Stamping the version number and the build time of an application in a properties file so that it could be displayed by an application at runtime seemed like it should be a pretty straightforward task, although it took a bit of time to find a solution that didn’t require the timestamp, version, or ant-run plugins. I started with a version.txt file at the default package level in src/main/resources of my project, which looks as follows. version=${pom.version} build.date=${timestamp} By default the Maven resources plug-in will not do text substitution (filtering), so it will need to be enabled within the section of the pom.xml file. src/main/resources true Maven does actually define a ${maven.build.timestamp} property which in theory could have been used in the version.txt file, rather than the ${timestamp} property, but unfortunately a bug within Maven prevents the ${maven.build.timestamp} property from getting passed to the resource filtering mechanism. (issue:http://jira.codehaus.org/browse/MRESOURCES-99). The workaround is to create another property within the pom.xml file and set that new property to the timestamp value, in this case, the property name is “timestamp”, which is used above in the version.txt file. The maven.build.timestamp.format is an optional property for (obviously) defining the timestamp format. ${maven.build.timestamp} yyyy-MM-dd HH:mm Now, when the build is executed we end up with the version number and build time of the application in the version.txt file. Easy! version=1.0.2-SNAPSHOT build.date=2012-03-16 15:42

i want to like javafx, really i do. the return of the applet reminds me of the 90s which is nice. i also like the idea of being able to drag an applet into windows, ubuntu , and mac to run it as a desktop application. it's a whole new take on their "write once, run anywhere" promise and breathing some life into a platform that needs it. java used to be so trendy and cool, it was the "ruby on rails of the 90s" now it's seemingly destined to be the "cobol of the 20s". if javafx lives up to its promise it could turn things around. well, i guess android is technically leading a java revival today unless oracle's lawsuit forces google to move to a different language. so far though i've been a little disappointed with javafx. it's like an el camino, a strange combination of awt and swing that doesn't quite feel natural. i'm going to keep trying it anyway and hope that one day it catches up to c# 1.0. look, i know this sounds terribly cynical so far but you have to believe me when i say i'm trying to like it. the reality is, even if javafx is a little clunky now it's still a considerable improvement over swing. over the next few months i'm going to upgrade all my ugly swing applications to javafx. the first one is something called debigulator . it's a batch archive program that i wrote for myself but has been downloaded more than i expected. it's also one of the ugliest programs ever created. just look at this monstrosity: besides being unattractive it also doesn't resize well. javafx addresses both of those so i'm porting it. the first thing to go is that awful file browser in the top left region, i'm embarrassed to look at it. i think i'll replace it with a simple treeview. to create a treeview we first have to create a treeitem subclass to store in the tree. the api documentation for the javafx treeitem class includes a partial implementation of a file browser. i looked at it but went a different direction because it recursively populates the entire tree up front and doesn't deal with things like folder & file icons. instead i wanted to dynamically populate a node when it's expanded. the treeitem also needs to store the path to the file represented by each item but only show the folder or file name. alright, let's get our treeitem implementation started. the constructor and class members look a little something like: public class filepathtreeitem extends treeitem{ public static image foldercollapseimage=new image(classloader.getsystemresourceasstream("com/huguesjohnson/javafxfilebrowsedemo/folder.png")); public static image folderexpandimage=new image(classloader.getsystemresourceasstream("com/huguesjohnson/javafxfilebrowsedemo/folder-open.png")); public static image fileimage=new image(classloader.getsystemresourceasstream("com/huguesjohnson/javafxfilebrowsedemo/text-x-generic.png")); //this stores the full path to the file or directory private string fullpath; public string getfullpath(){return(this.fullpath);} private boolean isdirectory; public boolean isdirectory(){return(this.isdirectory);} public filepathtreeitem(path file){ super(file.tostring()); this.fullpath=file.tostring(); next we want to set the icon, full path, and isdirectory members. this would be a good time to mention that all the icons in this demo come from the tango library . //test if this is a directory and set the icon if(files.isdirectory(file)){ this.isdirectory=true; this.setgraphic(new imageview(foldercollapseimage)); }else{ this.isdirectory=false; this.setgraphic(new imageview(fileimage)); //if you want different icons for different file types this is where you'd do it } //set the value if(!fullpath.endswith(file.separator)){ //set the value (which is what is displayed in the tree) string value=file.tostring(); int indexof=value.lastindexof(file.separator); if(indexof>0){ this.setvalue(value.substring(indexof+1)); }else{ this.setvalue(value); } } now let's add the event handler for the node expanded event. that check for source.isexpanded() sure seems unnecessary. man that was a fun piece of unexpected behavior to track down. this.addeventhandler(treeitem.branchexpandedevent(),new eventhandler(){ @override public void handle(event e){ filepathtreeitem source=(filepathtreeitem)e.getsource(); if(source.isdirectory()&&source.isexpanded()){ imageview iv=(imageview)source.getgraphic(); iv.setimage(folderexpandimage); } try{ if(source.getchildren().isempty()){ path path=paths.get(source.getfullpath()); basicfileattributes attribs=files.readattributes(path,basicfileattributes.class); if(attribs.isdirectory()){ directorystream dir=files.newdirectorystream(path); for(path file:dir){ filepathtreeitem treenode=new filepathtreeitem(file); source.getchildren().add(treenode); } } }else{ //if you want to implement rescanning a directory for changes this would be the place to do it } }catch(ioexception x){ x.printstacktrace(); } } }); we'll wrap up this treeitem implementation with an handler for the node collapsed event. again the source.isexpanded() check really shouldn't be needed but just go ahead and remove it to see the goofiness that follows. this.addeventhandler(treeitem.branchcollapsedevent(),new eventhandler(){ @override public void handle(event e){ filepathtreeitem source=(filepathtreeitem)e.getsource(); if(source.isdirectory()&&!source.isexpanded()){ imageview iv=(imageview)source.getgraphic(); iv.setimage(foldercollapseimage); } } }); now we can go to work on the main program. here's all the basic stuff. public class javafxfilebrowsedemoapp extends application{ private treeview treeview; public static void main(string[] args){ launch(args); } @override public void start(stage primarystage){ //create tree pane vbox treebox=new vbox(); treebox.setpadding(new insets(10,10,10,10)); treebox.setspacing(10); now it's time to start populating the tree. we'll use the computer name as the root node. although i might go back and hide the root node since it's kind of pointless for this application. it's really just showing off how to get the name from the inetaddress class which you either already knew or didn't care about. //setup the file browser root string hostname="computer"; try{hostname=inetaddress.getlocalhost().gethostname();}catch(unknownhostexception x){} treeitem rootnode=new treeitem<>(hostname,new imageview(new image(classloader.getsystemresourceasstream("com/huguesjohnson/javafxfilebrowsedemo/computer.png")))); one nifty addition to jdk7 is the ability to list all the drives on the system. that comes in handy for the next step where we need to add all the drives under the root node. iterable rootdirectories=filesystems.getdefault().getrootdirectories(); for(path name:rootdirectories){ filepathtreeitem treenode=new filepathtreeitem(name); rootnode.getchildren().add(treenode); } rootnode.setexpanded(true); all that's left is to add the treeview to the window and show it. //create the tree view treeview=new treeview<>(rootnode); //add everything to the tree pane treebox.getchildren().addall(new label("file browser"),treeview); vbox.setvgrow(treeview,priority.always); //setup and show the window primarystage.settitle("javafx file browse demo"); stackpane root=new stackpane(); root.getchildren().addall(treebox); primarystage.setscene(new scene(root,400,300)); primarystage.show(); here's what the final product looks like, much cleaner than the awful swing version and less than half the code:

Marker Interfaces in Java have special significance because of the fact that they have no methods declared in them which means that the classes implementing these interfaces don't have to override any of the methods. A few of the marker interfaces already exist in the JDK like Serializable and Cloneable. One can also create their own custom interfaces which doesn't have any method. The purpose of these interfaces is to force some kind of functionality in the classes by providing some functionality to a class if it implements the marker interface. A common question asked very frequently is about Runnable interface being marker or not. Runnable interface is not marker because Runnable interface has the public void run() method declared inside it. A very good example of marker interface is Serializable where the class implements can be used with ObjectOutputStream and ObjectInputStream classes. The Java language specification doesn't itself define the term marker interface and the term has been coined by authors, developers and designers. One common question asked is if we can create a marker interface or not and the answer is yes because of following reason: We can't create marker interface similar to Serializable or Cloneable but we can simulate the functionality by writing extra code around the custom marker interface.

One of my favorite subjects is real-time communication. A chat component is one of the most basic forms of real-time communication. In the past, I've blogged about how to create a JavaFX 1.3 based chat application using a Comet Server. Meanwhile, we updated the internal Chat Application we are using at LodgON and it is now using JavaFX 2 and RedFX 2. The most basic JavaFX Chat Application is described at http://redfx.org/samples/chat/index.html and the required binaries can also be downloaded from that site. The example shown on the RedFX samples page is very very basic and of course not very useful in real-world cases. However, the basics about sending and receiving messages, processing them and visualizing them, are very similar. We use the exact same principles for a more complex Chat Application for focus groups that we are currently migrating from JavaFX 1.3 to JavaFX 2.1. A Chat application requires a client component and a server component. If you look at the client code that can be downloaded from the RedFX.org download section, you'll probably agree that JavaFX is the perfect candidate platform for writing chat applications. Very few lines of code are needed, and any Java developer can easily extend this application. The server component, which can be downloaded here contains a Java EE 6 Web Archive. It includes the RedFX server components, a few configuration files, and it runs out of the box on Glassfish 3.1.2 (if you enable Comet and/or Web sockets -- those are disabled by default unfortunately). A couple of weeks ago, we made the beta-release of RedFX available in a binary form. It is our intention to make available all source code that is required to run the basic samples. However, this takes time. A couple of months ago, we open-sourced the DaliCore platform, and that takes time. Making a project open-source involves much much more than putting the code in a zip and make it available online. It is my goal to make the RedFX client part of the open-source JFXtras.org project. We still have to figure out how we will deal with dependencies, and how/where we can host the RedFX server components. We will do this as fast as we can, but there are only 25 hours in a day...

My prefered solution was to use the Maven ‘update snapshots’ command line argument.

Use short enough and long enough variable names in each scope of code. Generally length may be 1 char for loop counters, 1 word for condition/loop variables, 1-2 words for methods, 2-3 words for classes, 3-4 words for globals. Use specific names for variables, for example "value", "equals", "data", ... are not valid names for any case. Use meaningful names for variables. Variable name must define the exact explanation of its content. Don't start variables with o_, obj_, m_ etc. A variable does not need tags which states it is a variable. Obey company naming standards and write variable names consistently in application: e.g. txtUserName, lblUserName, cmbSchoolType, ... Otherwise readability will reduce and find/replace tools will be unusable. Obey programming language standards and don't use lowercase/uppercase characters inconsistently: e.g. userName, UserName, USER_NAME, m_userName, username, ... use Camel Case (aka Upper Camel Case) for classes: VelocityResponseWriter use Lower Case for packages: com.company.project.ui use Mixed Case (aka Lower Camel Case) for variables: studentName use Upper Case for constants : MAX_PARAMETER_COUNT = 100 use Camel Case for enum class names and Upper Case for enum values. don't use '_' anywhere except constants and enum values (which are constants). For example for Java, Don't reuse same variable name in the same class in different contexts: e.g. in method, constructor, class. So you can provide more simplicity for understandability and maintainability. Don't use same variable for different purposes in a method, conditional etc. Create a new and different named variable instead. This is also important for maintainability and readability. Don't use non-ASCII chars in variable names. Those may run on your platform but may not on others. Don't use too long variable names (e.g. 50 chars). Long names will bring ugly and hard-to-read code, also may not run on some compilers because of character limit. Decide and use one natural language for naming, e.g. using mixed English and German names will be inconsistent and unreadable. Use meaningful names for methods. The name must specify the exact action of the method and for most cases must start with a verb. (e.g. createPasswordHash) Obey company naming standards and write method names consistently in application: e.g. getTxtUserName(), getLblUserName(), isStudentApproved(), ... Otherwise readability will reduce and find/replace tools will be unusable. Obey programming language standards and don't use lowercase/uppercase characters inconsistently: e.g. getUserName, GetUserName, getusername, ... For example for Java, use Mixed Case for method names: getStudentSchoolType use Mixed Case for method parameters: setSchoolName(String schoolName) Use meaningful names for method parameters, so it can documentate itself in case of no documentation.

In a recent project, I had a requirement of connecting to multiple databases using hibernate. As tapestry-hibernate module does not provide an out-of-box support, I thought of adding one. https://github.com/tawus/tapestry5 Now that the application is in production, I thought of writing a simple “How to”. I have cloned the latest stable(5.3.2) tapestry project at https://github.com/tawus/tapestry5 and have added multiple database support to it. Single Database It is almost fully compatible with the previous integration when using a single database except for a few things 1) HibernateConfigurer has changed public interface HibernateConfigurer { /** * Passed the configuration so as to make changes. */ void configure(Configuration configuration); /** * Factory Id for which this configurer is meant for */ Class getMarker(); /** * Entity package names * * @return */ String[] getPackageNames(); } 2) There is no HibernateEntityPackageManager, as the packages can be contributed by adding more HibernateConfigurers with the same Markers. Multiple databases For multiple database, a marker has to be used for accessing Session or HibernateSessionManager @Inject @XDB private Session session; @Inject @YDB private HibernateSessionManager sessionManager; @XDB @CommitAfter void myMethod(){ } Also you have to define a HibernateSessionManager and a Session for the secondary database in the Module class. @Scope(ScopeConstants.PERTHREAD) @Marker(DatabaseTwo.class) public static HibernateSessionManager buildHibernateSessionManagerForFinacle( HibernateSessionSource sessionSource, PerthreadManager perthreadManager) { HibernateSessionManagerImpl service = new HibernateSessionManagerImpl(sessionSource, DatabaseTwo.class); perthreadManager.addThreadCleanupListener(service); return service; } @Marker(DatabaseTwo.class) public static Session buildSessionForFinacle( @Local HibernateSessionManager sessionManager, PropertyShadowBuilder propertyShadowBuilder) { return propertyShadowBuilder.build(sessionManager, "session", Session.class); } Notice an annotation @DatabaseTwo.class. This is a Factory marker and is used to identify a service related to a particular SessionFactory. @Retention(RetentionPolicy.RUNTIME) @Target( {ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD}) @FactoryMarker @Documented public @interface DatabaseTwo { } A typical AppModule for two databases will be public class AppModule { public static void bind(ServiceBinder binder) { binder.bind(DemoService.class, DemoServiceImpl.class); } @Contribute(HibernateSessionSource.class) public static void configureHibernateSources(OrderedConfiguration configurers) { configurers.add("databaseOne", new HibernateConfigurer() { public void configure(org.hibernate.cfg.Configuration configuration) { configuration.configure("/databaseOne.xml"); } public Class getMarker() { return DefaultFactory.class; } public String[] getPackageNames() { return new String[] {"org.example.demo.one"}; } }); configurers.add("databaseTwo", new HibernateConfigurer() { public void configure(org.hibernate.cfg.Configuration configuration) { configuration.configure("/databaseTwo.xml"); } public Class getMarker() { return DatabaseTwo.class; } public String[] getPackageNames() { return new String[] {"org.example.demo.two"}; } }); } @Contribute(SymbolProvider.class) @ApplicationDefaults public static void addSymbols(MappedConfiguration configuration) { configuration.add(HibernateSymbols.DEFAULT_CONFIGURATION, "false"); configuration.add("tapestry.app-package", "org.example.demo"); } @Scope(ScopeConstants.PERTHREAD) @Marker(DatabaseTwo.class) public static HibernateSessionManager buildHibernateSessionManagerForFinacle( HibernateSessionSource sessionSource, PerthreadManager perthreadManager) { HibernateSessionManagerImpl service = new HibernateSessionManagerImpl(sessionSource, DatabaseTwo.class); perthreadManager.addThreadCleanupListener(service); return service; } @Marker(DatabaseTwo.class) public static Session buildSessionForFinacle( @Local HibernateSessionManager sessionManager, PropertyShadowBuilder propertyShadowBuilder) { return propertyShadowBuilder.build(sessionManager, "session", Session.class); } } Injecting into Services You can inject a session in a service using the marker. As DatabaseOne is being used as the default configuration, in order to inject its Session, you have to annotate it with @DefaultFactory. For DatabaseTwo, you can use @DatabaseTwo annotation. public class DemoServiceImpl implements DemoService { private Session sessionOne; private Session sessionTwo; public DemoServiceImpl( @DefaultFactory Session sessionOne, @DatabaseTwo Session sessionTwo) { this.sessionOne = sessionOne; this.sessionTwo = sessionTwo; } @SuppressWarnings("unchecked") public List listOnes() { return sessionOne.createCriteria(EntityOne.class).list(); } @SuppressWarnings("unchecked") public List listTwos() { return sessionTwo.createCriteria(EntityTwo.class).list(); } public void save(EntityOne entityOne) { sessionOne.saveOrUpdate(entityOne); } public void save(EntityTwo entityTwo) { sessionTwo.saveOrUpdate(entityTwo); } } Using @CommitAfter You can add an advice the same way you used to. The only change is in @CommitAfter. You have to additionally annotate the method with the respective marker. public interface DemoService { List listOnes(); List listTwos(); @CommitAfter @DefaultFactory void save(EntityOne entityOne); @CommitAfter @DatabaseTwo void save(EntityTwo entityTwo); } Here is an example. From http://tawus.wordpress.com/2012/03/03/tapestry-hibernate-multiple-databases/

The JavaFX 2 class javafx.scene.paint.Color includes several fields that are static Color members. I have taken advantage of the convenience of these publicly available static fields in many of my JavaFX 2 examples shown in this blog. There is a lengthy list of these predefined Color fields ranging (in alphabetical order) from Color.ALICEBLUE to Color.YELLOWGREEN. I have sometimes thought it would be nice to quickly see what some of the less obvious colors look like and the simple JavaFX 2 application featured in this post provides a sampling of those colors. The sample JavaFX 2 application shown here uses simple Java reflection to introspect the JavaFX Color class for its public fields that themselves of type Color. The application then iterates over those public fields, providing information about each color such as the color's field name, a sample of the color, and the red/green/blue components of that color. The final row allows the user to specify red/green/blue values to see how such a color is rendered. This is useful if the user sees a standard color that is close to what he or she wants and the user wants to try adjusting it slightly. To ensure meaningful values for displaying a color based on provided red/green/blue values, the application ensures that entered values are treated as doubles between 0.0 and 1.0 even if they are not numbers or are numbers outside of that range. The simple JavaFX 2 application showing standard Color fields is shown in the next code listing. JavaFxColorDemo.java package dustin.examples; import static java.lang.System.err; import java.lang.reflect.Field; import javafx.application.Application; import javafx.event.EventHandler; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.control.*; import javafx.scene.input.MouseEvent; import javafx.scene.layout.HBox; import javafx.scene.layout.Pane; import javafx.scene.layout.VBox; import javafx.scene.paint.Color; import javafx.scene.shape.Rectangle; import javafx.scene.shape.RectangleBuilder; import javafx.stage.Stage; /** * Simple JavaFX 2 application that prints out values of standardly available * Color fields. * * @author Dustin */ public class JavaFxColorDemo extends Application { /** Width of label for colorn name. */ private final static int COLOR_NAME_WIDTH = 150; /** Width of rectangle that displays color. */ private final static int COLOR_RECT_WIDTH = 50; /** Height of rectangle that displays color. */ private final static int COLOR_RECT_HEIGHT = 25; private final TextField redField = TextFieldBuilder.create() .text("Red Value").build(); private final TextField greenField = TextFieldBuilder.create() .text("Green Value").build(); private final TextField blueField = TextFieldBuilder.create() .text("Blue Value").build(); private final Rectangle customColorRectangle = RectangleBuilder.create() .width(COLOR_RECT_WIDTH).height(COLOR_RECT_HEIGHT) .fill(Color.WHITE).stroke(Color.BLACK).build(); /** * Build a pane containing details about the instance of Color provided. * * @param color Instance of Color about which generated Pane should describe. * @return Pane representing information on provided Color instance. */ private Pane buildColorBox(final Color color, final String colorName) { final HBox colorBox = new HBox(); final Label colorNameLabel = new Label(colorName); colorNameLabel.setMinWidth(COLOR_NAME_WIDTH); colorBox.getChildren().add(colorNameLabel); final Rectangle colorRectangle = new Rectangle(COLOR_RECT_WIDTH, COLOR_RECT_HEIGHT); colorRectangle.setFill(color); colorRectangle.setStroke(Color.BLACK); colorBox.getChildren().add(colorRectangle); final String rgbString = String.valueOf(color.getRed()) + " / " + String.valueOf(color.getGreen()) + " / " + String.valueOf(color.getBlue()) + " // " + String.valueOf(color.getOpacity()); final Label rgbLabel = new Label(rgbString); rgbLabel.setTooltip(new Tooltip("Red / Green / Blue // Opacity")); colorBox.getChildren().add(rgbLabel); return colorBox; } /** * Extracts a double between 0.0 and 1.0 inclusive from the provided String. * * @param colorString String from which a double is extracted. * @return Double between 0.0 and 1.0 inclusive based on provided String; * will be 0.0 if provided String cannot be parsed. */ private double extractValidColor(final String colorString) { double colorValue = 0.0; try { colorValue = Double.valueOf(colorString); } catch (Exception exception) { colorValue = 0.0; err.println("Treating '" + colorString + "' as " + colorValue); } finally { if (colorValue < 0) { colorValue = 0.0; err.println("Treating '" + colorString + "' as " + colorValue); } else if (colorValue > 1) { colorValue = 1.0; err.println("Treating '" + colorString + "' as " + colorValue); } } return colorValue; } /** * Build pane with ability to specify own RGB values and see color. * * @return Pane with ability to specify colors. */ private Pane buildCustomColorPane() { final HBox customBox = new HBox(); final Button button = new Button("Display Color"); button.setPrefWidth(COLOR_NAME_WIDTH); button.setOnMouseClicked(new EventHandler() { @Override public void handle(MouseEvent t) { final Color customColor = new Color(extractValidColor(redField.getText()), extractValidColor(greenField.getText()), extractValidColor(blueField.getText()), 1.0); customColorRectangle.setFill(customColor); } }); customBox.getChildren().add(button); customBox.getChildren().add(this.customColorRectangle); customBox.getChildren().add(this.redField); customBox.getChildren().add(this.greenField); customBox.getChildren().add(this.blueField); return customBox; } /** * Build the main pane indicating JavaFX 2's pre-defined Color instances. * * @return Pane containing JavaFX 2's pre-defined Color instances. */ private Pane buildColorsPane() { final VBox colorsPane = new VBox(); final Field[] fields = Color.class.getFields(); // only want public for (final Field field : fields) { if (field.getType() == Color.class) { try { final Color color = (Color) field.get(null); final String colorName = field.getName(); colorsPane.getChildren().add(buildColorBox(color, colorName)); } catch (IllegalAccessException illegalAccessEx) { err.println( "Securty Manager does not allow access of field '" + field.getName() + "'."); } } } colorsPane.getChildren().add(buildCustomColorPane()); return colorsPane; } /** * Start method overridden from parent Application class. * * @param stage Primary stage. * @throws Exception JavaFX application exception. */ @Override public void start(final Stage stage) throws Exception { final Group rootGroup = new Group(); final Scene scene = new Scene(rootGroup, 700, 725, Color.WHITE); final ScrollPane scrollPane = new ScrollPane(); scrollPane.setPrefWidth(scene.getWidth()); scrollPane.setPrefHeight(scene.getHeight()); scrollPane.setContent(buildColorsPane()); rootGroup.getChildren().add(scrollPane); stage.setScene(scene); stage.setTitle("JavaFX Standard Colors Demonstration"); stage.show(); } /** * Main function for running JavaFX application. * * @param arguments Command-line arguments; none expected. */ public static void main(final String[] arguments) { Application.launch(arguments); } } The snapshots shown next demonstrate this simple application. The first snapshot shows the application after loading. The second snapshot shows the application after scrolling down to the bottom and demonstrates use of the Tooltip and of the TextField.setPrompt(String) method. The third image shows the results of providing red/green/blue values and clicking on the button to see the corresponding color. The simple JavaFX 2 application shown in this post makes it easy to get an idea of what colors are available as standard JavaFX 2 public static Color fields. It also allows one to enter red/green/blue values that might be provided to the Color constructor to obtain an instance of Color. From http://marxsoftware.blogspot.com/2012/02/viewing-javafx-2-standard-colors.html

Java Collections allows you to add one or more elements with the same key by using the MultiValueMap class, found in the Apache org.apache.commons.collections package (http://commons.apache.org/collections/): package multihashmap.example; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set; import org.apache.commons.collections.map.MultiValueMap; public class MultiHashMapExample { public static void main(String[] args) { List list; MultiValueMap map = new MultiValueMap(); map.put("A", 4); map.put("A", 6); map.put("B", 7); map.put("C", 1); map.put("B", 9); map.put("A", 5); Set entrySet = map.entrySet(); Iterator it = entrySet.iterator(); System.out.println(" Object key Object value"); while (it.hasNext()) { Map.Entry mapEntry = (Map.Entry) it.next(); list = (List) map.get(mapEntry.getKey()); for (int j = 0; j < list.size(); j++) { System.out.println("\t" + mapEntry.getKey() + "\t " + list.get(j)); } } } } Since Java Core does’t come with some solutions for supporting multiple keys, using the org.apache.commons.collections seems to be a proper way to deal with multiple keys. And the output is: From http://e-blog-java.blogspot.com/2012/02/how-to-allow-duplicate-key-in-java.html

for a while now, we had been operating in the wild west when it comes to building our applications and deploying to production. builds were typically done straight from the developer’s ide and manually deployed to one of our app servers. we had a manual process in place, where the developer would do the following steps. check all project code into subversion and tag build the application. archive the application binary to a network drive deploy to production update our deployment wiki with the date and version number of the app that was just deployed. the problem is that there were occasionally times where one of these steps were missed, and it always seemed to be at a time when we needed to either rollback to the previous version, or branch from the tag to do a bugfix. sometimes the previous version had not been archived to the network, or the developer forgot to tag svn. we were already using jenkins to perform automated builds, so we wanted to look at extending it further to perform release builds. the maven release plug-in provides a good starting point for creating an automated release process. we have also just started using the nexus maven repository and wanted to incorporate that as well to archive our binaries to, rather than archiving them to a network drive. the first step is to set up the project’s pom file with the deploy plugin as well as include configuration information about our nexus and subversion repositories. org.apache.maven.plugins maven-release-plugin 2.2.2 http://mks:8080/svn/jrepo/tags/frameworks/siestaframework the release plugin configuration is pretty straightforward. the configuration takes the subversion url of the location where the tags will reside for this project. the next step is to configure the svn location where the code will be checked out from. scm:svn:http://mks:8080/svn/jrepo/trunk/frameworks/siestaframework http://mks:8080/svn the last step in configuring the project is to set up the location where the binaries will be archived to. in our case, the nexus repository. lynden-java-release lynden release repository http://cisunwk:8081/nexus/content/repositories/lynden-java-release the project is now ready to use the maven release plug-in. the release plugin provides a number of useful goals. release:clean – cleans the workspace in the event the last release process was not successful. release: prepare – performs a number of operations checks to make sure that there are no uncommitted changes. ensures that there are no snapshot dependencies in the pom file, changes the version of the application and removes snapshot from the version. ie 1.0.3-snapshot becomes 1.0.3 run project tests against modified poms commit the modified pom tag the code in subersion increment the version number and append snapshot. ie 1.0.3 becomes 1.0.4-snapshot commit modified pom release: perform – performs the release process checks out the code using the previously defined tag runs the deploy maven goal to move the resulting binary to the repository. putting it all together the last step in this process is to configure jenkins to allow release builds on-demand, meaning we want the user to have to explicitly kick off a release build for this process to take place. we have download and installed the release jenkins plug-in in order to allow developers to kick off release builds from jenkins. the release plug-in will execute tasks after the normal build has finished. below is a screenshot of the configuration of one of our projects. the release build option for the project is enabled by selecting the “configure release build” option in the “build environment” section. the maven release plug-in is activated by adding the goals to the “after successful release build” section. (the –b option enables batch mode so that the release plug-in will not ask the user for input, but use defaults instead.) once the release option has been configured for a project there will be a “release” icon on the left navigation menu for the project. selecting this will kick off a build and then the maven release process, assuming the build succeeds. finally a look at svn and nexus verifies that the build for version 1.0.4 of the siesta-framework project has been tagged in svn and uploaded to nexus. the next steps for this project will be to generate release notes for release builds, and also to automate a deployment pipeline, so that developers can deploy to our test, staging and production servers via jenkins rather than manually from their development workstations. twitter: @robterp blog: http://rterp.wordpress.com

There is an increasing number of libraries which are described as high performance and have benchmarks to back that claim up. Here is a selection that I am aware of.

I recently spent some time learning JavaFX and doing a custom control is a good practice to dive a little bit deeper into the concepts of a new gui library. Having some background in financial software I did of course miss the equivalent of a JFormattedTextField and a JSpinner control in the current 2.0 release. So going down that road seemed like a good choice to me. And here are my controls: a NumberTextField, that can be configured with an arbitrary NumberFormat a Spinner field that also can also be configured with an arbitrary NumberFormat and controlled with the arrow keys or arrow buttons, that are part of the control The controls and an example can be downloaded as a netbeans project.The example also includes a css file that styles the spinner with either straight or rounded corners. NumberTextField The NumberTextField was pretty easy and I wouldn't even consider this a custom control as I only changed the behaviour of an already existing control. It extends a normal TextField, adds a NumberProperty that serves as the model and holds a BigDecimal (for financial applications we need exact types) and does some formatting and parsing.That's it, no big deal. package de.thomasbolz.javafx; import java.math.BigDecimal; import java.text.NumberFormat; import java.text.ParseException; import javafx.beans.property.ObjectProperty; import javafx.beans.property.SimpleObjectProperty; import javafx.beans.value.ChangeListener; import javafx.beans.value.ObservableValue; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.scene.control.TextField; /** * Textfield implementation that accepts formatted number and stores them in a * BigDecimal property The user input is formatted when the focus is lost or the * user hits RETURN. * * @author Thomas Bolz */ public class NumberTextField extends TextField { private final NumberFormat nf; private ObjectProperty number = new SimpleObjectProperty<>(); public final BigDecimal getNumber() { return number.get(); } public final void setNumber(BigDecimal value) { number.set(value); } public ObjectProperty numberProperty() { return number; } public NumberTextField() { this(BigDecimal.ZERO); } public NumberTextField(BigDecimal value) { this(value, NumberFormat.getInstance()); initHandlers(); } public NumberTextField(BigDecimal value, NumberFormat nf) { super(); this.nf = nf; initHandlers(); setNumber(value); } private void initHandlers() { // try to parse when focus is lost or RETURN is hit setOnAction(new EventHandler() { @Override public void handle(ActionEvent arg0) { parseAndFormatInput(); } }); focusedProperty().addListener(new ChangeListener() { @Override public void changed(ObservableValue observable, Boolean oldValue, Boolean newValue) { if (!newValue.booleanValue()) { parseAndFormatInput(); } } }); // Set text in field if BigDecimal property is changed from outside. numberProperty().addListener(new ChangeListener() { @Override public void changed(ObservableValue obserable, BigDecimal oldValue, BigDecimal newValue) { setText(nf.format(newValue)); } }); } /** * Tries to parse the user input to a number according to the provided * NumberFormat */ private void parseAndFormatInput() { try { String input = getText(); if (input == null || input.length() == 0) { return; } Number parsedNumber = nf.parse(input); BigDecimal newValue = new BigDecimal(parsedNumber.toString()); setNumber(newValue); selectAll(); } catch (ParseException ex) { // If parsing fails keep old number setText(nf.format(number.get())); } } } NumberSpinner The NumberSpinner is only slightly more complicated. It builds upon the NumberTextField and adds an increment and decrement button, that increments and decrements the value in the field by a stepwidth. Initial value, stepwidth and underlying NumberFormat are set in the constructor. The textfield and the size of the buttons are scaled according to the font size that can be - for example - set in the .css file. package de.thomasbolz.javafx; import java.math.BigDecimal; import java.text.NumberFormat; import javafx.beans.binding.NumberBinding; import javafx.beans.property.ObjectProperty; import javafx.beans.property.SimpleObjectProperty; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.geometry.Pos; import javafx.scene.control.Button; import javafx.scene.input.KeyCode; import javafx.scene.input.KeyEvent; import javafx.scene.layout.HBox; import javafx.scene.layout.StackPane; import javafx.scene.layout.VBox; import javafx.scene.shape.LineTo; import javafx.scene.shape.MoveTo; import javafx.scene.shape.Path; import javax.swing.JSpinner; /** * JavaFX Control that behaves like a {@link JSpinner} known in Swing. The * number in the textfield can be incremented or decremented by a configurable * stepWidth using the arrow buttons in the control or the up and down arrow * keys. * * @author Thomas Bolz */ public class NumberSpinner extends HBox { public static final String ARROW = "NumberSpinnerArrow"; public static final String NUMBER_FIELD = "NumberField"; public static final String NUMBER_SPINNER = "NumberSpinner"; public static final String SPINNER_BUTTON_UP = "SpinnerButtonUp"; public static final String SPINNER_BUTTON_DOWN = "SpinnerButtonDown"; private final String BUTTONS_BOX = "ButtonsBox"; private NumberTextField numberField; private ObjectProperty stepWitdhProperty = new SimpleObjectProperty<>(); private final double ARROW_SIZE = 4; private final Button incrementButton; private final Button decrementButton; private final NumberBinding buttonHeight; private final NumberBinding spacing; public NumberSpinner() { this(BigDecimal.ZERO, BigDecimal.ONE); } public NumberSpinner(BigDecimal value, BigDecimal stepWidth) { this(value, stepWidth, NumberFormat.getInstance()); } public NumberSpinner(BigDecimal value, BigDecimal stepWidth, NumberFormat nf) { super(); this.setId(NUMBER_SPINNER); this.stepWitdhProperty.set(stepWidth); // TextField numberField = new NumberTextField(value, nf); numberField.setId(NUMBER_FIELD); // Enable arrow keys for dec/inc numberField.addEventFilter(KeyEvent.KEY_PRESSED, new EventHandler() { @Override public void handle(KeyEvent keyEvent) { if (keyEvent.getCode() == KeyCode.DOWN) { decrement(); keyEvent.consume(); } if (keyEvent.getCode() == KeyCode.UP) { increment(); keyEvent.consume(); } } }); // Painting the up and down arrows Path arrowUp = new Path(); arrowUp.setId(ARROW); arrowUp.getElements().addAll(new MoveTo(-ARROW_SIZE, 0), new LineTo(ARROW_SIZE, 0), new LineTo(0, -ARROW_SIZE), new LineTo(-ARROW_SIZE, 0)); // mouse clicks should be forwarded to the underlying button arrowUp.setMouseTransparent(true); Path arrowDown = new Path(); arrowDown.setId(ARROW); arrowDown.getElements().addAll(new MoveTo(-ARROW_SIZE, 0), new LineTo(ARROW_SIZE, 0), new LineTo(0, ARROW_SIZE), new LineTo(-ARROW_SIZE, 0)); arrowDown.setMouseTransparent(true); // the spinner buttons scale with the textfield size // TODO: the following approach leads to the desired result, but it is // not fully understood why and obviously it is not quite elegant buttonHeight = numberField.heightProperty().subtract(3).divide(2); // give unused space in the buttons VBox to the incrementBUtton spacing = numberField.heightProperty().subtract(2).subtract(buttonHeight.multiply(2)); // inc/dec buttons VBox buttons = new VBox(); buttons.setId(BUTTONS_BOX); incrementButton = new Button(); incrementButton.setId(SPINNER_BUTTON_UP); incrementButton.prefWidthProperty().bind(numberField.heightProperty()); incrementButton.minWidthProperty().bind(numberField.heightProperty()); incrementButton.maxHeightProperty().bind(buttonHeight.add(spacing)); incrementButton.prefHeightProperty().bind(buttonHeight.add(spacing)); incrementButton.minHeightProperty().bind(buttonHeight.add(spacing)); incrementButton.setFocusTraversable(false); incrementButton.setOnAction(new EventHandler() { @Override public void handle(ActionEvent ae) { increment(); ae.consume(); } }); // Paint arrow path on button using a StackPane StackPane incPane = new StackPane(); incPane.getChildren().addAll(incrementButton, arrowUp); incPane.setAlignment(Pos.CENTER); decrementButton = new Button(); decrementButton.setId(SPINNER_BUTTON_DOWN); decrementButton.prefWidthProperty().bind(numberField.heightProperty()); decrementButton.minWidthProperty().bind(numberField.heightProperty()); decrementButton.maxHeightProperty().bind(buttonHeight); decrementButton.prefHeightProperty().bind(buttonHeight); decrementButton.minHeightProperty().bind(buttonHeight); decrementButton.setFocusTraversable(false); decrementButton.setOnAction(new EventHandler() { @Override public void handle(ActionEvent ae) { decrement(); ae.consume(); } }); StackPane decPane = new StackPane(); decPane.getChildren().addAll(decrementButton, arrowDown); decPane.setAlignment(Pos.CENTER); buttons.getChildren().addAll(incPane, decPane); this.getChildren().addAll(numberField, buttons); } /** * increment number value by stepWidth */ private void increment() { BigDecimal value = numberField.getNumber(); value = value.add(stepWitdhProperty.get()); numberField.setNumber(value); } /** * decrement number value by stepWidth */ private void decrement() { BigDecimal value = numberField.getNumber(); value = value.subtract(stepWitdhProperty.get()); numberField.setNumber(value); } public final void setNumber(BigDecimal value) { numberField.setNumber(value); } public ObjectProperty numberProperty() { return numberField.numberProperty(); } public final BigDecimal getNumber() { return numberField.getNumber(); } // debugging layout bounds public void dumpSizes() { System.out.println("numberField (layout)=" + numberField.getLayoutBounds()); System.out.println("buttonInc (layout)=" + incrementButton.getLayoutBounds()); System.out.println("buttonDec (layout)=" + decrementButton.getLayoutBounds()); System.out.println("binding=" + buttonHeight.toString()); System.out.println("spacing=" + spacing.toString()); } } number_spinner.css Last but not least the control can be styled in the css file. I played around with two looks, rounded corners and straight corners (see attached screenshots). You can switch between them by changing the border/background-radiuses in #NumberField, #ButtonBox, #SpinnerButtonUp and #SpinnerButtonDown. .root{ -fx-font-size: 24pt; /* -fx-base: rgb(255,0,0);*/ /* -fx-background: rgb(50,50,50);*/ } #NumberField { -fx-border-width: 1; -fx-border-color: lightgray; -fx-background-insets:1; -fx-border-radius:3 0 0 3; /* -fx-border-radius:0 0 0 0;*/ } #NumberSpinnerArrow { -fx-fill: gray; -fx-stroke: gray; /* -fx-effect: innershadow( gaussian , black , 2 , 0.6 , 1 , 1 )*/ } #ButtonsBox { -fx-border-color:lightgray; -fx-border-width: 1 1 1 0; -fx-border-radius: 0 3 3 0; /* -fx-border-radius: 0 0 0 0;*/ } #SpinnerButtonUp { -fx-background-insets: 0; -fx-background-radius:0 3 0 0; /* -fx-background-radius:0;*/ } #SpinnerButtonDown { -fx-background-insets: 0; -fx-background-radius:0 0 3 0; /* -fx-background-radius:0;*/ } Conclusion Doing custom controls in JavaFX is really no big deal although the examples above are really easy ones. JavaFX being a pure Java API since 2.0 now integrates even better than before with languages like groovy where BigDecimal is a first class citizen. This makes it an almost perfect couple for financial desktops applications.

Execute the slow integration tests separately from unit tests and show as much information about them as possible in Sonar.

Right now, when I try to persist an object in Google App Engine, I’m facing the error “Java.lang.VerifyError: Expecting a stackmap frame at branch target“. I’m using JDK 7 and it seems like the problem lies with this JDK. After googling a bit, I found that there seems to be two solutions to fix this problem. Solution 1: Change to JDK 6 As simple as is, change your JDK to version 6 and you won’t be bugged by this exception anymore. Well, in my case, I have to use JDK 7. So, moving on to the solution 2. Solution 2: Configure JVM Go to Windows -> Preferences -> Installed JREs. Select the default JVM and click edit. Then add this parameter as VM argument “-XX:-UseSplitVerifier” as seen below. This should solve the issue. From http://veerasundar.com/blog/2012/01/java-lang-verifyerror-expecting-a-stackmap-frame-at-branch-target-jdk-7/

i want to share something a software developer or operations guy every now and then encounters. and which i did yesterday. it all started with our nightly maven build failing last saturday jan 28 on a java.lang.noclassdeffounderror: javax/xml/bind/validationeventlocator the interesting snippet from the concole output from this build looked like this: [info] [jaxb2:generate {execution: xxx-schema-gen}] [fatal error] org.jvnet.mjiip.v_2.xjc2mojo#execute() caused a linkage error (java.lang.noclassdeffounderror) and may be out-of-date. check the realms: [fatal error] plugin realm = app0.child-container[org.jvnet.jaxb2.maven2:maven-jaxb2-plugin] urls[0] = file:/home/hudson/.m2/repository/org/jvnet/jaxb2/maven2/maven-jaxb2-plugin/0.8.1/maven-jaxb2-plugin-0.8.1.jar urls[1] = file:/home/hudson/.m2/repository/org/jvnet/jaxb2/maven2/maven-jaxb2-plugin-core/0.8.1/maven-jaxb2-plugin-core-0.8.1.jar urls[2] = file:/home/hudson/.m2/repository/com/sun/org/apache/xml/internal/resolver/20050927/resolver-20050927.jar urls[3] = file:/home/hudson/.m2/repository/org/sonatype/plexus/plexus-build-api/0.0.7/plexus-build-api-0.0.7.jar urls[4] = file:/home/hudson/.m2/repository/org/codehaus/plexus/plexus-utils/1.5.15/plexus-utils-1.5.15.jar urls[5] = file:/home/hudson/.m2/repository/org/jfrog/maven/annomojo/maven-plugin-anno/1.3.1/maven-plugin-anno-1.3.1.jar urls[6] = file:/home/hudson/.m2/repository/org/jvnet/jaxb2/maven2/maven-jaxb22-plugin/0.8.1/maven-jaxb22-plugin-0.8.1.jar urls[7] = file:/home/hudson/.m2/repository/com/sun/xml/bind/jaxb-impl/2.2.5-b10/jaxb-impl-2.2.5-b10.jar urls[8] = file:/home/hudson/.m2/repository/com/sun/xml/bind/jaxb-xjc/2.2.5-b10/jaxb-xjc-2.2.5-b10.jar [fatal error] container realm = plexus.core.maven [info] ------------------------------------------------------------------------ [error] fatal error [info] ------------------------------------------------------------------------ [info] javax/xml/bind/validationeventlocator [info] ------------------------------------------------------------------------ [info] trace java.lang.noclassdeffounderror: javax/xml/bind/validationeventlocator at com.sun.tools.xjc.reader.internalizer.domforestscanner.scan(domforestscanner.java:84) it seems that the maven-jaxb2-plugin –we use for jaxb to generate java sources for a certain schema–suddenly triggers a (missing or incompatible?) dependency. the weird thing is the “suddenly” part, since the last commit was done on friday after which the normal continuous builds ran fine and the even the nightly build on midnight friday to saturday. we use maven to take care of these things right? always have a known set of dependencies, each part of the process? ofcourse at the time things didn’t seem so obvious. first thing i wondered, could it have something do to with a java 5 vs 6 problem? as a matter of fact, on our project we’re trying to go to java 6 after a long time, but i’m the only one which already upgraded my local developer machine to work with jdk6 for a while and see if nothing strange happens. you know, keeping a lot of files from your workspace in a special “do not commit” working set or hidden from view, in order to prevent it from prematurely ending up in version control so naturally, i first explored all changesets leading up to the failed build to see if i by accident committed a file i shouldn’t have. but i couldn’t find anything. next i thought: could hudson be configured incorrectly last week by a parting co-worker (which had a somewhat unofficial ownership of our ci infrastructure until he left) which now surfaced, because e.g. a server was restarted or hudson was upgraded? checked a few things out: our hudson startup.sh looked like /usr/java/latest/bin/java -jar hudson.war --httpport=9090 --ajp13port=9091 --deamon --logfile=hudson.log & where /usr/java/latest/bin/java pointed to “java(tm) se runtime environment (build 1.6.0 _24-b07)” while normal “java” on the command-line pointed to “java(tm) 2 runtime environment, standard edition (build 1.5.0 _22-b03)” . could it be that the “latest” directory pointed earlier to java 5 en (by some mysterious upgrade on the server) now suddenly links to java 6. could the java version we start hudson with affect the java version we use for our hudson jobs? i don’t hope so! consequently, i checked the hudson configuration itself: what kind of jdk’s did we configure? luckily, only one: named “1_5_0″ with java_home pointing to “/usr/java/default”. but again not clear from the path to what java version it points, until i figured out this symlink leads to “/usr/java/jdk1.5.0_22″. good, jdk 5 should be used as default for all our maven builds. to verify i added a 2nd bogus jdk entry in the hudson configuration, so i was able to explicitly choose it in the job configuration – and after triggering a new build i was sure hudson was configured correctly jdk-wise. man, how one can digress! so let’s take a look at the offending library at hand. from the stacktrace one can spot the maven-jaxb2-plugin artefact from the group org.jvnet.jaxb2.maven2 . did something happen to this dependency itself? i opened up our nexus console, searched for it and saw the screen below: wait a minute! why do we have two versions of this plugin? in nexus i opened up the tab artefact information on the 0.8.1 version and saw that the uploaded date listed last saturday 28th of jan. i know we shouldn’t have more than one version of this plugin in nexus. did a small check on the jira release notes page of this plugin… well then. so a new release of the plugin was published online last saturday and the nightly build triggered the download of a new version 0.8.1 – which seemed to be compiled against java 6 now which caused the java.lang.noclassdeffounderror . this naturally lead me to the offending part in our pom.xml : org.jvnet.jaxb2.maven2 maven-jaxb2-plugin argh. no version! changed it into: org.jvnet.jaxb2.maven2 maven-jaxb2-plugin 0.8.0 i committed the pom.xml and triggerd a manual build – and… it worked. ofcourse. in conclusion there are some lessons to be learned i think: when debugging a problem, always try to reason about possible paths which come to mind to follow first and don’t get hung on your very first idea which pops up. this got me i think sidetracked too long on finding out whether or not i accidentally committed java 6 files or whether or not hudson got accidentally misconfigured into not using java 5 anymore somehow. troubleshooting skills are highly dependent of previous experience in a field and ofcourse, if ever a similar problem arises i’d be able to recognize it faster now. write it down – so a collegue or yourself can find it back more easily later on. explicity set dependency versions in your pom.xml! don’t blame maven for everything does anyone else have a troubleshooting-tale of going in the wrong direction? original posting: http://tedvinke.wordpress.com/2012/02/01/why-does-my-maven-build-fail

We all know the Java platform allows us to create reusable objects in memory. However, all of those objects exist only as long as the Java virtual machine remains running. It would be nice if the objects we create could exist beyond the lifetime of the virtual machine. Well, with object serialization, you can flatten your objects and reuse them in powerful ways. Object serialization is the process of saving an object’s state to a sequence of bytes, as well as the process of rebuilding those bytes into a live object at some future time. The Java Serialization API provides a standard mechanism for developers to handle object serialization. The API is small and easy to use, provided the classes and methods are understood. By implementating java.io.Serializable, you get “automatic” serialization capability for objects of your class. No need to implement any other logic, it’ll just work. The Java runtime will use reflection to figure out how to marshal and unmarshal your objects. In earlier version of Java, reflection was very slow, and so serializaing large object graphs (e.g. in client-server RMI applications) was a bit of a performance problem. To handle this situation, the java.io.Externalizable interface was provided, which is like java.io.Serializable but with custom-written mechanisms to perform the marshalling and unmarshalling functions (you need to implement readExternal and writeExternal methods on your class). This gives you the means to get around the reflection performance bottleneck. In recent versions of Java (1.3 onwards, certainly) the performance of reflection is vastly better than it used to be, and so this is much less of a problem. I suspect you’d be hard-pressed to get a meaningful benefit from Externalizable with a modern JVM. Also, the built-in Java serialization mechanism isn’t the only one, you can get third-party replacements, such as JBoss Serialization, which is considerably quicker, and is a drop-in replacement for the default. A big downside of Externalizable is that you have to maintain this logic yourself – if you add, remove or change a field in your class, you have to change your writeExternal/readExternal methods to account for it. In summary, Externalizable is a relic of the Java 1.1 days. There’s really no need for it any more. References http://java.sun.com/developer/technicalArticles/Programming/serialization http://docs.oracle.com/javase/6/docs/api/java/io/Serializable.html http://docs.oracle.com/javase/6/docs/api/java/io/Externalizable.html From http://singztechmusings.in/marshalling-unmarshalling-java-objects-serialization-vs-externalization/

WADL (Web Application Description Language) is to REST what WSDL is to SOAP. The mere existence of this language causes a lot of controversy (see: Do we need WADL? and To WADL or not to WADL). I can think of few legitimate use cases for using WADL, but if you are here already, you are probably not seeking for yet another discussion. So let us move forward to the WADL itself. In principle WADL is similar to WSDL, but the structure of the language is much different. Whilst WSDL defines a flat list of messages and operations either consuming or producing some of them, WADL emphasizes the hierarchical nature of RESTful web services. In REST, the primary artifact is the resource. Each resource (noun) is represented as an URI. Every resource can define both CRUD operations (verbs, implemented as HTTP methods) and nested resources. The nested resource has a strong relationship with a parent resource, typically representing an ownership. A simple example would be http://example.com/api/books resource representing a list of books. You can (HTTP) GET this resource, meaning to retrieve the whole list. You can also GET the http://example.com/api/books/7 resource, fetching the details of 7th book inside books resource. Or you can even PUT new version or DELETE the resource altogether using the same URI. You are not limited to a single level of nesting: GETting http://example.com/api/books/7/reviews?page=2&size=10 will retrieve the second page (up to 10 items) of reviews of 7th book. Obviously you can also place other resources next to books, like http://example.com/api/readers The requirement arose to formally and precisely describe every available resource, method, request and response, just like WSDL guys were able to do. WADL is one of the options to describe “available URIs", although some believe that well-written REST service should be self-descriptive (see HATEOAS). Nevertheless here is a simple, empty WADL document: Nothing fancy here. Note that the tag defines base API address. All named resources, which we are just about to add, are relative to this address. Also you can define several tags to describe more than one APIs. So, let's add a simple resource: This defines resource under http://example.com/api/books with two methods possible: GET to retrieve the whole list and POST to create (add) new item. Depending on your requirements you might want to allow DELETE method as well (to delete all items), and it is the responsibility of WADL to document what is allowed. Remember our example at the beginning: /books/7? Obviously 7 is just an example and we won't declare every possible book id in WADL. Instead there is a handy placeholder syntax:There are two important aspects you should note: first, The {bookId} place-holder was used in place of nested resource. Secondly, to make it clear, we are documenting this place-holder using tag. We will see soon how it can be used in combination with methods. Just to make sure you are still with me, the document above describes GET /books and GET /books/some_id resources. The web service is getting complex, however it describes quite a lot of operations. First of all GET /books/42/reviews is a valid operation. But the interesting part is the nested tag. As you can see we can describe parameters of each method independently. In our case optional query parameters (as opposed to template parameters used previously for URI place-holders) were defined. This gives the client additional knowledge about acceptable page and size query parameters. This means that /books/7/reviews?page=2&size=10 is a valid resource identifier. And did I mention that every resource, method and parameter can have documentation attached as per the WADL specification? We will stop here and only mention about remaining pieces of WADL. First of all, as you have probably guessed so far, there is also a child tag possible for each . Both request and response can define exact grammar (e.g. in XML Schema) that either the request or the response must follow. The response can also document possible HTTP response codes. But since we will be using the knowledge you have gained so far in a code-first application, I intentionally left the definition. WADL is agile and it allows you to define as little (or as much) information as you need. So we know the basics of WADL, now we would like to use it, maybe as a consumer or as a producer in a Java-based application. Fortunately there is a wadl.xsd XML Schema description of the language itself, which we can use to generate JAXB-annotated POJOs to work with (using xjc tool in the JDK): $ wget http://www.w3.org/Submission/wadl/wadl.xsd $ xjc wadl.xsd And there it... hangs! The life of a software developer is full of challenges and non-trivial problems. And sometimes it is just an annoying network filter that makes suspicious packets (together with half hour of your life) disappear. It is not hard to spot the problem, once you recall that article written around 2008: W3C’s Excessive DTD Traffic: Accessing xml.xsd from the browser returns an HTML page instantly, but xjc tool waits forever. Downloading this file locally and correcting the schemaLocation attribute in wadl.xsd helped. It's always the little things... $ xjc wadl.xsd parsing a schema... compiling a schema... net/java/dev/wadl/_2009/_02/Application.java net/java/dev/wadl/_2009/_02/Doc.java net/java/dev/wadl/_2009/_02/Grammars.java net/java/dev/wadl/_2009/_02/HTTPMethods.java net/java/dev/wadl/_2009/_02/Include.java net/java/dev/wadl/_2009/_02/Link.java net/java/dev/wadl/_2009/_02/Method.java net/java/dev/wadl/_2009/_02/ObjectFactory.java net/java/dev/wadl/_2009/_02/Option.java net/java/dev/wadl/_2009/_02/Param.java net/java/dev/wadl/_2009/_02/ParamStyle.java net/java/dev/wadl/_2009/_02/Representation.java net/java/dev/wadl/_2009/_02/Request.java net/java/dev/wadl/_2009/_02/Resource.java net/java/dev/wadl/_2009/_02/ResourceType.java net/java/dev/wadl/_2009/_02/Resources.java net/java/dev/wadl/_2009/_02/Response.java net/java/dev/wadl/_2009/_02/package-info.java Since we'll be using these classes in a maven based project (and I hate committing generated classes to source repository), let's move xjc execution to maven lifecycle: org.codehaus.mojo jaxb2-maven-plugin 1.3 net.java.dev.jaxb2-commons jaxb-fluent-api 2.0.1 com.sun.xml jaxb-xjc xjc -Xfluent-api bindings.xjb net.java.dev.wadl Well, pom.xml isn't the most concise format ever... Never mind, this will generate WADL XML classes during every build, before the source code is compiled. I also love the fluent-api plugin that adds with*() methods along with ordinary setters, returning this to allow chaining. Pretty convenient. Finally we define more pleasant package name for generated artifacts (if you find net.java.dev.wadl._2009._02 package name pleasant enough, you can skip this step) and add Wadl prefix to all generated classes bindings.xjb file: We are now ready to produce and consume WADL in XML format using JAXB and POJO classes. Equipped with that knowledge and the foundation we are ready to develop some interesting library – which will be the subject of the next article. From http://nurkiewicz.blogspot.com/2012/01/gentle-introduction-to-wadl-in-java.html

I have been inserting log4j entries into a mongodb database and each entry has been given an ISODate timestamp: "timestamp" : ISODate("2012-01-17T22:30:19.839Z") To create a mapping for this, I had to manually add the timestamp as Spring Roo did not allow timestamp to be used as it was a reserved word. So I manually added: @DateTimeFormat(style="MM/dd/yyyy") private java.util.Date timestamp; But I started getting the following error: Invalid style specification: MM/dd/yyyy The stack trace for that error was: org.joda.time.format.DateTimeFormat.createFormatterForStyle(DateTimeFormat.java:702) org.joda.time.format.DateTimeFormat.patternForStyle(DateTimeFormat.java:212) com.comcast.uivr.web.LoggingController_Roo_Controller.ajc$interMethod$com_comcast_uivr_web_LoggingController_Roo_Controller$com_comcast_uivr_web_LoggingController$addDateTimeFormatPatterns(LoggingController_Roo_Controller.aj:98) com.comcast.uivr.web.LoggingController.ajc$interMethodDispatch2$com_comcast_uivr_web$addDateTimeFormatPatterns(LoggingController.java:1) com.comcast.uivr.web.LoggingController_Roo_Controller.ajc$interMethodDispatch1$com_comcast_uivr_web_LoggingController_Roo_Controller$com_comcast_uivr_web_LoggingController$addDateTimeFormatPatterns(LoggingController_Roo_Controller.aj) com.comcast.uivr.web.LoggingController_Roo_Controller.ajc$interMethod$com_comcast_uivr_web_LoggingController_Roo_Controller$com_comcast_uivr_web_LoggingController$list(LoggingController_Roo_Controller.aj:66) com.comcast.uivr.web.LoggingController.list(LoggingController.java:1) sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:597) org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212) org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126) org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617) org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578) org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778) javax.servlet.http.HttpServlet.service(HttpServlet.java:617) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) java.lang.Thread.run(Thread.java:662) To fix this I attempted to add the ISO date format for the @DateTimeFormat @DateTimeFormat(style="yyyyMMdd'T'HHmmss.SSSZ") private java.util.Date timestamp; Which still did not work and had the error. To resolve this I shitched to use ISO.DATE_TIME as the style: @DateTimeFormat(iso=ISO.DATE_TIME) private java.util.Date timestamp; From http://www.baselogic.com/blog/development/springframework/mapping-mongodb-isodate-spring-roo-entity/

The dependency:tree goal of the Maven plugin dependency supports various graphical outputs from the version 2.4 up. This is how you would create a diagram showing all dependencies in the com.example group in the dot format: mvn dependency:tree -Dincludes=com.example-DappendOutput=true -DoutputType=dot -DappendOutput=true -DoutputFile=/path/to/output.dot To actually produce an image from .dot you can use one of .dot renderers, f.ex. this online dot renderer (paste into the right text box, press enter). You could also generate the output f.ex. in the graphml format & visualize it in Eclipse. From http://theholyjava.wordpress.com/2012/01/13/visualize-maven-project-dependencies-with-dependencytree-and-dot-diagram-output/

Software Engineering is all about reuse. We programmers therefore love to split applications up into smaller components so that each of them can be reused or extended in an independent manner. A keyword here is "loose coupling". Slightly simplified, this means, each component should have as few dependencies to other components as possible. Most important, if I have a component B which relies on component A, I don't want that A needs to know about B. The component A should just provide a clean interface which could be used and extended by B. In Java there are many frameworks which provide this exact functionality: JavaEE, Spring, OSGI. However, each of those frameworks come with their own way to do things and provide lots and lots of additional functionality - whether you want it or not! Since we here at scireum love modularity (we build 4 products out of a set of about 10 independet modules) we built our own little framework. I factored out the most important parts and now have a single class with less than 250 lines of code+comments! I call this a microkernel approach, since it nicely compares to the situation we have with operating systems: There are monolithic kernels like the one of Linux with about 11,430,712 lines of code. And there is a concept called a microkernel, like to one of Minix with about 6,000 lines of executable kernel code. There is still an ongoing discussion which of the two solituons is better. A monolithic kernel is faster, a microkernel has way less critical code (critical code means: a bug there will crash the complete system. If you haven't already, you should read more about mikrokernels on Wikipedia. However one might think about operating systems - when it comes to Java I prefer less dependencies and if possible no black magic I don't understand. Especially if this magic involves complex ClassLoader structures. Therefore, here comes Nucleus... How does this work? The framework (Nucleus) solves two problems of modular applications: I want provide a service to other components - but I only want to show an interface and they should be provided with my implementation at runtime without knowning(referencing) it. I want to provide a service or callback for other components. I provide an interface, and I want to know all classes implementig it, so I can invoke them. Ok, we probably need examples for this. Say we want to implement a simple timer service. It provides an interface: public interface EveryMinute { void runTimer() throws Exception; } All classes implementing this interface should be invoked every minute. Additionally we provide some infos - namely, when was the timer executed last. public interface TimerInfo { String getLastOneMinuteExecution(); } Ok, next we need a client for our services: @Register(classes = EveryMinute.class) public class ExampleNucleus implements EveryMinute { private static Part timerInfo = Part.of(TimerInfo.class); public static void main(String[] args) throws Exception { Nucleus.init(); while (true) { Thread.sleep(10000); System.out.println("Last invocation: " + timerInfo.get().getLastOneMinuteExecution()); } } @Override public void runTimer() throws Exception { System.out.println("The time is: " + DateFormat.getTimeInstance().format(new Date())); } } The static field "Part timerInfo" is a simple helper class which fetches the registered instance from Nucleus on the first call and loads it into a private field. So accessing this part has almost no overhead to a normal field access - yet we only reference an interface, not an implementation. The main method first initializes Nucleus (this performs the classpath scan etc.) and then simply goes into an infinite loop, printing the last execution of our timer every ten seconds. Since our class wears a @Register annotation, it will be discovered by a special ClassLoadAction (not by Nucleus itself) instantiated and registered for the EveryMinute interface. Its method runTimer will then be invoced by our timer service every minute. Ok, but how would our TimerService look like? @Register(classes = { TimerInfo.class }) public class TimerService implements TimerInfo { @InjectList(EveryMinute.class) private List everyMinute; private long lastOneMinuteExecution = 0; private Timer timer; public TimerService() { start(); } public void start() { timer = new Timer(true); // Schedule the task to wait 60 seconds and then invoke // every 60 seconds. timer.schedule(new InnerTimerTask(), 1000 * 60, 1000 * 60); } private class InnerTimerTask extends TimerTask { @Override public void run() { // Iterate over all instances registered for // EveryMinute and invoke its runTimer method. for (EveryMinute task : everyMinute) { task.runTimer(); } // Update lastOneMinuteExecution lastOneMinuteExecution = System.currentTimeMillis(); } } @Override public String getLastOneMinuteExecution() { if (lastOneMinuteExecution == 0) { return "-"; } return DateFormat.getDateTimeInstance().format( new Date(lastOneMinuteExecution)); } } This class also wears a @Register annotation so that it will also be loaded by the ClassLoadAction named above (the ServiceLoadAction actually). As above it will be instantiated and put into Nucleus (as implementation of TimerInfo). Additionally it wears an @InjectList annotation on the everyMinute field. This will be processed by another class named Factory which performs simple dependency injection. Since its constructur starts a Java Timer for the InnerTimerTask, from that point on all instances registered for EveryMinute will be invoced by this timer - as the name says - every minute. How is it implemented? The good thing about Nucleus is, that it is powerful on the one hand, but very simple and small on the other hand. As you could see, there is no inner part for special or privileged services. Everything is built around the kernel - the class Nuclues. Here is what it does: It scans the classpath and looks for files called "component.properties". Those need to be in the root folder of a JAR or in the /src folder of each Eclipse project respectively. For each identified JAR / project / classpath element, it then collects all contained class files and loads them using Class.forName. For each class, it checks if it implements ClassLoadAction, if yes, it is put into a special list. Each ClassLoadAction is instanciated and each previously seen class is sent to it using: void handle(Class clazz) Finally each ClassLoadAction is notified, that nucleus is complete so that final steps (like annotation based dependency injection) could be performed. That's it. The only other thing Nucleus provides is a registry which can be used to register and retrieve objects for a class. (An in-depth description of the process above, can be found here: http://andreas.haufler.info/2012/01/iterating-over-all-classes-with.html). Now to make this framework useable as shown above, there is a set of classes around Nucleus. Most important is the class ServiceLoadAction, which will instantiate each class which wears a @Register annoation, runs Factory.inject (our mini DI tool) on it, and throws it into Nucleus for the listed classes. Whats important: The ServiceLoadActions has no specific rights or privileges, you can easily write your implementation which does smarter stuff. Next to some annotations, there are three other handy classes when it comes to retrieving instances from Nucleus: Factory, Part and Parts. As noted above, the Factory is a simple dependency injector. Currently only the ServiceLoadAction autmatically uses the Factory, as all classes wearing the @Register annotation are scanned for required injections. You can however use this factory to run injections on your own classes or other ClassLoadActions to do the same as ServiceLoadAction. If you can't or don't want to rely in annotation based dependency magic, you can use the two helper classes Part and Parts. Those are used like normal fields (see ExampleNucleus.timerInfo above) and fetch the appropriate object or list of objects automatically. Since the result is cached, repeated invocations have almost no overhead compared to a normal field. Nucleus and the example shown above is open source (MIT-License) and available here: https://github.com/andyHa/scireumOpen/blob/master/src/examples/ExampleNucleus.java https://github.com/andyHa/scireumOpen/tree/master/src/com/scireum/open/nucleus If you're interested in using Nucleus, I could put the relevant souces into a separater repository and also provide a release jar - just write a comment below an let me know. This post is the fourth part of the my series "Enterprisy Java" - We share our hints and tricks how to overcome the obstacles when trying to build several multi tenant web applications out of a set of common modules.