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How to Create a Swing CRUD Application on NetBeans Platform 6.8

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Wrapping the Entity Class JAR in a Module

In this section, you add your first module to your application! The new NetBeans module will wrap the JAR file you created in the previous section.

  1. Right-click the DBManager's Modules node in the Projects window and choose Add New Library.

  2. Select the JAR you created in the previous subsection and complete the wizard, specifying any values you like. Let's assume the application is for dealing with customers at, in which case a unique identifier "" is appropriate for the code name base:

    unique id for module

You now have your first custom module in your new application, wrapping the JAR containing the entity classes and the persistence.xml file:


Creating Other Related Modules

In this section, you create two new modules, wrapping the EclipseLink JARs, as well as the database connector JAR.

  1. Do the same as you did when creating the library wrapper for the entity class JAR, but this time for the EclipseLink JARs, which are in the "CustomerLibrary" Java library that you created earlier:

    wrapping a library

    Note: In the Library Wrapper Module wizard, you can use Ctrl-Click to select multiple JARs.

  2. Next, create yet another library wrapper module, this time for the Java DB client JAR, which is available in your JDK distribution, at db/lib/derbyclient.jar.

Designing the User Interface

In this section, you create a simple prototype user interface, providing a window that uses a JTextArea to display data retrieved from the database.

  1. Right-click the DBManager's Modules node in the Projects window and choose Add New. Create a new module named CustomerViewer, with the code name base

  2. In the Projects window, right-click the new module and choose New | Window Component. Specify that it should be created in the editor position and that it should open when the application starts. Set Customer as the window's class name prefix.

  3. Use the Palette (Ctrl-Shift-8) to drag and drop a JTextArea on the new window:

    JTextArea dropped

  4. Add this to the end of the TopComponent constructor:
    EntityManager entityManager = Persistence.createEntityManagerFactory("CustomerLibraryPU").createEntityManager();
    Query query = entityManager.createQuery("SELECT c FROM Customer c");
    List<Customer> resultList = query.getResultList();
    for (Customer c : resultList) {
    jTextArea1.append(c.getName() + " (" + c.getCity() + ")" + "\n");

    Note: Since you have not set dependencies on the modules that provide the Customer object and the persistence JARs, the statements above will be marked with red error underlines. These will be fixed in the section that follows.

  5. Above, you can see references to a persistence unit named "CustomerLibraryPU", which is the name set in the persistence.xml file. In addition,there is a reference to one of the entity classes, called Customer, which is in the entity classes module. Adapt these bits to your needs, if they are different to the above.

Setting Dependencies

In this section, you enable some of the modules to use code from some of the other modules. You do this very explicitly by setting intentional contracts between related modules, i.e., as opposed to the accidental and chaotic reuse of code that tends to happen when you do not have a strict modular architecture such as that provided by the NetBeans Platform.

  1. The entity classes module needs to have dependencies on the Derby Client module as well as on the EclipseLink module. Right-click the CustomerLibrary module, choose Properties, and use the Libraries tab to set dependencies on the two modules that the CustomerLibrary module needs.

  2. The CustomerViewer module needs a dependency on the EclipseLink module as well as on the entity classes module. Right-click the CustomerViewer module, choose Properties, and use the Libraries tab to set dependencies on the two modules that the CustomerViewer module needs.

  3. Open the CustomerTopComponent in the Source view, right-click in the editor, and choose "Fix Imports". The IDE is now able to add the required import statements, because the modules that provide the required classes are now available to the CustomerTopComponent.

You now have set contracts between the modules in your application, giving you control over the dependencies between distinct pieces of code.

Running the Prototype

In this section, you run the application so that you can see that you're correctly accessing your database.

  1. Start your database server.

  2. Run the application. You should see this:

    running the prototype

You now have a simple prototype, consisting of a NetBeans Platform application that displays data from your database, which you will extend in the next section.

Published at DZone with permission of its author, Geertjan Wielenga.


Craig Ringer replied on Wed, 2009/12/09 - 12:17am

This example doesn't appear to take the need to avoid blocking the UI while performing database work into account. While that keeps it simple, it also makes it a fairly useless example of using the platform in practice, as such concurrency issues are crucual when doing database work.

Geertjan Wielenga replied on Wed, 2009/12/09 - 12:27am

Excellent feedback, ringerc. That will be fixed. Thank you. One approach is to register actions in the layer file which then enables you to add an attribute to the layer entry. That attribute causes the action to be processed asynchronously, (which is a new feature in 6.8, i.e., the ability to mark an action as being asynchronous). These asynchronous actions can simulate SwingWorker:

class MyAction implements ActionListener, Runnable {
public MyAction(MyContext c) {
assert EventQueue.isEventThread();
// setup inside AWT thread, get what is important from c
public void actionPerformed(AE ev) {
assert !EventQueue.isEventThread();
// run off AWT thread
// perform the work

public void run() {
assert EventQueue.isEventThread();
// finish in AWT and update the UI


Another approach would be to use SwingWorker. These approaches will be added to the article, though note that threading on the NetBeans Platform is also discussed here:

Something else that's possible is to integrate with the NetBeans progress bar, which can be achieved with, literally, 3 lines of code.

Suraj Chhetry replied on Wed, 2009/12/09 - 4:04am

Thanks for great toturail. Could you tell me how can I create flollowing type of menu at TopComponent how can i do this ?



       - Greetjan        







Florian Brunner replied on Thu, 2009/12/10 - 5:42am

Hi Geertjan,

great to have another tutorial about this topic. Thanks!

Though I haven't read all of it yet, I already have one enhancement question:

As you know, the NetBeans IDE provides a project template to create the skeleton of a CRUD application based on the Swing Application Framework.

Maybe it would be useful to have a project template  to create the skeleton of a CRUD application based on the NetBeans Platform, too. What do you think?



Geertjan Wielenga replied on Sun, 2009/12/13 - 6:51am

Hi Florian, that would be wonderful and is something I've been thinking of working on... sometime... when I have the time to do so... At least now there is a tutorial (the one to which these are the comments) describing how to do it and, yes, the next step would be to have a wizard that generates the code and you'd use the tutorial to understand what's been generated.

Dans Cut replied on Mon, 2009/12/14 - 10:40am

for geertjan....please reply my message please....I need your help...thanks u...

Geertjan Wielenga replied on Mon, 2009/12/14 - 12:06pm in response to: Dans Cut

I already replied. You want a CRUD tutorial, well, this IS a CRUD tutorial.

Geertjan Wielenga replied on Mon, 2009/12/14 - 6:56pm

Hi surajchchetry, that's a great idea. If I understand it correctly. This is the kind of project structure I am creating at the moment, for a new tutorial, based on your suggestion above.

A new tutorial should appear within the next week or two, to explain how to create project structures like the above, with a bunch of additional features too, as described here in my blog!


Nguyen Khiem replied on Mon, 2009/12/21 - 7:23am

hi, does it require jdk 6 for this ? i tried it on a mac ppc ( jdk5) and run into some problems while starting the app, mth like eclipselink cannot acces some libraries in javax.resources,** and unknown entity Customer. thanx

Kevin Jaques replied on Sun, 2010/01/03 - 12:25pm

In the part where you instruct us to create the CustomerChildFactory class, you should specify where (CustomerViewer, in

Kevin Jaques replied on Sun, 2010/01/03 - 12:47pm

In the Read Section, step 6, it says to put in several lines of codes somewhere in the TopComponent, but it didn't say where. In fact, all but one of those lines already existed. In fact, since it appears to be a replacement for the 'for' loop that we previously commented out, it would be far more clear to have left the 'for' loop in place till this step, then simply say, "In the constructor of the TopComponent, replace the 'for' loop with the following line:

em.setRootContext(new AbstractNode(Children.create(new CustomerChildFactory(resultList), true)));"

That also drives home part of the reason for the change.

Kevin Jaques replied on Sun, 2010/01/03 - 1:02pm

In the Read Section, step 7, you instruct us to run the Application. It won't compile till the imports are fixed. Ditto step 9.

Farouk Alhassan replied on Tue, 2010/01/19 - 3:08pm

Hi Geertjan

Thank you very much for such a great tutorial. Following the tutorials from here and the JPA intergration in the Definitive guide to Netbeans Platform I am trying to develop a real database application from the concepts explained. I am however not getting a any success.

In this tutorial, the EntityManager is created in the constructor of the TopComponent class which is not very efficient for obvious reasons and will also be a night mare to maintain if every TopComponent creates its own Entitymanager. I therefore tried the Installer approach used in the Netbeans Platform book but that didn't work. I kept getting ClasscastException when retreiving the objects via creating the nodes for the Viewer with ExplorerManager.

  protected boolean createKeys(List<Pupilidentifiers> list) {
      for (Pupilidentifiers identifier : resultList) {
    return true;

Que 1. What is the recommended way of using these API's and JPA in a production environment?

To get my application off the ground,

I have now moved the Node creation code to the componentOpened() method and calling the entity manager creation directly but that is throwing the following errors with regards

associateLookup(ExplorerUtils.createLookup(exm, map));

java.lang.IllegalStateException: Trying to set lookup ProxyLookup(class=class org.openide.explorer.DefaultEMLookup)->[org.openide.explorer.DefaultEMLookup$NoNodeLookup@5b695ffa, org.openide.util.Lookup$Empty@375212bc, org.openide.util.lookup.SingletonLookup@631c44f8] but there already is java.lang.ref.WeakReference@54f4289d for component: PupilViewer.PupilTopComponent[Pupil Window,0,0,0x0,invalid,layout=javax.swing.GroupLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=256,maximumSize=,minimumSize=,preferredSize=]

Que 2. Is it not possible to call that method in the componentOpened() method?

Vladimír Duša replied on Tue, 2010/02/09 - 3:29pm

Hi Geertjan,

thanks for this super tutorial - it helped me a lot.

I still have a problem with saving the customer. The save button works as I expect, but the save action is not invoked during closing the TopComponent and switching between customers. After few hours of googling I have no Idea how to do it using SaveCookie and SaveCookieImpl model. Is there a possibility, to manually invoke the same save action as the save button? It would be good to invoke this save action in componentClosed() and resultChanged() methods.

Thank you very much

Vladimír Duša

John Hetherington replied on Wed, 2010/05/26 - 8:16pm

Started working through this article on Netbeans 6.8, completed the read section successfuly and got the tree displaying with the properties synchronised. Commenced on the update section and got down to Step 4 which states Go back to the Customer Viewer module and change the layer.xml file and specify that the CustomerTopComponent window will appear in the explorer mode.

 Has anyone the neccessary xml code to add here to make this happen as none is included in the article??

 Kind Regards

John In New Zealand

Ralph Lance replied on Tue, 2010/06/29 - 4:38am in response to: John Hetherington

Change the name attribute from "editor" to "explorer" under "Modes".

Hadi Setyono replied on Thu, 2010/07/01 - 5:32am

I want to make an application for user management with net beans. i read this article and i think that it can solve my requirement. can you show me the step how to make this application with netbeans with spring framework ?

Andreas Niepsch replied on Tue, 2010/07/20 - 6:02am

Hi Geertjan,


thank's for this tutorial. It's a very good start for developing  Rcp and Database-Applikations.

I have two questions:

1. If i close  "Customer Window" the content of "Editor Window" isn't clear, wy??? or what should i do?

I think if a TComponent is closed  the Lookup of is is not longer in the Global Context and not displayed in

the "Editor Windows" ????


2. The save-button is enabled if i mouseClicked in  "Editor Window". Enabling if changed content of the

form  is better in this sample.



Thank you





Craig Ringer replied on Tue, 2010/07/27 - 2:41am

There are issues with driving Swing directly with JPA entities when you start doing anything non-trivial, involving larger amounts of data. You start to need to lazily load parts of entities or entity relationships, and have to worry about how much data you're retaining in memory at once. This gives rise to issues with EDT blocking again, and major problems with managing JPA session lifetimes.

If you're going to be working with enough data that you don't want to download it from the database server all at once, think very carefully about whether this is the approach for you.

Anyone considering writing a non-trivial app driven directly by JPA data access should read this excellent article:

 ... and possibly my own inferior writing on the topic, which covers some issues not considered by the above link:

 The only solutions I've found to the issues involve writing a (probably complex and boilerplate-heavy) mid-tier to buffer between Swing and JPA.

Craig Ringer replied on Tue, 2010/07/27 - 2:57am in response to: Farouk Alhassan

@gcameo: I'm not the smartest developer around, nor the strongest JPA expert, but my personal advice after recent experience trying to use JPA in a Swing app is: run, run, as fast as you can.

You'll have to write a midlayer to mediate between Swing and your JPA data access to get acceptable performance, avoid blocking the UI, etc. Even then it'll be "interesting" to manage JPA session lifetimes. I'm currently seriously considering ripping JPA out of my app entirely and going back to JDBC, because I'm finding it creates more problems than it solves in a 2-tier Swing app.

I'd be glad to be proved wrong, of course. Just so long as that "wrong" doesn't involve some comment about how you should "obviously" write a 3-teir appserver based monstrosity that communicates with the Swing rich client via RMI. I don't have an army of bored coders who need make-work, I need to get a real application written ;-)

I have direct personal messages enabled, and my email address is:

python -c "print 'Y3JhaWdAcG9zdG5ld3NwYXBlcnMuY29tLmF1\n'.decode('base-64')"

I don't seem to get email comment reply notifications, though.

Tj Harple replied on Tue, 2011/02/15 - 5:05pm

Hi Geertjan

Thank you very much for such a great tutorial. This is only my 2nd tutorial with Java 1.6.0_23 & NetBeans 6.9.1 on Windows 7. I was following the tutorial here :

and had a strange issue for which only by chance I found the work around here on dzone.

My issue:

cannot find symbol
symbol  : method actionsGlobalContext()
location: class javax.swing.text.Utilities
      result = Utilities.actionsGlobalContext().lookupResult(Customer.class);

Which was worked around by the change:

 result = WindowManager.getDefault().findTopComponent("CustomerTopComponent").getLookup().lookupResult(Customer.class);

But my question...

Clearly it looks like I was missing a library dependencey. But when looking all over the internet, no one else had this issue, or spoke about using actionsGlobalContext with a specific dependency.

Is this a resent change that you may be aware of, or does it sound like my configuration may be suspect.

Can you suggest or point me to a resource which would allow me to figure out these types of dependencies on my own. In other words which file located in which directory contains this method.

 Also, I have noted a few minor changes needed in the tutroial based on my configuration and would be willing to update or provide suggestion if that was appropriate. Is that work done here on dzone or via

Thanks in Advance

Terry Harple




Mark Green replied on Sat, 2011/07/30 - 8:18pm

In Step 6.  How does the company name get to the node?  How do you specify which field to use?  Try another table and see!

Johnson Eyo replied on Wed, 2011/08/24 - 5:48am

i need some update on why netbans module should be used instead of a basic java desktop application,i noticed the new module project after been build might require you to install.pls anyone help,need to be clear

Johnson Eyo replied on Tue, 2011/09/13 - 3:50am

my program still refuses to build the customerlibrary to a jar file,i get these errors onh the console window,


Updating property file: C:\CustomerLibrary\build\
Deleting directory C:\CustomerLibrary\build
Created dir: C:\CustomerLibrary\build
Updating property file: C:\CustomerLibrary\build\
Created dir: C:\CustomerLibrary\build\classes
Created dir: C:\CustomerLibrary\build\classes\META-INF
Copying 1 file to C:\CustomerLibrary\build\classes\META-INF
Created dir: C:\CustomerLibrary\build\empty
Created dir: C:\CustomerLibrary\build\generated-sources\ap-source-output
Compiling 2 source files to C:\CustomerLibrary\build\classes
Note: Creating non-static metadata factory ...

An annotation processor threw an uncaught exception.
Consult the following stack trace for details.
java.lang.NoSuchMethodError: javax.annotation.processing.RoundEnvironment.getRootElements()Ljava/util/Set;
    at org.eclipse.persistence.internal.jpa.modelgen.MetadataMirrorFactory.setEnvironments(
    at org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor.process(
C:\CustomerLibrary\nbproject\build-impl.xml:603: The following error occurred while executing this line:
C:\CustomerLibrary\nbproject\build-impl.xml:245: Compile failed; see the compiler error output for details.
BUILD FAILED (total time: 7 seconds)


please help with these, because of this i can continue the rest of the tutorial

Carla Brian replied on Sun, 2012/05/06 - 7:32am

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