 1/60 ~ 0.01666): Recursion depth Time step next recursive call [Start recursion, time step ~ 0.016666] 0 0,000985806527246773 [No collision, stop recursion] [Start recursion, time step ~ 0.016666] 0 0,0149596704364629 1 0,0144883449376379 2 0,0143155612984837 3 0,014224925727213 4 0,0141673917461608 5 0,0141265435314026 6 0,0140953966184117 7 0,0140704653746625 ...and so on. As you can see the collision is detected early in every recursive call which means the next time step decreases very slowly thus the recursion depth gets very big - stack overflow.

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  • Self-signed certificates for a known community

    - by costlow
    Recently announced changes scheduled for Java 7 update 51 (January 2014) have established that the default security slider will require code signatures and the Permissions Manifest attribute. Code signatures are a common practice recommended in the industry because they help determine that the code your computer will run is the same code that the publisher created. This post is written to help users that need to use self-signed certificates without involving a public Certificate Authority. The role of self-signed certificates within a known community You may still use self-signed certificates within a known community. The difference between self-signed and purchased-from-CA is that your users must import your self-signed certificate to indicate that it is valid, whereas Certificate Authorities are already trusted by default. This works for known communities where people will trust that my certificate is mine, but does not scale widely where I cannot actually contact or know the systems that will need to trust my certificate. Public Certificate Authorities are widely trusted already because they abide by many different requirements and frequent checks. An example would be students in a university class sharing their public certificates on a mailing list or web page, employees publishing on the intranet, or a system administrator rolling certificates out to end-users. Managed machines help this because you can automate the rollout, but they are not required -- the major point simply that people will trust and import your certificate. How to distribute self-signed certificates for a known community There are several steps required to distribute a self-signed certificate to users so that they will properly trust it. These steps are: Creating a public/private key pair for signing. Exporting your public certificate for others Importing your certificate onto machines that should trust you Verify work on a different machine Creating a public/private key pair for signing Having a public/private key pair will give you the ability both to sign items yourself and issue a Certificate Signing Request (CSR) to a certificate authority. Create your public/private key pair by following the instructions for creating key pairs.Every Certificate Authority that I looked at provided similar instructions, but for the sake of cohesiveness I will include the commands that I used here: Generate the key pair.keytool -genkeypair -alias erikcostlow -keyalg EC -keysize 571 -validity 730 -keystore javakeystore_keepsecret.jks Provide a good password for this file. The alias "erikcostlow" is my name and therefore easy to remember. Substitute your name of something like "mykey." The sigalg of EC (Elliptical Curve) and keysize of 571 will give your key a good strong lifetime. All keys are set to expire. Two years or 730 days is a reasonable compromise between not-long-enough and too-long. Most public Certificate Authorities will sign something for one to five years. You will be placing your keys in javakeystore_keepsecret.jks -- this file will contain private keys and therefore should not be shared. If someone else gets these private keys, they can impersonate your signature. Please be cautious about automated cloud backup systems and private key stores. Answer all the questions. It is important to provide good answers because you will stick with them for the "-validity" days that you specified above.What is your first and last name?  [Unknown]:  First LastWhat is the name of your organizational unit?  [Unknown]:  Line of BusinessWhat is the name of your organization?  [Unknown]:  MyCompanyWhat is the name of your City or Locality?  [Unknown]:  City NameWhat is the name of your State or Province?  [Unknown]:  CAWhat is the two-letter country code for this unit?  [Unknown]:  USIs CN=First Last, OU=Line of Business, O=MyCompany, L=City, ST=CA, C=US correct?  [no]:  yesEnter key password for <erikcostlow>        (RETURN if same as keystore password): Verify your work:keytool -list -keystore javakeystore_keepsecret.jksYou should see your new key pair. Exporting your public certificate for others Public Key Infrastructure relies on two simple concepts: the public key may be made public and the private key must be private. By exporting your public certificate, you are able to share it with others who can then import the certificate to trust you. keytool -exportcert -keystore javakeystore_keepsecret.jks -alias erikcostlow -file erikcostlow.cer To verify this, you can open the .cer file by double-clicking it on most operating systems. It should show the information that you entered during the creation prompts. This is the file that you will share with others. They will use this certificate to prove that artifacts signed by this certificate came from you. If you do not manage machines directly, place the certificate file on an area that people within the known community should trust, such as an intranet page. Import the certificate onto machines that should trust you In order to trust the certificate, people within your known network must import your certificate into their keystores. The first step is to verify that the certificate is actually yours, which can be done through any band: email, phone, in-person, etc. Known networks can usually do this Determine the right keystore: For an individual user looking to trust another, the correct file is within that user’s directory.e.g. USER_HOME\AppData\LocalLow\Sun\Java\Deployment\security\trusted.certs For system-wide installations, Java’s Certificate Authorities are in JAVA_HOMEe.g. C:\Program Files\Java\jre8\lib\security\cacerts File paths for Mac and Linux are included in the link above. Follow the instructions to import the certificate into the keystore. keytool -importcert -keystore THEKEYSTOREFROMABOVE -alias erikcostlow -file erikcostlow.cer In this case, I am still using my name for the alias because it’s easy for me to remember. You may also use an alias of your company name. Scaling distribution of the import The easiest way to apply your certificate across many machines is to just push the .certs or cacerts file onto them. When doing this, watch out for any changes that people would have made to this file on their machines. Trusted.certs: When publishing into user directories, your file will overwrite any keys that the user has added since last update. CACerts: It is best to re-run the import command with each installation rather than just overwriting the file. If you just keep the same cacerts file between upgrades, you will overwrite any CAs that have been added or removed. By re-importing, you stay up to date with changes. Verify work on a different machine Verification is a way of checking on the client machine to ensure that it properly trusts signed artifacts after you have added your signing certificate. Many people have started using deployment rule sets. You can validate the deployment rule set by: Create and sign the deployment rule set on the computer that holds the private key. Copy the deployment rule set on to the different machine where you have imported the signing certificate. Verify that the Java Control Panel’s security tab shows your deployment rule set. Verifying an individual JAR file or multiple JAR files You can test a certificate chain by using the jarsigner command. jarsigner -verify filename.jar If the output does not say "jar verified" then run the following command to see why: jarsigner -verify -verbose -certs filename.jar Check the output for the term “CertPath not validated.”

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  • Neo4J and Azure and VS2012 and Windows 8

    - by Chris Skardon
    Now, I know that this has been written about, but both of the main places (http://www.richard-banks.org/2011/02/running-neo4j-on-azure.html and http://blog.neo4j.org/2011/02/announcing-neo4j-on-windows-azure.html) utilise VS2010, and well, I’m on VS2012 and Windows 8. Not that I think Win 8 had anything to do with it really, anyhews! I’m going to begin from the beginning, this is my first foray into running something on Azure, so it’s been a bit of a learning curve. But luckily the Neo4J guys have got us started, so let’s download the VS2010 solution: http://neo4j.org/get?file=Neo4j.Azure.Server.zip OK, the other thing we’ll need is the VS2012 Azure SDK, so let’s get that as well: http://www.windowsazure.com/en-us/develop/downloads/ (I just did the full install). Now, unzip the VS2010 solution and let’s open it in VS2012: <your location>\Neo4j.Azure.Server\Neo4j.Azure.Server.sln One-way-upgrade? Yer! Ignore the migration report – we don’t care! Let’s build that sucker… Ahhh 14 errors… WindowsAzure does not exist in the namespace ‘Microsoft’ Not a problem right? We’ve installed the SDK, just need to update the references: We can ignore the Test projects, they don’t use Azure, we’re interested in the other projects, so what we’ll do is remove the broken references, and add the correct ones, so expand the references bit of each project: hunt out those yellow exclamation marks, and delete them! You’ll need to add the right ones back in (listed below), when you go to the ‘Add Reference’ dialog make sure you have ‘Assemblies’ and ‘Framework’ selected before you seach (and search for ‘microsoft.win’ to narrow it down) So the references you need for each project are: CollectDiagnosticsData Microsoft.WindowsAzure.Diagnostics Microsoft.WindowsAzure.StorageClient Diversify.WindowsAzure.ServiceRuntime Microsoft.WindowsAzure.CloudDrive Microsoft.WindowsAzure.ServiceRuntime Microsoft.WindowsAzure.StorageClient Right, so let’s build again… Sweet! No errors.   Now we need to setup our Blobs, I’m assuming you are using the most up-to-date Java you happened to have downloaded :) in my case that’s JRE7, and that is located in: C:\Program Files (x86)\Java\jre7 So, zip up that folder into whatever you want to call it, I went with jre7.zip, and stuck it in a temp folder for now. In that same temp folder I also copied the neo4j zip I was using: neo4j-community-1.7.2-windows.zip OK, now, we need to get these into our Blob storage, this is where a lot of stuff becomes unstuck - I didn’t find any applications that helped me use the blob storage, one would crash (because my internet speed is so slow) and the other just didn’t work – sure it looked like it had worked, but when push came to shove it didn’t. So this is how I got my files into Blob (local first): 1. Run the ‘Storage Emulator’ (just search for that in the start menu) 2. That takes a little while to start up so fire up another instance of Visual Studio in the mean time, and create a new Console Application. 3. Manage Nuget Packages for that solution and add ‘Windows Azure Storage’ Now you’re set up to add the code: public static void Main() { CloudStorageAccount cloudStorageAccount = CloudStorageAccount.DevelopmentStorageAccount; CloudBlobClient client = cloudStorageAccount.CreateCloudBlobClient(); client.Timeout = TimeSpan.FromMinutes(30); CloudBlobContainer container = client.GetContainerReference("neo4j"); //This will create it as well   UploadBlob(container, "jre7.zip", "c:\\temp\\jre7.zip"); UploadBlob(container, "neo4j-community-1.7.2-windows.zip", "c:\\temp\\neo4j-community-1.7.2-windows.zip"); }   private static void UploadBlob(CloudBlobContainer container, string blobName, string filename) { CloudBlob blob = container.GetBlobReference(blobName);   using (FileStream fileStream = File.OpenRead(filename)) blob.UploadFromStream(fileStream); } This will upload the files to your local storage account (to switch to an Azure one, you’ll need to create a storage account, and use those credentials when you make your CloudStorageAccount above) To test you’ve got them uploaded correctly, go to: http://localhost:10000/devstoreaccount1/neo4j/jre7.zip and you will hopefully download the zip file you just uploaded. Now that those files are there, we are ready for some final configuration… Right click on the Neo4jServerHost role in the Neo4j.Azure.Server cloud project: Click on the ‘Settings’ tab and we’ll need to do some changes – by default, the 1.7.2 edition of neo4J unzips to: neo4j-community-1.7.2 So, we need to update all the ‘neo4j-1.3.M02’ directories to be ‘neo4j-community-1.7.2’, we also need to update the Java runtime location, so we start with this: and end with this: Now, I also changed the Endpoints settings, to be HTTP (from TCP) and to have a port of 7410 (mainly because that’s straight down on the numpad) The last ‘gotcha’ is some hard coded consts, which had me looking for ages, they are in the ‘ConfigSettings’ class of the ‘Neo4jServerHost’ project, and the ones we’re interested in are: Neo4jFileName JavaZipFileName Change those both to what that should be. OK Nearly there (I promise)! Run the ‘Compute Emulator’ (same deal with the Start menu), in your system tray you should have an Azure icon, when the compute emulator is up and running, right click on the icon and select ‘Show Compute Emulator UI’ The last steps! Make sure the ‘Neo4j.Azure.Server’ cloud project is set up as the start project and let’s hit F5 tension mounts, the build takes place (you need to accept the UAC warning) and VS does it’s stuff. If you look at the Compute Emulator UI you’ll see some log stuff (which you’ll need if this goes awry – but it won’t don’t worry!) In a bit, the console and a Java window will pop up: Then the console will bog off, leaving just the Java one, and if we switch back to the Compute Emulator UI and scroll up we should be able to see a line telling us the port number we’ve been assigned (in my case 7411): (If you can’t see it, don’t worry.. press CTRL+A on the emulator, then CTRL+C, copy all the text and paste it into something like Notepad, then just do a Find for ‘port’ you’ll soon see it) Go to your favourite browser, and head to: http://localhost:YOURPORT/ and you should see the WebAdmin! See you on the cloud side hopefully! Chris PS Other gotchas! OK, I’ve been caught out a couple of times: I had an instance of Neo4J running as a service on my machine, the Azure instance wanted to run the https version of the server on the same port as the Service was running on, and so Java would complain that the port was already in use.. The first time I converted the project, it didn’t update the version of the Azure library to load, in the App.Config of the Neo4jServerHost project, and VS would throw an exception saying it couldn’t find the Azure dll version 1.0.0.0.

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