javaswingnetbeansnullpointerexceptionmatisse

Not executing certain code when loading form in mattise


I have a JPanel that I designed in NetBeans' Mattise form editor. I now want to include this form in a JFrame. However, this is failing because in the contructor of the JPanel, it refers to a static variable from elsewhere in the program, which in the form editor is null, because it is only initialized in the program elsewhere, before the JFrame is loaded, so it comes up with a NullPointerException.

public UserManagementPanel() {
    initComponents();
    loadUserRequest();
}

private void loadUserRequest() {
    GetUserListRequest req = new GetUserListRequest();
    req.setListener(this);
    transcription.Main.cq.addRequest(req);
}

It fails on the call to transcription.Main.cq.addRequest, because it is not initialized.

java.lang.NullPointerException
at transcription.users.UserManagementPanel.loadUserRequest(UserManagementPanel.java:28)
at transcription.users.UserManagementPanel.<init>(UserManagementPanel.java:22)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
at java.lang.Class.newInstance(Class.java:433)
at org.netbeans.modules.form.CreationFactory.createDefaultInstance(CreationFactory.java:178)
at org.netbeans.modules.form.RADComponent.createBeanInstance(RADComponent.java:252)
at org.netbeans.modules.form.RADComponent.initInstance(RADComponent.java:191)
at org.netbeans.modules.form.GandalfPersistenceManager.restoreComponent(GandalfPersistenceManager.java:780)
at org.netbeans.modules.form.GandalfPersistenceManager.loadComponent(GandalfPersistenceManager.java:968)
at org.netbeans.modules.form.GandalfPersistenceManager.restoreComponent(GandalfPersistenceManager.java:824)
at org.netbeans.modules.form.GandalfPersistenceManager.loadComponent(GandalfPersistenceManager.java:968)
at org.netbeans.modules.form.GandalfPersistenceManager.loadForm(GandalfPersistenceManager.java:503)
at org.netbeans.modules.form.GandalfPersistenceManager.loadForm(GandalfPersistenceManager.java:283)
at org.netbeans.modules.form.FormEditor$2.run(FormEditor.java:352)
at org.netbeans.modules.form.FormLAF$2.run(FormLAF.java:293)
at org.openide.util.Mutex.doEventAccess(Mutex.java:1376)
at org.openide.util.Mutex.readAccess(Mutex.java:327)
at org.netbeans.modules.form.FormLAF.executeWithLookAndFeel(FormLAF.java:276)
at org.netbeans.modules.form.FormEditor.loadFormData(FormEditor.java:349)
at org.netbeans.modules.nbform.FormEditorSupport.loadOpeningForm(FormEditorSupport.java:467)
at org.netbeans.modules.nbform.FormDesignerTC.loadForm(FormDesignerTC.java:279)
at org.netbeans.modules.nbform.FormDesignerTC.access$300(FormDesignerTC.java:87)
at org.netbeans.modules.nbform.FormDesignerTC$PreLoadTask$1.run(FormDesignerTC.java:268)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:744)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:714)
at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:159)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

This piece of code is not important for the form editor - I only need that code to be run in the actual program. Is there a way I can tell the form editor to ignore that code when initializing it?


Solution

  • In the end, I did a simple workaround - I caught and ignored the NullPointerException:

    private void loadUserRequest() {
        GetUserListRequest req = new GetUserListRequest();
        req.setListener(this);
        try {
            transcription.Main.cq.addRequest(req);
        } catch (NullPointerException e) {}
    }
    

    This isn't a perfect solution, because if for some reason during actual program execution cq would actually be null, then I would want it to throw an exception, so I'm curious if anyone else has a more elegant solution.