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• Java jasper report NullPointerException

  - by William Welch

  I am new to Java and I am running into this issue that I can't figure out. I inherited this project and I have the following code in one of my scriptlets: DefaultLogger.logMessage("DEBUG path: "+ reportFile.getPath()); DefaultLogger.logMessage("DEBUG parameters: "+ parameters); DefaultLogger.logMessage("DEBUG jr: "+ jr); bytes = JasperRunManager.runReportToPdf(reportFile.getPath(), parameters, jr); And I am getting the following results (the fourth line there is line 287 in FootwearReportsServlet.doGet): DEBUG path: C:\Development\JavaWorkspaces\Workspace1\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\RSLDevelopmentStandard\reports\templates\footwear\RslFootwearReport.jasper DEBUG parameters: {class_list_subreport=net.sf.jasperreports.engine.JasperReport@b07af1, signature_path=images/logo_reports.jpg, submission_id=20070213154168780, test_results_subreport=net.sf.jasperreports.engine.JasperReport@5795ce, logo_path=images/logos_3.gif, report_connection_secondary=com.mysql.jdbc.JDBC4Connection@2c39d2, testing_packages_subreport=net.sf.jasperreports.engine.JasperReport@1883d5f, signature_path2=images/logo_reports.jpg, tpid_subreport=net.sf.jasperreports.engine.JasperReport@17531fd, first_page_subreport=net.sf.jasperreports.engine.JasperReport@12504e0} DEBUG jr: net.sf.jasperreports.engine.data.JRMapCollectionDataSource@1630eb6 Apr 29, 2010 4:15:13 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet FootwearReportsServlet threw exception java.lang.NullPointerException at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:89) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:601) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:517) at net.sf.jasperreports.engine.JasperRunManager.runReportToPdf(JasperRunManager.java:385) at com.rsl.reports.FootwearReportsServlet.doGet(FootwearReportsServlet.java:287) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Unknown Source) What I can't figure out is where the null reference is. From the debug lines I can see that each parameter has a value. Could it be referring to a bad path to one of the images? Any ideas? For some reason my server won't start in debug mode in Eclipse so I am having trouble figuring this out.

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• Java web start - Unable to load resource

  - by CD

  Hi all, I've got a jar that loads great with java web starter when I browse through the IP address of the server. Once I try the server name instead I get the following exception: com.sun.deploy.net.FailedDownloadException: Unable to load resource: at com.sun.deploy.net.DownloadEngine.actionDownload(Unknown Source) at com.sun.deploy.net.DownloadEngine.getCacheEntry(Unknown Source) at com.sun.deploy.net.DownloadEngine.getCacheEntry(Unknown Source) at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(Unknown Source) at com.sun.deploy.net.DownloadEngine.getResourceCacheEntry(Unknown Source) at com.sun.deploy.net.DownloadEngine.getResource(Unknown Source) at com.sun.javaws.LaunchDownload$DownloadTask.call(Unknown Source) at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Any idea what should I look for?

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• GWT dev mode throws ArrayIndexOutOfBoundsException when compile GinjectorImpl.java

  - by Jiang Zhu

  I'm getting following exception when open my GWT app in development mode. the exact same code can compile successfully using mvn gwt:compile Caused by: java.lang.ArrayIndexOutOfBoundsException: 3667 at com.google.gwt.dev.asm.ClassReader.readClass(ClassReader.java:1976) at com.google.gwt.dev.asm.ClassReader.accept(ClassReader.java:464) at com.google.gwt.dev.asm.ClassReader.accept(ClassReader.java:420) at com.google.gwt.dev.shell.rewrite.HasAnnotation.hasAnnotation(HasAnnotation.java:45) at com.google.gwt.dev.shell.CompilingClassLoader.findClass(CompilingClassLoader.java:1100) at com.google.gwt.dev.shell.CompilingClassLoader.loadClass(CompilingClassLoader.java:1203) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:247) at com.google.gwt.dev.shell.ModuleSpace.loadClassFromSourceName(ModuleSpace.java:665) at com.google.gwt.dev.shell.ModuleSpace.rebindAndCreate(ModuleSpace.java:468) at com.google.gwt.dev.shell.GWTBridgeImpl.create(GWTBridgeImpl.java:49) at com.google.gwt.core.shared.GWT.create(GWT.java:57) at com.google.gwt.core.client.GWT.create(GWT.java:85) at ... I overdid ModuleSpace.java and printed out the class name at line 665 before Class.forName() which points out it is trying to load the generated GinjectorImpl.java I found out my generated GinjectorImpl.java is about 9MB and with 100K+ lines of code. When I randomly remove some modules from my GWT app it works again, so I'm guessing it is too large for ASM to compile. Any suggestions? Thanks Environment: GWT 2.5.0, GIN 1.5.0, gwt-maven-plugin 2.5.0, Java 6 SE

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• Null Pointer Exception while using Java Compiler API

  - by java_geek

  MyClass.java: package test; public class MyClass { public void myMethod(){ System.out.println("My Method Called"); } } Listing for SimpleCompileTest.java that compiles the MyClass.java file. SimpleCompileTest.java: package test; import javax.tools.*; public class SimpleCompileTest { public static void main(String[] args) { String fileToCompile = "test" + java.io.File.separator +"MyClass.java"; JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); int compilationResult = compiler.run(null, null, null, fileToCompile); if(compilationResult == 0){ System.out.println("Compilation is successful"); }else{ System.out.println("Compilation Failed"); } } } I am executing the SimpleCompileTest class and getting a NullPointerException. The ToolProvider.getSystemJavaCompiler() is returning null. Can someone tell me what is wrong with the code

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• When can we expect Core JEE Patterns from SUN/Oracle like we already have for J2EE?

  - by Digambar Daund

  Just like we have www.corej2eepatterns.com for J2EE, when can we expect any resource(book) on patterns for JEE5/6?

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• Problem changing Java version using alternatives

  - by Brian Lewis

  I'm not quite sure how I got into this mess, but for some reason I'm not able to change the current version of Java using alternatives. I can run alternatives --config java and type my selection but when I echo the version number for either java or javac, it spits back out 1.5 every time (despite alternatives showing the current version is 1.6). The server I'm working with is running RHEL5, by the way. I have verified that the paths used in alternatives are pointing to the correct directories. Here's some output from my session: [brilewis@myserver]$ sudo /usr/sbin/update-alternatives --config java There are 3 programs which provide 'java'. Selection Command ** 1 /usr/lib/jvm/jre-1.4.2-gcj/bin/java + 2 /usr/java/jdk1.5.0_10/bin/java 3 /usr/java/jdk1.6.0_16/bin/java Enter to keep the current selection[+], or type selection number: 3 [brilewis@myserver]$ java -version java version "1.5.0_10" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_10-b03) Java HotSpot(TM) Server VM (build 1.5.0_10-b03, mixed mode) [brilewis@myserver]$ sudo /usr/sbin/update-alternatives --config java There are 3 programs which provide 'java'. Selection Command ** 1 /usr/lib/jvm/jre-1.4.2-gcj/bin/java 2 /usr/java/jdk1.5.0_10/bin/java + 3 /usr/java/jdk1.6.0_16/bin/java Enter to keep the current selection[+], or type selection number:

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• Java compilers or JVM languages that support goto?

  - by unknown

  Is there a java compiler flag that allows me to use goto as a valid construct? If not, are there any third-party java compilers that supports goto? If not, are there any other languages that support goto while at the same time can easily call methods written in Java? The reason is I'm making a language that is implemented in Java. Gotos are an important part of my language; I want to be able to compile it to native or JVM bytecode, although it has to be able to easily use Java libraries (ie. C supports goto, but to use it I'd have to rewrite the libraries in C). I want to generate C or Java, etc source files, and not bytecode or machine code. I'm using a third-party compiler to do that.

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• java , eclipse jar problem

  - by Raxvan

  Hello , i'm kind of new to java. I use eclipse and i imported some jar files with some classes by going to properties - Add External Jars; The problem is that when i try to use a class from the jar i get the following exception: Exception in thread "main" java.lang.NoClassDefFoundError: nextapp/echo2/app/event/ActionListener at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.access$000(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at Program.main(Program.java:12) Caused by: java.lang.ClassNotFoundException: nextapp.echo2.app.event.ActionListener at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) ... 13 more The class is supposed to create a window, i guess that the jar has to import somehow other stuff or something like that, How can i fix this? PS. Sorry for the bad code , i don't know tags here. thansk, Raxvan

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• Eclipse Execute from Home - Eclipse.org Version

  - by sayth

  Due to a lot of minor errors with the eclipse from the repository( cannot install mylyn or pydev due to unmet dependencies) I manually downloaded from eclipse.org. I have not had this problem before but when I go to ~/eclipse (where I extracted the zip) and try to run eclipse it will not run. From the command line I just get eclipse not installed use sudo apt-get to install it. I know I have java installed. sayth@sayth-TravelMate-5740G:~$ java -version java version "1.6.0_23" OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre10-0ubuntu5) OpenJDK Server VM (build 20.0-b11, mixed mode) how can I get eclipse to load normally? Edit I removed the openjdk and installed oracle java to /usr/java I then create a symbolic link sayth@sayth-TravelMate-5740G:~/eclipse$ sudo ln -s /usr/java ~/eclipse/jre However still the error. sayth@sayth-TravelMate-5740G:~/eclipse$ java eclipse.jar Exception in thread "main" java.lang.NoClassDefFoundError: eclipse/jar Caused by: java.lang.ClassNotFoundException: eclipse.jar at java.net.URLClassLoader$1.run(URLClassLoader.java:217) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:321) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294) at java.lang.ClassLoader.loadClass(ClassLoader.java:266) Could not find the main class: eclipse.jar. Program will exit.

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• Distinguishing repetitive code with the same implementation

  - by KyelJmD

  Given this sample code import java.util.ArrayList; import blackjack.model.items.Card; public class BlackJackPlayer extends Player { private double bet; private Hand hand01 = new Hand(); private Hand hand02 = new Hand(); public void addCardToHand01(Card c) { hand01.addCard(c); } public void addCardToHand02(Card c) { hand02.addCard(c); } public void bustHand01() { hand01.setBust(true); } public void bustHand02() { hand02.setBust(true); } public void standHand01() { hand01.setStand(true); } public void standHand02() { hand02.setStand(true); } public boolean isHand01Bust() { return hand01.isBust(); } public boolean isHand02Bust() { return hand02.isBust(); } public boolean isHand01Standing() { return hand01.isStanding(); } public boolean isHand02Standing() { return hand02.isStanding(); } public int getHand01Score(){ return hand01.getCardScore(); } public int getHand02Score(){ return hand02.getCardScore(); } } Is this considered as a repetitive code? providing that each method is operating a seperate field but doing the same implementation ? Note that hand01 and hand02 should be distinct. if this is considered as repetitive code, how would I address this? providing that each hand is a seperate entity

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• who are software design engineers?

  - by Sepala

  My question is, who are software design engineers? And, what is the meaning of the following statement (from a software design engineer job ad)? "Application domain knowledge is essential and....." What is application domain? SDLC? My hope is to become a software engineer one day (OK, to be honest, more than that. I need to be a legend), that who do programming (They say this job has no programming). I am following final year of my Bsc(Hons) in computing and I have completed a foreign diploma, majoring software engineering - Java technologies. Will this job experience help me out to get a job in my desired position, which is mentioned above, after the degree? Wikipedia and google never gave a clear straight forward answer!! Please help!

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• Java crashes on lubuntu but not Ubuntu

  - by Echogene

  I have lubuntu and Ubuntu partitions on my drive. I've been having an interesting time with the new lubuntu partition. I've encountered strange things with the game Minecraft, Java and graphics drivers on the lubuntu partition. Firstly, I'll say that Minecraft runs fine at about 60fps on the Ubuntu partition with the latest drivers. (This is lower than it should be as it's a pretty decent graphics card [Radeon HD 5700].) When I first started lubuntu, I tried to see if I could get Minecraft running on Java. Java crashed when loading the main game graphics on both Sun and OpenJDK without proprietary drivers. Java also crashed on both Javas with proprietary drivers after the necessary restart. However, after disabling (with 'remove' button) the proprietary drivers with jockey-gtk in the session after the restart to install the drivers, Minecraft ran very well at ~120fps. This didn't continue after another restart, when it ran at 9fps. After failing thereafter on lubuntu to get it working at 15fps, I tried reinstalling lubuntu and installed the exact same driver (the latest one, not the one appearing on jockey) and Java versions as on Ubuntu. That is, now Ubuntu and lubuntu have the same graphics driver and Java version. Minecraft still crashes in the same way on lubuntu but works fine on Ubuntu. I would appreciate any explanation for any of these events. What differences between lubuntu and Ubuntu could cause this? Edit: After installing the 32bit driver version on lubuntu (seeing as lubuntu is 32bit), I have Java "working" for Minecraft. However, it is at <15fps again and it can't log in to servers as it takes too long.

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• Code Structure / Level Design: Plants vs Zombies game level dissection

  - by lalan

  Hi Friends, I am interested in learning the class structure of Plants vs Zombies, particularly level design; for those who haven't played it - this video contains nice play-through: http://www.youtube.com/watch?v=89DfdOIJ4xw. How would I go ahead and design the code, mostly structure & classes, which allows for maximum flexibility & clean development? I am familiar with data driven design concepts, and would use events to handle most of dynamic behavior. Dissection at macro level: (Once every Level) Load tilemap, props, etc -- basically build the map (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) Show Enemies you'll face during present level (Once every Level) Unit Selection Window/Panel - selection of defensive plants (Once every Level) Camera Movement - might consider it as short cut-scene (Once every Level) HUD Creation - based on unit selection (Level Loop) Enemy creation - based on types of zombies allowed (Level Loop) Sun/Resource generation (Level Loop) Show messages like 'huge wave of zombies coming', 'final wave' (Level Loop) Other unique events - Spawn gifts, money, tombstones, etc (Once every Level) Unlock new plant Potential game scripts: a) Level definitions: Level_1_1.xml, Level_1_2.xml, etc. Level_1_1.xml :: Sample script <map> <tilemap>tilemapFrontLawn</tilemap> <SpawnPoints> tiles where particular type of zombies (land vs water) may spawn</spawnPoints> <props> position, entity array -- lawnmower, </props> </map> <zombies> <... list of zombies who gonna attack by ids...> </zombies> <plants> <... list by plants which are available for defense by ids...> </plants> <progression> <ZombieWave name='first wave' spawnScript='zombieLightWave.lua' unlock='null'> <startMessages time=1.5>Ready</startMessages> <endMessages time=1.5>Huge wave of zombies incoming</endMessages> </ZombieWave> </progression> b) Entities definitions: .xmls containing zombies, plants, sun, lawnmower, coins, etc description. Potential classes: //LevelManager - Based on the level under play, it will load level script. Few of the // functions it may have: class LevelManager { public: bool load(string levelFileName); bool enter(); bool update(float deltatime); bool exit(); private: LevelData* mLevelData; } // LevelData - Contains the details of level loaded by LevelManager. class LevelData { private: string file; // array of camera,dialog,attackwaves, etc in active level LevelCutSceneCamera** mArrayCutSceneCamera; LevelCutSceneDialog** mArrayCutSceneDialog; LevelAttackWave** mArrayAttackWave; .... // which camera,dialog,attackwave is active in level uint mCursorCutSceneCamera; uint mCursorCutSceneDialog; uint mCursorAttackWave; public: // based on cursor, get the next camera,dialog,attackwave,etc in active level // return false/true based on failure/success bool nextCutSceneCamera(LevelCutSceneCamera**); bool nextCutSceneDialog(LevelCutSceneDialog**); } // LevelUnderPlay- LevelManager class LevelUnderPlay { private: LevelCutSceneCamera* mCutSceneCamera; LevelCutSceneDialog* mCutSceneDialog; LevelAttackWave* mAttackWave; Entities** mSelectedPlants; Entities** mAllowedZombies; bool isCutSceneCameraActive; public: bool enter(); bool update(float deltatime); bool exit(); } I am totally confused.. :( Does it make sense of using class composition (have flat class hierarchy) for managing levels. Is it a good idea to just add/remove/update sprites (or any drawable stuff) to current scene from LevelManager or LevelUnderPlay? If I want to make non-linear level design, how should I go ahead? Perhaps I would need a LevelProgression class, which would decide what to do based on decision tree. Any suggestions would be appreciated very much. Thank for your time, lalan

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• Relationship between TDD and Software Architecture/Design

  - by Christopher Francisco

  I'm new to TDD and have been reading the theory since applying it is more complicated than it sounds when you're learning by yourself. As far as I know, the objective is to write test cases for each requirement and run the test so it fails (to prevent a false positive). Afterward, you should write the minimum amount of code that can pass the test and move to the next one. That being said, is it true that you get a fast development, but what about the code itself? this theory makes me think you are not considering things like abstraction, delegation of responsibilities, design patterns, architecture and others since you're just writing "the minimum amount of code that can pass the test". I know I'm probably wrong because if this were true, we'd have a lot of crappy developers with poor software architecture and documentation so I'm asking for a guide here, what's the relationship between TDD and Software Architecture/Design?

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• Adventures in Windows 8: Understanding and debugging design time data in Expression Blend

  - by Laurent Bugnion

  One of my favorite features in Expression Blend is the ability to attach a Visual Studio debugger to Blend. First let’s start by answering the question: why exactly do you want to do that? Note: If you are familiar with the creation and usage of design time data, feel free to scroll down to the paragraph titled “When design time data fails”. Creating design time data for your app When a designer works on an app, he needs to see something to design. For “static” UI such as buttons, backgrounds, etc, the user interface elements are going to show up in Blend just fine. If however the data is fetched dynamically from a service (web, database, etc) or created dynamically, most probably Blend is going to show just an empty element. The classical way to design at that stage is to run the application, navigate to the screen that is under construction (which can involve delays, need to log in, etc…), to measure what is on the screen (colors, margins, width and height, etc) using various tools, going back to Blend, editing the properties of the elements, running again, etc. Obviously this is not ideal. The solution is to create design time data. For more information about the creation of design time data by mocking services, you can refer to two talks of mine “Deep dive MVVM” and “MVVM Applied From Silverlight to Windows Phone to Windows 8”. The source code for these talks is here and here. Design time data in MVVM Light One of the main reasons why I developed MVVM Light is to facilitate the creation of design time data. To illustrate this, let’s create a new MVVM Light application in Visual Studio. Install MVVM Light from here: http://mvvmlight.codeplex.com (use the MSI in the Download section). After installing, make sure to read the Readme that opens up in your favorite browser, you will need one more step to install the Project Templates. Start Visual Studio 2012. Create a new MvvmLight (Win8) app. Run the application. You will see a string showing “Welcome to MVVM Light”. In the Solution explorer, right click on MainPage.xaml and select Open in Blend. Now you should see “Welcome to MVVM Light [Design]” What happens here is that Expression Blend runs different code at design time than the application runs at runtime. To do this, we use design-time detection (as explained in a previous article) and use that information to initialize a different data service at design time. To understand this better, open the ViewModelLocator.cs file in the ViewModel folder and see how the DesignDataService is used at design time, while the DataService is used at runtime. In a real-life applicationm, DataService would be used to connect to a web service, for instance. When design time data fails Sometimes however, the creation of design time data fails. It can be very difficult to understand exactly what is happening. Expression Blend is not giving a lot of information about what happened. Thankfully, we can use a trick: Attaching a debugger to Expression Blend and debug the design time code. In WPF and Silverlight (including Windows Phone 7), you could simply attach the debugger to Blend.exe (using the “Managed (v4.5, v4.0) code” option even for Silverlight!!) In Windows 8 however, things are just a bit different. This is because the designer that renders the actual representation of the Windows 8 app runs in its own process. Let’s illustrate that: Open the file DesignDataService in the Design folder. Modify the GetData method to look like this: public void GetData(Action<DataItem, Exception> callback) { throw new Exception(); // Use this to create design time data var item = new DataItem("Welcome to MVVM Light [design]"); callback(item, null); } Go to Blend and build the application. The build succeeds, but now the page is empty. The creation of the design time data failed, but we don’t get a warning message. We need to investigate what’s wrong. Close MainPage.xaml Go to Visual Studio and select the menu Debug, Attach to Process. Update: Make sure that you select “Managed (v4.5, v4.0) code” in the “Attach to” field. Find the process named XDesProc.exe. You should have at least two, one for the Visual Studio 2012 designer surface, and one for Expression Blend. Unfortunately in this screen it is not obvious which is which. Let’s find out in the Task Manager. Press Ctrl-Alt-Del and select Task Manager Go to the Details tab and sort the processes by name. Find the one that says “Blend for Microsoft Visual Studio 2012 XAML UI Designer” and write down the process ID. Go back to the Attach to Process dialog in Visual Studio. sort the processes by ID and attach the debugger to the correct instance of XDesProc.exe. Open the MainViewModel (in the ViewModel folder) Place a breakpoint on the first line of the MainViewModel constructor. Go to Blend and open the MainPage.xaml again. At this point, the debugger breaks in Visual Studio and you can execute your code step by step. Simply step inside the dataservice call, and find the exception that you had placed there. Visual Studio gives you additional information which helps you to solve the issue. More info and Conclusion I want to thank the amazing people on the Expression Blend team for being very fast in guiding me in that matter and encouraging me to blog about it. More information about the XDesProc.exe process can be found here. I had to work on a Windows 8 app for a few days without design time data because of an Exception thrown somewhere in the code, and it was really painful. With the debugger, finding the issue was a simple matter of stepping into the code until it threw the exception.   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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• Design review for application facing memory issues

  - by Mr Moose

  I apologise in advance for the length of this post, but I want to paint an accurate picture of the problems my app is facing and then pose some questions below; I am trying to address some self inflicted design pain that is now leading to my application crashing due to out of memory errors. An abridged description of the problem domain is as follows; The application takes in a “dataset” that consists of numerous text files containing related data An individual text file within the dataset usually contains approx 20 “headers” that contain metadata about the data it contains. It also contains a large tab delimited section containing data that is related to data in one of the other text files contained within the dataset. The number of columns per file is very variable from 2 to 256+ columns. The original application was written to allow users to load a dataset, map certain columns of each of the files which basically indicating key information on the files to show how they are related as well as identify a few expected column names. Once this is done, a validation process takes place to enforce various rules and ensure that all the relationships between the files are valid. Once that is done, the data is imported into a SQL Server database. The database design is an EAV (Entity-Attribute-Value) model used to cater for the variable columns per file. I know EAV has its detractors, but in this case, I feel it was a reasonable choice given the disparate data and variable number of columns submitted in each dataset. The memory problem Given the fact the combined size of all text files was at most about 5 megs, and in an effort to reduce the database transaction time, it was decided to read ALL the data from files into memory and then perform the following; perform all the validation whilst the data was in memory relate it using an object model Start DB transaction and write the key columns row by row, noting the Id of the written row (all tables in the database utilise identity columns), then the Id of the newly written row is applied to all related data Once all related data had been updated with the key information to which it relates, these records are written using SqlBulkCopy. Due to our EAV model, we essentially have; x columns by y rows to write, where x can by 256+ and rows are often into the tens of thousands. Once all the data is written without error (can take several minutes for large datasets), Commit the transaction. The problem now comes from the fact we are now receiving individual files containing over 30 megs of data. In a dataset, we can receive any number of files. We’ve started seen datasets of around 100 megs coming in and I expect it is only going to get bigger from here on in. With files of this size, data can’t even be read into memory without the app falling over, let alone be validated and imported. I anticipate having to modify large chunks of the code to allow validation to occur by parsing files line by line and am not exactly decided on how to handle the import and transactions. Potential improvements I’ve wondered about using GUIDs to relate the data rather than relying on identity fields. This would allow data to be related prior to writing to the database. This would certainly increase the storage required though. Especially in an EAV design. Would you think this is a reasonable thing to try, or do I simply persist with identity fields (natural keys can’t be trusted to be unique across all submitters). Use of staging tables to get data into the database and only performing the transaction to copy data from staging area to actual destination tables. Questions For systems like this that import large quantities of data, how to you go about keeping transactions small. I’ve kept them as small as possible in the current design, but they are still active for several minutes and write hundreds of thousands of records in one transaction. Is there a better solution? The tab delimited data section is read into a DataTable to be viewed in a grid. I don’t need the full functionality of a DataTable, so I suspect it is overkill. Is there anyway to turn off various features of DataTables to make them more lightweight? Are there any other obvious things you would do in this situation to minimise the memory footprint of the application described above? Thanks for your kind attention.

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• C++ Library API Design

  - by johannes

  I'm looking for a good resource for learning about good API design for C++ libraries, looking at shared objects/dlls etc. There are many resources on writing nice APIs, nice classes, templates and so on at source level, but barely anything about putting things together in shared libs and executables. Books like Large-Scale C++ Software Design by John Lakos are interesting but massively outdated. What I'm looking for is advice i.e. on handling templates. With templates in my API I often end up with library code in my executable (or other library) so if I fix a bug in there I can't simply roll out the new library but have to recompile and redistribute all clients of that code. (and yes, I know some solutions like trying to instantiate at least the most common versions inside the library etc.) I'm also looking for other caveats and things to mind for keeping binary compatibility while working on C++ libraries. Is there a good website or book on such things?

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• Composite-like pattern and SRP violation

  - by jimmy_keen

  Recently I've noticed myself implementing pattern similar to the one described below. Starting with interface: public interface IUserProvider { User GetUser(UserData data); } GetUser method's pure job is to somehow return user (that would be an operation speaking in composite terms). There might be many implementations of IUserProvider, which all do the same thing - return user basing on input data. It doesn't really matter, as they are only leaves in composite terms and that's fairly simple. Now, my leaves are used by one own them all composite class, which at the moment follows this implementation: public interface IUserProviderComposite : IUserProvider { void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider); } public class UserProviderComposite : IUserProviderComposite { public User GetUser(SomeUserData data) ... public void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider) ... } Idea behind UserProviderComposite is simple. You register providers, and this class acts as a reusable entry-point. When calling GetUser, it will use whatever registered provider matches predicate for requested user data (if that helps, it stores key-value map of predicates and providers internally). Now, what confuses me is whether RegisterProvider method (brings to mind composite's add operation) should be a part of that class. It kind of expands its responsibilities from providing user to also managing providers collection. As far as my understanding goes, this violates Single Responsibility Principle... or am I wrong here? I thought about extracting register part into separate entity and inject it to the composite. As long as it looks decent on paper (in terms of SRP), it feels bit awkward because: I would be essentially injecting Dictionary (or other key-value map) ...or silly wrapper around it, doing nothing more than adding entires This won't be following composite anymore (as add won't be part of composite) What exactly is the presented pattern called? Composite felt natural to compare it with, but I realize it's not exactly the one however nothing else rings any bells. Which approach would you take - stick with SRP or stick with "composite"/pattern? Or is the design here flawed and given the problem this can be done in a better way?

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• How do you approach database design?

  - by bron

  I am primarily a web developer and I have a couple of personal projects which I want to kick off. One thing that is bugging me is database design. I have gone through in school db normalization and stuff like that but it has been a couple of years ago and I have never had experience with relational database design except for school. So how you do you approach database from a web app perspective? How do you begin and what do you look out for? What are flags for caution?

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• What is Java used for these days?

  - by Barry Brown

  Java is fifteen years old. It started life as an alternative to C++ with a comprehensive standard library. Riding on the coattails of the Internet boom, it was popular for writing web applets. Its supposed portability was touted as a way to write desktop apps that would run on any platform. Now it's 2010. Applets are long gone. Desktop apps are giving way to web and mobile apps. Scripting languages are very popular, as is Flash, especially among web-centric developers. People have been chanting "Java's death is near" for several years. Yet a quick job search shows that Java is still a desired skill among programmers. So what is Java used for these days? What kinds of apps are you writing in Java? This should give us an idea of the "state of Java" today. Has the Java tide shifted from Swing desktop apps to Android mobile apps? If you write programs in a JVM language (such as Scala or Groovy), mention it.

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• Minecraft in jdk 1.7.0_u2 x64

  - by Nela Drobná

  I have Ubuntu 11.10 64-bit and I installed JDK 1.7.0 update 2 x64 via webupd8 page. But currently I have problem with minecraft game. After downloading launcher from Minecraft.net and lauch the game by java -jar /home/zrebec/Downloads/minecraft.jar launcehr is launched normaly, after login the game download the updates but then I got just the black screen with this in terminal: Setting user: zrebec, -356009615199623309 Exception in thread "Minecraft main thread" java.lang.UnsatisfiedLinkError: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: wrong ELF class: ELFCLASS32 (Possible cause: architecture word width mismatch) at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1928) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1825) at java.lang.Runtime.load0(Runtime.java:792) at java.lang.System.load(System.java:1059) at org.lwjgl.Sys$1.run(Sys.java:69) at java.security.AccessController.doPrivileged(Native Method) at org.lwjgl.Sys.doLoadLibrary(Sys.java:65) at org.lwjgl.Sys.loadLibrary(Sys.java:81) at org.lwjgl.Sys.<clinit>(Sys.java:98) at org.lwjgl.opengl.Display.<clinit>(Display.java:132) at net.minecraft.client.Minecraft.a(SourceFile:180) at net.minecraft.client.Minecraft.run(SourceFile:648) at java.lang.Thread.run(Thread.java:722) Please anyone can help me with this? I think that problem will be in architecture becase: liblwjgl.so: /home/zrebec/.minecraft/bin/natives/liblwjgl.so: wrong ELF class: ELFCLASS32 (Possible cause: architecture word width mismatch) Any idea please? I know, maybe this one is off topic because maybe its not Ubuntu problem maybe but in 64-bit works all perfectly and I think that accepted answer can help to many users and can make better playing games under linux. Really. Thank you very much for any idea.

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• How to design software when using BDD?

  - by Léster

  I'm working on a project right now and it's my first project using BDD. Up till now, the user stories have proven themselves a very valuable weapon to understand requirements and to specify the solution in a comprehensive, easy to understand language. My question is this: now that my user stories are complete, how do I design my solution? I understand that I derive behavior tests from my user stories, and I have to do UI design, but am I supposed to use good ol' UML? I'm under the impression that when using user stories, UML is left out; is this correct? Léster

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• Best Java Book(s) for an Experienced Developer

  - by Steven Elliott Jr

  I have been a .NET developer now for about the past 5/6 years give or take. I have never done any professional Java development and the last time I really touched it was probably back in college. I have been toying with the Scala language a little bit but nothing serious. Recently, I've been offered an opportunity to do some pretty cool work, but using Java instead of .NET. I think I can get by alright with my current skill set, meaning I already know how to program well and am familiar with languages such as C# and C++, etc. So, the syntax and all that language stuff are really not a problem. What I need is a really good reference book and a book about how to think in Java. Each language/Framework/Stack tries to address things a certain way and I'm sure Java is no different. What are some great Java books that you simply can't live without? Are there any books that talk about the most important parts of Java that must be understood before all else? As a side note, I will be doing mostly Java web development. Not really 100% on what types of stuff they are using for persistence, framework, server, etc. Thanks again for the consideration.

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• Why isn't Java used for modern web application development?

  - by Cliff

  As a professional Java programmer, I've been trying to understand - why the hate toward Java for modern web applications? I've noticed a trend that out of modern day web startups, a relatively small percentage of them appears to be using Java (compared to Java's overall popularity). When I've asked a few about this, I've typically received a response like, "I hate Java with a passion." But no one really seems to be able to give a definitive answer. I've also heard this same web startup community refer negatively to Java developers - more or less implying that they are slow, not creative, old. As a result, I've spent time working to pick up Ruby/Rails, basically to find out what I'm missing. But I can't help thinking to myself, "I could do this much faster if I were using Java," primarily due to my relative experience levels. But also because I haven't seen anything critical "missing" from Java, preventing me from building the same application. Which brings me to my question(s): Why is Java not being used in modern web applications? Is it a weakness of the language? Is it an unfair stereotype of Java because it's been around so long (it's been unfairly associated with its older technologies, and doesn't receive recognition for its "modern" capabilities)? Is the negative stereotype of Java developers too strong? (Java is just no longer "cool") Are applications written in other languages really faster to build, easier to maintain, and do they perform better? Is Java only used by big companies who are too slow to adapt to a new language?

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• How to fill certain application design learning "gaps"?

  - by e4rthdog

  In life it doesnt matter if you do one thing for 15 years. You will end up waking one day and asking stuff that are equal to "how do i walk?" :) My specific question is that as a new entrant to C# and OOP i am stepping into many little "details" that need to be addressed. Written a lot of code in VB.NET / cobol / simple php e.t.c surely does not help much into the OOP world... So , even after reading entry level books for C# and watching some videos i recently found out about the "factory model design" for applications. I would appreciate if any of you guys recomment some reading on application design architecture for further reading...

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