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• Spring 2.0.0/2.0.6 to 3.0.5 migration stories

  - by Pangea

  We are in the process of migrating to 3.0.5 of spring from 2.0.x. We mainly use spring in below scenarios custom scope: thread local scope persistence: jdbc+hibernate 3.6 (but moving to mix of ejb 3.0+jpa 2.0+hibernate, not sure if all 3 can co-exist in 1 app) transactions: local (but planning to use jta due to the necessity of using multiple persistence inits, and has to use ejb+jpa+hibernate in 1 single trans), declarative trans mgmt parent-child contexts cxf annotations+xml OracleLobHandler Resource/ResourceBundleMessageResource JSF/Facelets with FacesSpringVariableResolver ActiveMQ integration Quartz integration TaskExecutor JMX exporter HttpExporter/Invoker Appreciate if someone can share their experiences like what to watch out for head aches/pain points which ones to drop for better alternate choices in new 3.0.5 release Is it better to switch from commons/iscreen validator to Hibernate Validator (Spec impl) or Spring Validator Is there a bean mapping framework in spring that i can use instead of Dozer XSLT transformation helper: currently we have small homegrown framework to cache xslts during load. if spring can do that for me then I would like to drop this Encryption/Decryption support. Password generation support. Authentication with SALT any SAML (or claims based secur New ideas Suggestions Switch to latest version of aspectj Upgrade guide from 2.5 to 3.0.5

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• Favourite Features of VS 2010

  - by Noldorin

  With the general public release of Visual Studio 2010 Beta 2 today, this latest version has created a lot of hype and interest. Indeed, the opinion I've gauged is that VS 2010 has resolved a great deal of the minor flaws left over from previous versions, as well as added some particularly useful new code editor and project development tools (in particular the Premium/Ultimate versions). My question here is: what are you favourite new features in VS 2010 that have really got you excited? Or similarly, what are the flaws of VS 2008 that you are most glad to have resolved? There is a wealth of changes in VS 2010, of course, but these are some of the ones that have interested me most (about which I know!). Integrated support for F# (with multi-targeting for .NET 2.0 - 4.0)/ Much improved WPF designer. The VS 2008 was more than a bit buggy at times. Great improvements to the code editor, such as call hierarchy viewing. A decent add-in framework. A greatly expanded testing framework (now capable of database testing, for example) in Premium/Ultimate. Project planning and modelling features in Premium/Ultimate. If I could request one point/feature per post, I think that would be best, so we could vote them individually.

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• mvn deploy to AWS (ssh via distributionManagement)

  - by Dexter

  I am working on deploying the WAR file to AWS using Maven. I am planning to use 'mvn deploy' for the same which would ssh the war file to AWS. I am following http://maven.apache.org/plugins/maven-deploy-plugin/examples/deploy-ssh-external.html. This is my POM file <project> ... <distributionManagement> <repository> <id>ssh-aws</id> <url>scpexe://<ec2 instance>.compute-1.amazonaws.com</url> </repository> </distributionManagement> <build> <extensions> <!-- Enabling the use of FTP --> <extension> <groupId>org.apache.maven.wagon</groupId> <artifactId>wagon-ssh-external</artifactId> <version>1.0-beta-6</version> </extension> </extensions> </build> .. </project> This is my settings.xml <server> <id>ssh-aws</id> <username>aws-user</username> </server> The only issue is that I am unable to figure out the url in distributionManagement node of pom.xml. I am able to ssh in the AWS server by the following. ssh -i ~/pemfile/pemfile-key.pem aws-user@<ec2 instance>.compute-1.amazonaws.com But when I run mvn clean deploy, I receive this.. Exit code: 1 - Permission denied (publickey). -> [Help 1] Thanks in advance.

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• visualising piano performance evaluation

  - by Dolphin

  I need to develop a performance evaluator for piano playing. Based on a midi generated from sheet music, I need to evaluate the midi of the actual playing (midi keyboard). I'm planning to evaluate the playing based on note pitch, duration and loudness. The evaluation is I suppose a comparison of the notes of the sheet music and playing in midi. But I have no idea how I can visualise (i.e. show where the person have gone wrong) this evaluation process. i.e. maybe show both the notation and highlight which note has gone wrong. But how can I show any of this in some graphical form? Or more precisely on a stave (a music score) itself. I have note details (pitch, duration) and score details (key and time signature) stored in a table, and I'm using Java. But I have no clue as in how I can put all this into graphical form. Any insight is most gratefully appreciated. Advance thanks

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• Tools\addin's for formating or cleaning up xaml?

  - by cody

  I'm guessing these don't exist since I searched around for these but I'm looking for a few tools: 1) A tool that cleans up my xaml so that the properties of elements are consistent through a file. I think enforcing that consistence would make the xaml easier to read. Maybe there could be a hierarchy of what comes first but if not alphabetical might work. Example before: TextBox Name="myTextBox1" Grid.Row="3" Grid.Column="1" Margin="4" TextBox Grid.Column="1" Margin="4" Name="t2" Grid.Row="3" Example after: TextBox Name="myTextBox1" Grid.Row="3" Grid.Column="1" Margin="4" TextBox Name="t2" Grid.Row="3" Grid.Column="1" Margin="4" (note < / has been remove from the above since control seem to have issues parsing whe the after section was added) 2) Along the same lines as above, to increase readability, a tool to align properties, so from the above code example similar props would start in the same place. <TextBox Name="myTextBox1" Grid.Row="3" Grid.Column="1" Margin="4"/> <TextBox Name="t2" Grid.Row="3" Grid.Column="1" Margin="4"/> I know VS has default settings for XAML documents so props can be on one line or separate lines so maybe if there was a tool as described in (1) this would not be needed...but it would still be nice if you like your props all on one line. 3) A tool that adds X to the any of the Grid.Row values and Y to any of the Grid.Column values in the selected text. Every time I add a new row\column I have to go manually fix these. From my understanding Expression Blend can help with this but seem excessive to open Blend just to increment some numbers (and just don't grok Blend). Maybe vs2010 with the designer will help but right now I'm on VS08 and Silverlight. Any one know of any tools to help with this? Anyone planning to write something like this...I'm looking at you JetBrains and\or DevExpress. Thanks.

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• Fast, easy, and secure method to perform DB actions with GET

  - by rob - not a robber

  Hey All, Sort of a methods/best practices question here that I am sure has been addressed, yet I can't find a solution based on the vague search terms I enter. I know starting off the question with "Fast and easy" will probably draw out a few sighs, so my apologies. Here is the deal. I have a logged in area where an ADMIN can do a whole host of POST operations to input data relating to their profile. The way I have data structured is pretty distinct and well segmented in most tables as it relates to the ID of the admin. Now, I have a table where I dump one type of data into and differentiate this data by assigning the ADMIN's unique ID to each record. In other words, all ADMINs have this one type of data writing to this table. I just differentiate by the ADMIN ID with each record. I was planning on letting the ADMIN remove these records by clicking on a link with a query string - obviously using GET. Obviously, the query structure is in the link so any logged in admin could then exploit the URL and delete a competitor's records. Is the only way to safely do this through POST or should I pass through the session info that includes password and validate it against the ADMIN ID that is requesting the delete? This is obviously much more work for me. As they said in the auto repair biz I used to work in... there are 3 ways to do a job: Fast, Good, and Cheap. You can only have two at a time. Fast and cheap will not be good. Good and cheap will not have fast turnaround. Fast and good will NOT be cheap. haha I guess that applies here... can never have Fast, Easy and Secure all at once ;) Thanks in advance...

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• Show users a list of unique items on Java Google App Engine

  - by James

  I've been going round in circles with what must be a very simple challenge but I want to do it the most efficient way from the start. So, I've watched Brett Slatkin's Google IO videos (2008 & 2009) about building scalable apps including http://www.youtube.com/watch?v=AgaL6NGpkB8 and read the docs but as a n00b, I'm still not sure. I'm trying to build an app on GAEJ similar to the original 'hotornot' where a user is presented with an item which they rate. Once they rate it, they are presented with another one which they haven't seen before. My question is this; is it most efficient to do a query up front to grab x items (say 100) and put them in a list (stored in memcache?) or is it better to simply make a query for a new item after each rating. To keep track of the items a user has seen, I'm planning to keep those items' keys in a list property of the user's entity. Does that sound sensible? I've really got myself confused about this so any help would be much appreciated.

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• Good tools for keeping the content in test/staging/live environments synchronized

  - by David Stratton

  I'm looking for recommendations on automated folder synchronization tools to keep the content in our three environments synchronized automatically. Specifically, we have several applications where a user can upload content (via a File Upload page or a similar mechanism), such as images, pdf files, word documents, etc. In the past, we had the user doing this to our live server, and as a result, our test and staging servers had to be manually synchronized. Going forward, we will have them upload content to the staging server, and we would like some software to automatically copy the files off to the test and live servers EITHER on a scheduled basis OR as the files get uploaded. I was planning on writing my own component, and either set it up as a scheduled task, or use a FileSystemWatcher, but it occurred to me that this has probably already been done, and I might be better off with some sort of synchronization tool that already exists. On our web site, there are a limited number of folders that we want to keep synchronized. In these folders, it is an all or nothing - we want to make sure the folders are EXACT duplicates. This should make it fairly straightforward, and I would think that any software that can synchronize folders would be OK, except that we also would like the software to log changes. (This rules out simple BATCH files.) So I'm curious, if you have a similar environment, how did you solve the challenge of keeping everything synchronized. Are you aware of a tool that is reliable, and will meet our needs? If not, do you have a recommendation for something that will come close, or better yet, an open source solution where we can get the code and modify it as needed? (preferably .NET). Added Also, I DID google this first, but there are so many options, I am interested mostly in knowing what actually works well vs what they SAY works, which is why I'm asking here.

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• Record the timestamps of slide changes during a live Powerpoint presentation?

  - by StackedCrooked

  I am planning to implement a lecture capture solution. One of the requirements is to record both the presenter and the slideshow. The presenter is recorded with a videocamera obviously, and the slideshow will probably be captured using a tool like Camtasia. Now during playback three components are visible: the presenter, the slides and a table of contents. Clicking a chapter title in the TOC causes the video to navigate to the corresponding section. This means that a mapping must be made between chapter titles and their timestamps in the video. Usually a change of topic is accompanied with a slide change in the Powerpoint presentation. So the timestamps could be deduced from the slidechanges. However, this requires me to detect slide changes during the live presentation. And I don't know how to do that. Anyone here knows how to do detect slide changes? Is there a Powerpoint API where I can connect event handlers or something like that? I'd greatly appreciate your help! Edit This issue is no longer relevant for my current work so this question will not be updated by me. However, you are still free to help others by posting your answers/insights here.

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• Thread Safety of C# List<T> for readers

  - by ILIA BROUDNO

  I am planning to create the list once in a static constructor and then have multiple instances of that class read it (and enumerate through it) concurrently without doing any locking. In this article http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx MS describes the issue of thread safety as follows: Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe. A List can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. The "Enumerating through a collection is intrinsically not a thread-safe procedure." Statement is what worries me. Does this mean that it is thread safe for readers only scenario, but as long as you do not use enumeration? Or is it safe for my scenario?

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• problem adding object to hashtable

  - by daemonkid

  I am trying to call a class method dynamically depending on a condition. This is how I am doing it I have three classes implement a single interface interface IReadFile { string DoStuff(); } The three classes A,B,C implement the interface above. I am trying to add them to a hashtable with the code below _HashT.Add("a", new classA()); _HashT.Add("b", new classB()); _HashT.Add("c", new classC()); This compiles fine, but gives a runtime error.{Object reference not set to an instance of an object.} I was planning to return the correct class to the interface type depending on a parameter that matches the key value. say if I send in a. ClassA is returned to the interface type and the method is called. IReadFile Obj = (IReadFile )_HashT["a"].GetType(); obj.DoStuff(); How do I correct the part above where the objects need to be added to the hashtable? Or do I need to use a different approach? All the classes are in the same assembly and namespace. Thanks for your time.

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• maven assemblies. Putting each dependency with transitive dependencies in own directory?

  - by jr

  I have a maven project which consists of a few modules. This is to be deployed on a client machine and will involve installing Tomcat and will make use of NSIS for installer. There is a separate application which monitors tomcat and can restart it, perform updates, etc. So, I have the modules setup as follows: project +-- client (all code, handlers, for the war) +-- client-common - (shared code, shared between monitor and client) +-- client-web - (the war, basically just uses war has applicationcontext, web.xml,etc) +-- monitor - (the monitor application jar. Uses wrapper to run) So, I need to create an installer. I was planning on creating another module which would be the installer. This is where I would have tomcat directory and I'd like maven to "assemble" everything and then run NSIS so I can create the final installer. However, I need to have the monitor jar file in a directory and then have all monitors dependencies in a lib/ directory. The final directory structure should be: project-installer-directory/monitor/monitor-version.jar project-installer-directory/monitor/lib/monitor-dep-1.jar project-installer-directory/monitor/lib/monitor-dep-2.jar project-installer-directory/monitor/lib/monitor-dep-3.jar project-installer-directory/webapps/client-web.war Where in the client-web\WEB-INF\lib directory we will have all client-web's dependencies after it is exploded. That works, I have the .war file. What I am having problems with is getting the monitor module dependencies independent of the dependencies of the client-web module. I tried to just create the installer module and make the monitor and client-web dependencies, but when I use dependencies-copy it gives me everything. Not what I want. I'm leaning towards creating a new module called monitor-assembly or something to give me a zip file which contains the directory format I need, but that is yet another module. Can someone please help me with the correct way to accomplish this? thanks!

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• Protecting Content with AuthLogic

  - by Rob Wilkerson

  I know this sounds like a really, really simple use case and I'm hoping that it is, but I swear I've looked all over the place and haven't found any mention of any way - not even the best way - of doing this. I'm brand-spanking new to Ruby, Rails and everything surrounding either (which may explain a lot). The dummy app that I'm using as my learning tool requires authentication in order to do almost anything meaningful, so I chose to start by solving that problem. I've installed the AuthLogic gem and have it working nicely to the extent that is covered by the intro documentation and Railscast, but now that I can register, login and logout...I need to do something with it. As an example, I need to create a page where users can upload images. I'm planning to have an ImagesController with an upload action method, but I want that only accessible to logged in users. I suppose that in every restricted action I could add code to redirect if there's no current_user, but that seems really verbose. Is there a better way of doing this that allows me to define or identify restricted areas and handle the authentication check in one place?

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• What are the advantages of using J2EE over ASP.net?

  - by m_oLogin

  We are currently planning to launch a couple of internal web projects in the future. Our company's dev teams are mostly experienced in J2EE and have worked with it for years. Today, we have the choice of launching a couple of our projects on .net. I have checked out a couple of sources on the net, and it seems like the "J2EE vs ASP.net" combat brings out as much discord as the overseen "Apple vs Microsoft" or "Free Eclipse vs Visual Studio"... Nevertheless, I have been somewhat quite impressed with ASP.net's abilities to create great things with huge simplicity (for ex. asp.net ajax's demos). No more tons of xmls to play with, no more tons of frameworks to configure (we usually use the famous combo struts/spring/hibernate)... It just seemed to me that ASP.net had some good advantages over J2EE, but then again, I may speak by ignorance. What I want to know is this : What are the real advantages of using J2EE over ASP.net? Is there anything that cannot be done in ASP.net that can be done in J2EE? Once the frameworks are all in place and configured, is it faster to develop apps in J2EE than it is in .net? Are the applications generally easier to maintain in J2EE than in ASP.net? Is it worth it for some developpers to leave their J2EE knowledge on the side and move on to ASP.net if it does exactly the same thing?

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• Sprint velocity calculations

  - by jase

  Need some advice on working out the team velocity for a sprint. Our team normally consists of about 4 developers and 2 testers. The scrum master insists that every team member should contribute equally to the velocity calculation i.e. we should not distinguish between developers and testers when working out how much we can do in a sprint. The is correct according to Scrum, but here's the problem. Despite suggestions to the contrary, testers never help with non-test tasks and developers never help with non-dev tasks, so we are not cross functional team members at all. Also, despite various suggestions, testers normally spend the first few days of each sprint waiting for something to test. The end result is that typically we take on far more dev work than we actually have capacity for in the sprint. For example, the developers might contribute 20 days to the velocity calculation and the testers 10 days. If you add up the tasks after sprint planning though, dev tasks add up to 25 days and test tasks add up to 5 days. How do you guys deal with this sort of situation?

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• Script to install and compile Python, Django, Virtualenv, Mercurial, Git, LessCSS, etc... on Dreamho

  - by tmslnz

  The Story After cleaning up my Dreamhost shared server's home folder from all the cruft accumulated over time, I decided to start afresh and compile/reinstall Python. All tutorials and snippets I found seemed overly simplistic, assuming (or ignoring) a bunch of dependencies needed by Python to compile all modules correctly. So, starting from http://andrew.io/weblog/2010/02/installing-python-2-6-virtualenv-and-virtualenvwrapper-on-dreamhost/ (so far the best guide I found), I decided to write a set-and-forget Bash script to automate this painful process, including along the way a bunch of other things I am planning to use. The Script I am hosting the script on http://bitbucket.org/tmslnz/python-dreamhost-batch/src/ The TODOs So far it runs fine, and does all it needs to do in about 900 seconds, giving me at the end of the process a fully functional Python / Mercurial / etc... setup without even needing to log out and back in. I though this might be of use for others too, but there are a few things that I think it's missing and I am not quite sure how to go for it, what's the best way to do it, or if this just doesn't make any sense at all. Check for errors and break Check for minor version bumps of the packages and give warnings Check for known dependencies Use arguments to install only some of the packages instead of commenting out lines Organise the code in a manner that's easy to update Optionally make the installers and compiling silent, with error logging to file failproof .bashrc modification to prevent breaking ssh logins and having to log back via FTP to fix it EDIT: The implied question is: can anyone, more bashful than me, offer general advice on the worthiness of the above points or highlight any problems they see with this approach? (see my answer to Ry4an's comment below) The Gist I am no UNIX or Bash or compiler expert, and this has been built iteratively, by trial and error. It is somehow going towards apt-get (well, 1% of it...), but since Dreamhost and others obviously cannot give root access on shared servers, this looks to me like a potentially very useful workaround; particularly so with some community work involved.

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• How to properly set relationships in Core Data when using setValue and data already exists

  - by ern

  Let's say I have two objects: Articles and Categories. For the sake of this example all relevant categories have already been added to the data store. When looping through data that holds edits for articles, there is category relationship information that needs to be saved. I was planning on using the -setValue method in the Article class in order to set the relationships like so: - (void)setValue:(id)value forUndefinedKey:(NSString *)key { if([key isEqualToString:@"categories"]){ NSLog(@"trying to set categories..."); } } The problem is that value isn't a Category, it is just a string (or array of strings) holding the title of a category. I could certainly do a lookup within this method for each category and assign it, but that seems inefficient when processing a whole bunch of articles at once. Another option is to populate an array of all possible categories and just filter, but my question is where to store that array? Should it be a class method on Article? Is there a way to pass in additional data to the -setValue method? Is there another, better option for setting the relationship I'm not thinking of? Thanks for your help.

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• Appropriate Footwear for An Interview

  - by EoRaptor013

  There's a raging debate going on at my house about appropriate footwear for an IT interview. I have an interview, on Thursday, for a SQL/C# developer with the Fraud dept. at a large accounting firm. I was planning on wearing what I have pretty much always worn for an interview: a nice suit, white shirt, subdued tie, and a pair of dress cowboy boots. My spouse and daughter both know that my dress code for nearly every professional job I've ever gotten, is pretty much the same -- including the boots -- with what I just described. Now, however, because I've been out of work for an unfortunately long time (my last contract ended 03/09 -- pretty much coincidental with the bottom falling out of the economy). My wife insists that style standards are fundamentally different on the left side of the Mississippi vs. the right side of the river. My view is that I've always worn "cowboy" boots; since I was old enough to fit into a real pair. I moved East, as an adult, over 30 years ago, but my dress patterns haven't changed. And in all that time, my dress patterns have never changed. Now I both really want, and really need, this job. But, is that sufficient reason to change a habit 40 years in the making? I would really appreciate the thoughts ya'all (little West of Ms. colloquialism, there) might have on this matter. Thanks. P.S. If this sort of question is inappropriate for this form, I apologize.

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• Should I return IEnumerable<T> or IQueryable<T> from my DAL?

  - by Gary '-'

  I know this could be opinion, but I'm looking for best practices. As I understand, IQueryable implements IEnumerable, so in my DAL, I currently have method signatures like the following: IEnumerable<Product> GetProducts(); IEnumerable<Product> GetProductsByCategory(int cateogoryId); Product GetProduct(int productId); Should I be using IQueryable here? What are the pros and cons of either approach? Note that I am planning on using the Repository pattern so I will have a class like so: public class ProductRepository { DBDataContext db = new DBDataContext(<!-- connection string -->); public IEnumerable<Product> GetProductsNew(int daysOld) { return db.GetProducts() .Where(p => p.AddedDateTime > DateTime.Now.AddDays(-daysOld )); } } Should I change my IEnumerable<T> to IQueryable<T>? What advantages/disadvantages are there to one or the other?

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• How do I programatically verify, create, and update SQL table structure?

  - by JYelton

  Scenario: I have an application (C#) that expects a SQL database and login, which are set by a user. Once connected, it checks for the existence of several table and creates them if not found. I'd like to expand on this by having the program be capable of adding columns to those tables if I release a new version of the program which relies upon the new columns. Question: What is the best way to programatically check the structure of an existing SQL table and create or update it to match an expected structure? I am planning to iterate through the list of required columns and alter the existing table whenever it does not contain the new column. I can't help but wonder if there's an approach that is different or better. Criteria: Here are some of my expectations and self-imposed rules: Newer versions of the program might no longer use certain columns, but they would be retained for data logging purposes. In other words, no columns will be removed. Existing data in the table must be preserved, so the table cannot simply be dropped and recreated. In all cases, newly added columns would allow null data, so the population of old records is taken care of by having default null values. Example: Here is a sample table (because visual examples help!): id sensor_name sensor_status x1 x2 x3 x4 1 na019 OK 0.01 0.21 1.41 1.22 Then, in a new version, I may want to add the column x5. The "x-columns" are all data-storage columns that accept null.

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• Is ADO.NET Entity framework database schema update possible?

  - by fyasar

  I'm working on proof of concept application like crm and i need your some advice. My application's data layer completely dynamic and run onto EF 3.5. When the user update the entity, change relation or add new column to the database, first i'm planning make for these with custom classes. After I rebuild my database model layer with new changes during the application runtime. And my model layer tie with tightly coupled to my project for easy reflecting model layer changes (It connected to my project via interfaces and loading onto to application domain in the runtime). I need to create dynamic entities, create entity relations and modify them during the runtime after that i need to create change database script for updating database schema. I know ADO.NET team says "we will be able to provide this property in EF 4.0", but i don't need to wait for them. How can i update database changes during the runtime via EF 3.5 ? For example, i need to create new entity or need to change some entity schema, add new properties or change property types after than how can apply these changes on the physical database schema ? Any ideas ?

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• How to read time from recorded surveillance camera video?

  - by stressed_geek

  I have a problem where I have to read the time of recording from the video recorded by a surveillance camera. The time shows up on the top-left area of the video. Below is a link to screen grab of the area which shows the time. Also, the digit color(white/black) keeps changing during the duration of the video. http://i55.tinypic.com/2j5gca8.png Please guide me in the direction to approach this problem. I am a Java programmer so would prefer an approach through Java. EDIT: Thanks unhillbilly for the comment. I had looked at the Ron Cemer OCR library and its performance is much below our requirement. Since the ocr performance is less than desired, I was planning to build a character set using the screen grabs for all the digits, and using some image/pixel comparison library to compare the frame time with the character-set which will show a probabilistic result after comparison. So I was looking for a good image comparison library(I would be OK with a non-java library which I can run using the command-line). Also any advice on the above approach would be really helpful.

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• Interchange structured data between Haskell and C

  - by Eonil

  First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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• Improve Log Exceptions

  - by Jaider

  I am planning to use log4net in a new web project. In my experience, I see how big the log table can get, also I notice that errors or exceptions are repeated. For instance, I just query a log table that have more than 132.000 records, and I using distinct and found that only 2.500 records are unique (~2%), the others (~98%) are just duplicates. so, I came up with this idea to improve logging. Having a couple of new columns: counter and updated_dt, that are updated every time try to insert same record. If want to track the user that cause the exception, need to create a user_log or log_user table, to map N-N relationship. Create this model may made the system slow and inefficient trying to compare all these long text... Here the trick, we should also has a hash column of binary of 16 or 32, that hash the message and the exception, and configure an index on it. We can use HASHBYTES to help us. I am not an expert in DB, but I think that will made the faster way to locate a similar record. And because hashing doesn't guarantee uniqueness, will help to locale those similar record much faster and later compare by message or exception directly to make sure that are unique. This is a theoretical/practical solution, but will it work or bring more complexity? what aspects I am leaving out or what other considerations need to have? the trigger will do the job of insert or update, but is the trigger the best way to do it?

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• How can I cluster short messages [Tweets] based on topic ? [Topic Based Clustering]

  - by Jagira

  Hello, I am planning an application which will make clusters of short messages/tweets based on topics. The number of topics will be limited like Sports [ NBA, NFL, Cricket, Soccer ], Entertainment [ movies, music ] and so on... I can think of two approaches to this Ask for users to tag questions like Stackoverflow does. Users can select tags from a predefined list of tags. Then on server side I will cluster them on based of tags. Pros:- Simple design. Less complexity in code. Cons:- Choices for users will be restricted. Clusters will not be dynamic. If a new event occurs, the predefined tags will miss it. Take the message, delete the stopwords [ predefined in a dictionary ] and apply some clustering algorithm to make a cluster and depending on its popularity, display the cluster. The cluster will be maintained according to its sustained popularity. New messages will be skimmed and assigned to corresponding clusters. Pros:- Dynamic clustering based on the popularity of the event/accident. Cons:- Increased complexity. More server resources required. I would like to know whether there are any other approaches to this problem. Or are there any ways of improving the above mentioned methods? Also suggest some good clustering algorithms.I think "K-Nearest Clustering" algorithm is apt for this situation.

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