Implementing private data

If the C++ class implementing your native methods requires access to C++ instance data, perform the following:

1. Add a private long type variable called “data” to your Java class:

   public class MyClass
   {
      static
      {
         com.sybase.jni.SystemUtil.loadLibrary("MyClass");
      }
   
      private long data;
   
      public native void myMethod();
   }
   

2. When you run jnicc, it now generates the C++ source and header files A_B_MyClassPrivateData.cpp and A_B_MyClassPrivateData.hpp.Add all private instance data to the A_B_MyClassPrivateData class. You can add any methods you want to this class.

3. Add a public finalize method that calls a private destroy method. The JNI compiler ensures that when the destroy method is called, the C++ instance data is deleted.

   public class MyClass
   {
      static
      {
         com.sybase.jni.SystemUtil.loadLibrary("MyClass");
      }
   
      private long data;
   
      public native void myMethod();
   
      public void finalize()
      {
         destroy();
      }
   
      private native void destroy();
   }
   

4. Access the instance data from your native methods using the data variable—see the sample in samples/SimpleRowSet.