Extreme Java

When registering files on NBM’s layer file, you can define attributes, too:

<file name="my-pkg-MyClass.instance">
  <attr name="mystr" stringvalue="value"/>
  <attr name="myint" intvalue="1"/>
  <attr name="mymethod"
    methodvalue="my.pkg.MyClass.myMethod"/>
</file>

They are avaliable as attributes of FileObject (through getAttribute). You can also use special attributes “instanceClass” to define a different class to instantiate or “instanceCreate” to define a factory method. This factory method can receive a map of attributes. I’m using it to customize a generic DataLoader:

public class MyLoader extends MultiDataLoader {
  private MyDataLoader(String secondaryExt) {
    super("MyObject");
    this.secondaryExt = secondaryExt;
  }
  public static build(Map<String, Object> attrs) {
    return new MyLoader(attrs.get("ext").toString());
  }
  ...
}

If you want to use NetBeans Platform and JPA together, there’s a great tutorial on NB’s site. Unfortunatelly, it explains how to do it with an external database and using an external JAR for your entities.

If you want to have a entity module with your classes (instead of an external JAR and a library wrapper), no big deal - it works! You can follow GJ’s tutorial, but you will create a module project instead and you will not have NB’s wizards to help creating entity classes.

I also created a module install on my Derby wrapper, with this line:

FileUtil configRoot = FileUtil.getConfigRoot();
System.setProperty("derby.system.home",
    FileUtil.toFile(configRoot).getCanonicalPath());

This defines where Derby will create database files (user’s dir, in this case).

BTW, if a “no suitable driver found” is thrown, you forgot to add a dependency between JPA wrapper (EclipseLink, TopLink, OpenJPA or Hibernate) and JDBC wrapper.