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• What should every developer know about databases?

  - by Aaronaught

  Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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• Sort on DataView does not work if DataTable has zero rows

  - by BigBlondeViking

  We have a WPF app that has a DataGrid insode a ListView. private DataTable table_; We do a bunch or dynamic column generation ( depending on the report we are showing ) We then do the a query and fill the DataTable row by row, this query may or may not have data.( not the problem, an empty grid is expected ) We set the ListView's ItemsSource to the DefaultView of the DataTable. lv.ItemsSource = table_.DefaultView; We then (looking at the user's pass usage of the app, set the sort on the column) Sort Method below: private void Sort(string sortBy, ListSortDirection direction) { var dataView = CollectionViewSource.GetDefaultView(lv.ItemsSource); dataView.SortDescriptions.Clear(); var sd = new SortDescription(sortBy, direction); dataView.SortDescriptions.Add(sd); dataView.Refresh(); } In the Zero DataTable rows scenario, the sort does not "hold"? and if we dynamically add rows they will not be in sorted order. If the DataTable has at-least 1 row when the sort is applied, and we dynamically add rows to the DataTable, the rows com in sorted correctly. I have built a standalone app that replicate this... It is an annoyance and I can add a check to see if the DataTable was empty, and re-sort... Anyone know whats going on here, and am I doing something wrong? FYI: What we based this off if comes from the MSDN as well: http://msdn.microsoft.com/en-us/library/ms745786.aspx

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• My Rails app is returning HTTP 500 for all its URLs, but nothing shows up in the log file. How can I

  - by mipadi

  I have a Rails app that is running on a production server with Apache and Phusion Passenger. The app works fine locally when using Mongrel, but whenever I try to load a URL on the production server, it returns HTTP 500. I know the server is working properly, because I can get the static elements of the application (e.g., JavaScript files, stylesheets, images) just fine. I've also checked the Passenger status and it is loading the app (it must be, since the app's 500 Internal Server Error page is returned, not just the default Apache one). Also, when I load the app via script/console production and do something like app.get("/"), 500 is also returned. The problem is that there is nothing in the log files to indicate the problem. production.log is empty. The Apache error logs show no problems with Apache, either. I'm stumped as to what's going on and I'm not sure how to diagnose the problem. I know I may have been a bit vague, but can anyone give a suggestion on what the problem may be? Or at least a way I can go about diagnosing it?

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• stdexcept On Android

  - by David R.

  I'm trying to compile SoundTouch on Android. I started with this configure line: ./configure CPPFLAGS="-I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/" LDFLAGS="-Wl,-rpath-link=/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/lib -L/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/lib -nostdlib -lc" --host=arm-eabi --enable-shared=yes CFLAGS="-nostdlib -O3 -mandroid" host_alias=arm-eabi --no-create --no-recursion Because the Android NDK targets ARM, I also had to change the Makefile to remove the -msse2 flags to progress. When I run 'make', I get: /bin/sh ../../libtool --tag=CXX --mode=compile arm-eabi-g++ -DHAVE_CONFIG_H -I. -I../../include -I../../include -I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/ -O3 -fcheck-new -I../../include -g -O2 -MT FIRFilter.lo -MD -MP -MF .deps/FIRFilter.Tpo -c -o FIRFilter.lo FIRFilter.cpp libtool: compile: arm-eabi-g++ -DHAVE_CONFIG_H -I. -I../../include -I../../include -I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/ -O3 -fcheck-new -I../../include -g -O2 -MT FIRFilter.lo -MD -MP -MF .deps/FIRFilter.Tpo -c FIRFilter.cpp -o FIRFilter.o FIRFilter.cpp:46:21: error: stdexcept: No such file or directory FIRFilter.cpp: In member function 'virtual void soundtouch::FIRFilter::setCoefficients(const soundtouch::SAMPLETYPE*, uint, uint)': FIRFilter.cpp:177: error: 'runtime_error' is not a member of 'std' FIRFilter.cpp: In static member function 'static void* soundtouch::FIRFilter::operator new(size_t)': FIRFilter.cpp:225: error: 'runtime_error' is not a member of 'std' make[2]: *** [FIRFilter.lo] Error 1 make[1]: *** [all-recursive] Error 1 make: *** [all-recursive] Error 1 This isn't very surprising, since the -nostdlib flag was required. Android seems to have neither stdexcept nor stdlib. How can I get past this block of compiling SoundTouch? At a guess, there may be some flag I don't know about that I should use. I could refactor the code not to use stdexcept. There may be a way to pull in the original stdexcept source and reference that. I might be able to link to a precompiled stdexcept library.

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• Import package problem in GWT

  - by Krt_Malta

  Hi! I'm developing an app using GWT Eclipse plug-in. (I'm also using GWT Designer but I don't think the problem is here). Previously when I wanted to communicate with a web service I created, I produced the "skeleton" classes from the WSDL url using Sun's wsimport tool. Then I would add the classes generated to a class folder in my Eclipse project. All worked well. However this doesn't seem to be working with GWT. I have these: VideoTutorialServiceService service = new VideoTutorialServiceService(); VideoTutorialService port = service.getVideoTutorialServicePort(); and I have VideoTutorialServiceService and VideoTutorialService underlined in red, the error saying videotutorialservice.VideoTutorialServiceService can not be found in source packages. Check the inheritance chain from your module; it may not be inheriting a required module or a module may not be adding its source path entries properly. .... I googled about it but I got confused. I'm a beginnier in GWT. How can I resolve this please? Thanks and regards, Krt_Malta

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• Updating extra attributes in a has_many, :through relationship using Rails

  - by Robbie

  I've managed to set up a many-to-many relationship between the following models Characters Skills PlayerSkills PlayerSkills, right now, has an attribute that Skills don't normally have: a level. The models look something like this (edited for conciseness): class PlayerSkill < ActiveRecord::Base belongs_to :character belongs_to :skill end class Skill < ActiveRecord::Base has_many :player_skills has_many :characters, :through => :player_skills attr_accessible :name, :description end class Character < ActiveRecord::Base belongs_to :user has_many :player_skills has_many :skills, :through => :player_skills end So nothing too fancy in the models... The controller is also very basic at this point... it's pretty much a stock update action. The form I'm looking to modify is characters#edit. Right now it renders a series of checkboxes which add/remove skills from the characters. This is great, but the whole point of using has_many :through was to track a "level" as well. Here is what I have so far: - form_for @character do |f| = f.error_messages %p = f.label :name %br = f.text_field :name %p = f.label :race %br = f.text_field :race %p = f.label :char_class %br = f.text_field :char_class %p - @skills.each do |skill| = check_box_tag "character[skill_ids][]", skill.id, @character.skills.include?(skill) =h skill.name %br %p = f.submit After it renders "skill.name", I need it to print a text_field that updates player_skill. The problem, of course, is that player_skill may or may not exist! (Depending on if the box was already ticked when you loaded the form!) From everything I've read, has_many :through is great because it allows you to treat the relationship itself as an entity... but I'm completely at a loss as to how to handle the entity in this form. As always, thanks in advance for any and all help you can give me!

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• What headaches should I expect from using Trac?

  - by Dolph Mathews

  No tool is perfect, and I'm about to start several long-term projects using Trac, and wanted a heads up of the kinds of problems I may or may not experience with it. In other words, Trac meets my needs in the short term, and I've already made the decision to use it, but I want to know what to expect down the road. I am not looking for: "Use product X instead of Trac because..." answers. "Trac is great because..." answers. A comparison to any other specific system. "Trac doesn't support Feature X" answers. I can read the feature list too, thank you very much. I am looking for: "Feature X does not behave as expected..." "Trac behaves oddly when..." "Trac doesn't fully support..." "Trac itself has a known bug that will likely never be fixed..." And especially "Trac can't handle..." etc So, what Trac-induced headaches do I have to look forward to? For future reference, this question was asked while Trac v0.11 was the latest stable release.

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• What framework would allow for the largest coverage of freelance developers in the media/digital mar

  - by optician

  This question is not about which is the best, it is about which makes the most business sense to use as a company's platform of choice for ongoing freelance development. I'm currently trying to decide what framework to move my company in regarding frameworks for web application work. Options are ASP.NET MVC Django CakePHP/Symfony etc.. Struts Pearl on Rails Please feel free to add more to the discussion. I currently work in ASP.NET MVC in my Spare time, and find it incredibly enjoyable to work with. It is my first experince with an MVC framework for the web, so I can't talk on the others. The reason for not pushing this at the company is that I feel that there are not many developers in the Media/Marketing world who would work with this, so it may be hard to extend the team, or at least cost more. I would like to move into learning and pushing Django, partly to learn python, partly to feel a bit cooler (all my geeky friends use Java/Python/c++). Microsoft is the dark side to most company's I work with (Marketing/Media focused). But again I'm worried about developers in this sector. PHP seems like the natural choice, but I'm scared by the sheer amount of possible frameworks, and also that the quality of developer may be lower. I know there are great php developers out there, but how many of them know multiple frameworks? Are they similar enough that anyone decent at php can pick them up? Just put struts in the list as an option, but personally I live with a Java developer, and considering my experience with c#, I'm just not that interested in learning Java (selfish personal geeky reasons) Final option was a joke http://www.bbc.co.uk/blogs/radiolabs/2007/11/perl_on_rails.shtml

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• TCP: Address already in use exception - possible causes for client port? NO PORT EXHAUSTION

  - by TomTom

  Hello, stupid problem. I get those from a client connecting to a server. Sadly, the setup is complicated making debugging complex - and we run out of options. The environment: *Client/Server system, both running on the same machine. The client is actually a service doing some database manipulation at specific times. * The cnonection comes from C# going through OleDb to an EasySoft JDBC driver to a custom written JDBC server that then hosts logic in C++. Yeah, compelx - but the third party supplier decided to expose the extension mechanisms for their server through a JDBC interface. Not a lot can be done here ;) The Symptom: At (ir)regular intervals we get a "Address already in use: connect" told from the JDBC driver. They seem to come from one particular service we run. Now, I did read all the stuff about port exhaustion. This is why we have a little tool running now that counts ports and their states every minute. Last time this happened, we had an astonishing 370 ports in use, with the count rising to about 900 AFTER the error. We aleady patched the registry (it is a windows machine) to allow more than the 5000 client ports standard, but even then, we are far far from that limit to start with. Which is why I am asking here. Ayneone an ide what ELSE could cause this? It is a Windows 2003 Server machine, 64 bit. The only other thing I can see that may cause it (but this functionality is supposedly disabled) is Symantec Endpoint Protection that is installed on the server - and being capable of actinc as a firewall, it could possibly intercept network traffic. I dont want to open a can of worms by pointing to Symantec prematurely (if pointing to Symantec can ever be seen as such). So, anyone an idea what else may be the cause? Thanks

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• iPhone OS: Strategies for high density image work

  - by Jasconius

  I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time. I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases. This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory. Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility. I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following: 1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM 2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain 3) Anything dealing with memory paging particularly as it pertains to images I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.

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• How to define index by several columns in hibernate entity?

  - by foobar

  Morning. I need to add indexing in hibernate entity. As I know it is possible to do using @Index annotation to specify index for separate column but I need an index for several fields of entity. I've googled and found jboss annotation @Table, that allows to do this (by specification). But (I don't know why) this functionality doesn't work. May be jboss version is lower than necessary, or maybe I don't understant how to use this annotation, but... complex index is not created. Why index may not be created? jboss version 4.2.3.GA Entity example: package somepackage; import org.hibernate.annotations.Index; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; @Entity @org.hibernate.annotations.Table(appliesTo = House.TABLE_NAME, indexes = { @Index(name = "IDX_XDN_DFN", columnNames = {House.XDN, House.DFN} ) } ) public class House { public final static String TABLE_NAME = "house"; public final static String XDN = "xdn"; public final static String DFN = "dfn"; @Id @GeneratedValue private long Id; @Column(name = XDN) private long xdn; @Column(name = DFN) private long dfn; @Column private String address; public long getId() { return Id; } public void setId(long id) { this.Id = id; } public long getXdn() { return xdn; } public void setXdn(long xdn) { this.xdn = xdn; } public long getDfn() { return dfn; } public void setDfn(long dfn) { this.dfn = dfn; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } } When jboss/hibernate tries to create table "house" it throws following exception: Reason: org.hibernate.AnnotationException: @org.hibernate.annotations.Table references an unknown table: house

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• What is default javac source mode (assert as identifier compilation)?

  - by waste

  According to Orcale's Java7 assert guide: source mode 1.3 (default) — the compiler accepts programs that use assert as an identifier, but issues warnings. In this mode, programs are not permitted to use the assert statement. source mode 1.4 — the compiler generates an error message if the program uses assert as an identifier. In this mode, programs are permitted to use the assert statement. I wrote such class: package mm; public class ClassTest { public static void main(String[] arg) { int assert = 1; System.out.println(assert); } } It should compile fine if Oracle's info right (1.3 is default source mode). But I got errors like this: $ javac -version javac 1.7.0_04 $ javac -d bin src/mm/* src\mm\ClassTest.java:5: error: as of release 1.4, 'assert' is a keyword, and may not be used as an identifier int assert = 1; ^ (use -source 1.3 or lower to use 'assert' as an identifier) src\mm\ClassTest.java:6: error: as of release 1.4, 'assert' is a keyword, and may not be used as an identifier System.out.println(assert); ^ (use -source 1.3 or lower to use 'assert' as an identifier) 2 errors I added manually -source 1.3 and it issued warnings but compiled fine. It seems that Oracle's information is wrong and 1.3 is not default source mode. Which one is it then?

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• Extracting email addresses in an html block in ruby/rails

  - by corroded

  I am creating a parser that wards off against spamming and harvesting of emails from a block of text that comes from tinyMCE (so it may or may not have html tags in it) I've tried regexes and so far this has been successful: /\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b/i problem is, i need to ignore all email addresses with mailto hrefs. for example: <a href="mailto:[email protected]">[email protected]</a> should only return the second email add. To get a background of what im doing, im reversing the email addresses in a block so the above example would look like this: <a href="mailto:[email protected]">moc.liam@tset</a> problem with my current regex is that it also replaces the one in href. Is there a way for me to do this with a single regex? Or do i have to check for one then the other? Is there a way for me to do this just by using gsub or do I have to use some nokogiri/hpricot magicks and whatnot to parse the mailtos? Thanks in advance! Here were my references btw: so.com/questions/504860/extract-email-addresses-from-a-block-of-text so.com/questions/1376149/regexp-for-extracting-a-mailto-address im also testing using this: http://rubular.com/ edit here's my current helper code: def email_obfuscator(text) text.gsub(/\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b/i) { |m| m = "<span class='anti-spam'>#{m.reverse}</span>" } end which results in this: <a target="_self" href="mailto:<span class='anti-spam'>moc.liamg@tset</span>"><span class="anti-spam">moc.liamg@tset</span></a>

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• Are there any prototype-based languages with a whole development cycle?

  - by Kaveh Shahbazian

  Are there any real-world prototype-based programming languages with a whole development cycle? "A whole development cycle" like Ruby and Python: web frameworks, scripting/interacting with the system, tools for debugging, profiling, etc. Thank you A brief note on PBPLs: (let's call these languages PBPL : prototype-based programming language) There are some PBPLs out there. Some are being widely used like JavaScript (which Node.js may bring it into the field - or may not!). One other language is ActionScript which is also a PBPL but tightly bound to Flash VM (is it correct to say so?). From less known ones I can speak of Lua which has a strong reputation in game development (mostly spread by WOW) but never took off as a full language. Lua has a table concept which can provide you some sort of prototype based programming facility. There is also JScript (Windows scripting tool) which is already pointless by the newcomer PowerShell (I have used JScript to manipulate IIS but I never understood what is JScript!). Others can be named like io (indeed very very neat, you will fall in love with it; absolutely impossible to use) and REBOL (What is this all about? A proprietary scripting tool? You must be kidding!) and newLISP (Which is actually a full language, but no one ever heard about it). For sure there are much more to list here but either I do not remember or I did not understood them as a real world thing, like Self).

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• Proving that the distance values extracted in Dijkstra's algorithm is non-decreasing?

  - by Gail

  I'm reviewing my old algorithms notes and have come across this proof. It was from an assignment I had and I got it correct, but I feel that the proof certainly lacks. The question is to prove that the distance values taken from the priority queue in Dijkstra's algorithm is a non-decreasing sequence. My proof goes as follows: Proof by contradiction. Fist, assume that we pull a vertex from Q with d-value 'i'. Next time, we pull a vertex with d-value 'j'. When we pulled i, we have finalised our d-value and computed the shortest-path from the start vertex, s, to i. Since we have positive edge weights, it is impossible for our d-values to shrink as we add vertices to our path. If after pulling i from Q, we pull j with a smaller d-value, we may not have a shortest path to i, since we may be able to reach i through j. However, we have already computed the shortest path to i. We did not check a possible path. We no longer have a guaranteed path. Contradiction.

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• php & mySQL: Storing doc, xls, zip, etc. with limited access and archiving

  - by Devner

  Hi all, In my application, I have a provision for users to upload files like doc, xls, zip, etc. I would like to know how to store these files on my website and have only restricted people access it. I may have a group of people and let only these group access those uploaded files. I know that some may try to just copy the link to the document or the file and pass it to another (non-permitted) user and they can download it. So how can I prevent it? How can I check if the request to download the file was made by a legitimate user who has access to the file? The usernames of the group members are stored in the database along with the document name and location in the database so they can access it. But how do I prevent non-permitted users from being able to access that confidential data in all ways? With the above in mind, how do I store these documents? Do I store the documents in a blob column in the Database or just just let user upload to a folder and merely store the path to the file in the database? The security of the documents is of utmost importance. So any procedure that could facilitate this feature would definitely help. I am not into Object Oriented programming so if you have a simpler code that you would like to share with me, I would greatly appreciate it. Also how do I archive documents that are old? Like say there are documents that are 1 year old and I want to conserve my website space by archiving them but still make them available to the user when they need it. How do I go about this? Thank you.

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• Problem with GWT behind a reverse proxy - either nginx or apache

  - by Don Branson

  I'm having this problem with GWT when it's behind a reverse proxy. The backend app is deployed within a context - let's call it /context. The GWT app works fine when I hit it directly: http://host:8080/context/ I can configure a reverse proxy in front it it. Here's my nginx example: upstream backend { server 127.0.0.1:8080; } ... location / { proxy_pass http://backend/context/; } But, when I run through the reverse proxy, GWT gets confused, saying: 2009-10-04 14:05:41.140:/:WARN: Login: ERROR: The serialization policy file '/C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.140:/:WARN: Login: WARNING: Failed to get the SerializationPolicy 'C7F5ECA5E3C10B453290DE47D3BE0F0E' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. 2009-10-04 14:05:41.292:/:WARN: StoryService: ERROR: The serialization policy file '/0445C2D48AEF2FB8CB70C4D4A7849D88.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.292:/:WARN: StoryService: WARNING: Failed to get the SerializationPolicy '0445C2D48AEF2FB8CB70C4D4A7849D88' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. In other words, GWT isn't getting the word that it needs to prepend /context/ hen look for C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc, but only when the request comes throught proxy. A workaround is to add the context to the url for the web site: location /context/ { proxy_pass http://backend/context/; } but that means the context is now part of the url that the user sees, and that's ugly. Anybody know how to make GWT happy in this case? Software versions: GWT - 1.7.0 (same problem with 1.7.1) Jetty - 6.1.21 (but the same problem existed under tomcat) nginx - 0.7.62 (same problem under apache 2.x) I've looked at the traffic between the proxy and the backend using DonsProxy, but there's nothing noteworthy there.

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• Converting non-delimited text into name/value pairs in Delphi

  - by robsoft

  I've got a text file that arrives at my application as many lines of the following form: <row amount="192.00" store="10" transaction_date="2009-10-22T12:08:49.640" comp_name="blah " comp_ref="C65551253E7A4589A54D7CCD468D8AFA" name="Accrington "/> and I'd like to turn this 'row' into a series of name/value pairs in a given TStringList (there could be dozens of these <row>s in the file, so eventually I will want to iterate through the file breaking each row into name/value pairs in turn). The problem I've got is that the data isn't obviously delimited (technically, I suppose it's space delimited). Now if it wasn't for the fact that some of the values contain leading or trailing spaces, I could probably make a few reasonable assumptions and code something to break a row up based on spaces. But as the values themselves may or may not contain spaces, I don't see an obvious way to do this. Delphi' TStringList.CommaText doesn't help, and I've tried playing around with Delimiter but I get caught-out by the spaces inside the values each time. Does anyone have a clever Delphi technique for turning the sample above into something resembling this? ; amount="192.00" store="10" transaction_date="2009-10-22T12:08:49.640" comp_name="blah " comp_ref="C65551253E7A4589A54D7CCD468D8AFA" name="Accrington " Unfortunately, as is usually the case with this kind of thing, I don't have any control over the format of the data to begin with - I can't go back and 'make' it comma delimited at source, for instance. Although I guess I could probably write some code to turn it into comma delimited - would rather find a nice way to work with what I have though. This would be in Delphi 2007, if it makes any difference.

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• "Work stealing" vs. "Work shrugging"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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• ClassCastException When Calling an EJB Remotely that Exists on Same Server

  - by aaronvargas

  I have 2 ejbs. Ejb-A that calls Ejb-B. They are not in the same Ear. For portability Ejb-B may or may not exist on the same server. (There is an external property file that has the provider URLs of Ejb-B. I have no control over this.) Example Code: in Ejb-A EjbBDelegate delegateB = EjbBDelegateHelper.getRemoteDelegate(); // lookup from list of URLs from props... BookOfMagic bom = delegateB.getSomethingInteresting(); Use Cases/Outcomes: When Ejb-B DOES NOT EXIST on the same server as Ejb-A, everything works correctly. (it round-robbins through the URLs) When Ejb-B DOES EXIST on the same server, and Ejb-A happens to call Ejb-B on the same server, everything works correctly. When Ejb-B DOES EXIST on the same server, and Ejb-A calls Ejb-B on a different server, I get: javax.ejb.EJBException: nested exception is: java.lang.ClassCastException: $Proxy126 java.lang.ClassCastException: $Proxy126 I'm using Weblogic 10.0, Java 5, EJB3 Basically, if Ejb-B Exists on the server, it must be called ONLY on that server. Which leads me to believe that the class is getting loaded by a local classloader (on deployment?), then when called remotely, a different classloader is loading it. (causing the Exception) But it should work, as it should be Serialized into the destination classloader... What am I doing wrong?? Also, when reproducing this locally, Ejb-A would favor the Ejb-B on the same server, so it was difficult to reproduce. But this wasn't the case on other machines. NOTE: This all worked correctly for EJB2

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• Can't start the portable version of NetBeans 6.9.1 IDE

  - by Coder

  I downloaded the portable version of netbeans netbeans-6.9.1-201007282301-ml.zip from the netbeans site and changed the config file in etc/netbeans.conf as indicated on the netbeans site. The file contents are below. # ${HOME} will be replaced by JVM user.home system property #netbeans_default_userdir="${HOME}/.netbeans/6.9" netbeans_default_userdir=".netbeans/6.9" # Options used by NetBeans launcher by default, can be overridden by explicit # command line switches: netbeans_default_options="-J-client -J-Xss2m -J-Xms32m -J-XX:PermSize=32m -J-XX:MaxPermSize=200m -J-Dapple.laf.useScreenMenuBar=true -J-Dapple.awt.graphics.UseQuartz=true -J-Dsun.java2d.noddraw=true" # Note that a default -Xmx is selected for you automatically. # You can find this value in var/log/messages.log file in your userdir. # The automatically selected value can be overridden by specifying -J-Xmx here # or on the command line. # If you specify the heap size (-Xmx) explicitely, you may also want to enable # Concurrent Mark & Sweep garbage collector. In such case add the following # options to the netbeans_default_options: # -J-XX:+UseConcMarkSweepGC -J-XX:+CMSClassUnloadingEnabled -J-XX:+CMSPermGenSweepingEnabled # (see http://wiki.netbeans.org/wiki/view/FaqGCPauses) # Default location of JDK, can be overridden by using --jdkhome <dir>: #netbeans_jdkhome="/path/to/jdk" netbeans_jdkhome="C:\Program Files\Java\jdk1.6.0_24\" # Additional module clusters, using ${path.separator} (';' on Windows or ':' on Unix): #netbeans_extraclusters="/absolute/path/to/cluster1:/absolute/path/to/cluster2" # If you have some problems with detect of proxy settings, you may want to enable # detect the proxy settings provided by JDK5 or higher. # In such case add -J-Djava.net.useSystemProxies=true to the netbeans_default_options. But it refuses to start when i try to run it. If i change the JDK path to something incorrect it complains that it can't find the jdk so i think the jdk path is correct. It also creates a .netbeans directory when i try to start it. I don't see any errors and it just doesn't do anything else observable. Does anybody know how to set up this version of netbeans? Thanks.

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• Can I use a property placeholder with Spring EL?

  - by David Easley

  Before upgrading to Spring 3 I had this in my applicationContext.xml file: <bean class="com.northgateis.pole.ws.PolePayloadValidatingInterceptor"> <property name="validateRequest" value="${validateRequest}" /> <property name="validateResponse" value="${validateResponse}" /> </bean> where ${validateRequest) and ${validateRequest) refer to properties that may or may not be defined in my properties file. In Spring 2, if these proeprties were not present in the properties file the setters on the bean were not called and so the defaults hard-coded in PolePayloadValidatingInterceptor were used. After upgrading to Spring 3, it seems the behaviour is different: If the properties are not present in the properties file I get the following exception: SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'annotationMapping' defined in class path resource [com/northgateis/pole/ws/applicationContext-ws.xml]: Could not resolve placeholder 'validateRequest' at org.springframework.beans.factory.config.PropertyPlaceholderConfigurer.processProperties(PropertyPlaceholderConfigurer.java:272) at org.springframework.beans.factory.config.PropertyResourceConfigurer.postProcessBeanFactory(PropertyResourceConfigurer.java:75) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:640) at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:615) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:405) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:272) I tried dabbling with Spring EL but the following doesn't seem to work: <bean class="com.northgateis.pole.ws.PolePayloadValidatingInterceptor"> <property name="validateRequest" value="${validateRequest?:true}" /> <property name="validateResponse" value="${validateResponse?:false}" /> </bean> The value after the Elvis operator is always used, even when the properties are defined in the proeprties file. Interesting that the syntax is accepted. Any suggestions?

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• Dynamically bind argument and default value to existing function in Javascript

  - by Scott

  Let's suppose you have some function someFunc() already defined in javascript, that may or may not have its own argument set defined. Is it possible to write another function to add a required argument and set that argument to a default for someFunc()? Something like: var someFunc = function(arg1, arg2 ...){ Do stuff...} var addRequired = function(argName, argValue, fn) { Add the required default arg to a function... } addRequired("x", 20, someFunc); Now someFunc would be defined roughly like so: someFunc = function(x, arg1, arg2...) { x = 20; Do stuff... } What I am really seeking is to not only bind a this value to a function (which I already know how to achieve), but also bind another object reference to that same function (the function not being known ahead of time, as a user will define it, but then the user's code has access to this second object reference for use in their own function). So in my simple example above, the "20" value will actually be an object reference. Thanks for any help you can offer.

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• TFS Solution build cascading to several other builds even when common components were not modified

  - by Bob Palmer

  Hey all, here is the issue I am currently trying to work through. We are using Team Foundation Server 2008, and utilizing the automated build support out of the box. We have one very large project that encompasses a number of interrelated components and web sites, each of which is set up as a Visual Studio solution file. Many of these solutions are highly interrelated since they may contain applications, or contain common libraries or shared components. We have roughly 20 or so applications, three large web sites, and about 20 components. Each solution may include projects from other solutions. For example, a solution for a console app would also include the project files for all of the components it utilizes, since we need to ensure that when someone changes a component and rebuilds it, it is reflected in all of the projects that consume that component, and we can make sure nothing was broken. We have build projects for each solution, whether that's an application, component, or web site. For this example, we will call them solutions 01, 02, and 03. These reference multiple projects (both their own core project and test projects, plus the projects relating to various components). Solution 01 has projects A, B, and C. Solution 02 has projects C, D, and E. Solution 03 has projects E, F, and G. Now, for the problem. If I modify project A, the system will end up rebuilding all three solutions. Worse, all thirty solutions reference common projects used for data access (let's call it project H). Because they all share one project in common, if I modify any solution in my stack, even if it does not touch project H, I still end up kicking off every single build script. Any thoughts on how to address this? Ideally I would only want to kick off builds where their constituant projects were directly modified - i.e in the example below, if I modified project C, I would only rebuild solutions 01 and 02. Thanks!

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• Need some ignition for learning Embedded Systems

  - by Rahul

  I'm very much interested in building applications for Embedded Devices. I'm in my 3rd year Electrical Engineering and I'm passionate about coding, algorithms, Linux OS, etc. And also by Googling I found out that Linux OS is one of the best OSes for Embedded devices(may be/may not be). I want to work for companies which work on mobile applications. I'm a newbie/naive to this domain & my skills include C/C++ & MySQL. I need help to get started in the domain of Embedded Systems; like how/where to start off, Hardware prerequisites, necessary programming skills, also what kind of Embedded Applications etc. I've heard of ARM, firmware, PIC Micorcontrollers; but I don't know anything & just need proper introduction about them. Thanx. P.S: I'm currently reading Bjarne Struotsup's lecture in C++ at Texas A&M University, and one chapter in it describes about Embedded Systems Programming.

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