Name: gsC80088 Date: 03/05/99


We are trying to use the Plugin as a bridge to expose our Java beans as ActiveX
controls for use in COM environments (typically VB). However, we have a serious
problem withthe VM monotonically growing in size. We have traced this to the fact
that seemingly *ALL* Java objects passed back to the VB environment are *NEVER*
reclaimed. It looks like the Plugin is still holding references to the Java
objects preventing them from being garbage collected. The process eventually
runs out of memory and VB signals Automation Errors.

Included are 2 tests that demonstrate the leak and verify that the Java objects
passed back to VB are never reclaimed. This can be reproduced in both the 1.1.2
and 1.2 Plugins.

Cut and paste the included text into the files named in the separators.
Run all commands from the directory in which the files are saved out.

To show the leak:
Compile MyBean.java
Run packagemybean.bat
Run VB and put MyBean on the palette. Create a single instance to cover the form
and write the following callback
Private Sub MyBean1_mouseMoved(ByVal MouseEvent1 As Object)
    Dim x As String
    x = MyBean1.toString
End Sub
Bring up the task manager and sort by Mem Usage.
Run the form and examine memory of the VB process. As long the callback isn't
being called, memory usage is flat. Moving the mouse over the form invoked the
callback fetching a String from Java. Memory usage grows unboundedly.

To verify that the the Java objects passed to VB are never reclaimed:
Compile MyBean2.java
Run packagemybean2.bat
Run VB and put MyBean2 on the palette. Create a single instance on the form and
write the following callback
Private Sub MyBean21_mouseClicked(ByVal MouseEvent1 As Object)
    Dim x As Object
    Set x = MyBean21.getFoo
End Sub
Run the form and watch the memory stats (# of beans /# of large objects) in
the dialog displayed. Hit the "Run GC" button to establish a baseline. Click
on the control in the form. Note that 2 LargeObjects are created and one is
passed back to VB as the return value of the getFoo call. Hit the GC button
again. Note that one of the LargeObjects is reclaimed (GC looks like it's
kicking in correctly) but not the other. Repeat the experiment by clicking
on the control and running the GC. One of the two newly allocated objects
is never reclaimed.

I could not find any reported bugs. We are desparate for
a fix or workaround and would appreciate a response as soon as possible. Thank you.

Regards,
Vikram Pillai
Project Leader, Telewindows2
Gensym Corporation
Cambridge MA 02140
(617) 588 9207
###@###.###

-XX----Save to MyBean.java-----------------------------------------------------
public class MyBean extends java.awt.Component {


public MyBean () {
}

}
-XX---Save to mybean.mf-------------------------------------------------------
Name: MyBean.class
Java-Bean: true

-XX---Save to packagemybean.bat-----------------------------------------------
jar cfm MyBean.jar mybean.mf MyBean.class
java -classpath "%CLASSPATH%;C:\jdk1.2\jre\lib\jaws.jar" sun.beans.ole.Packager -n MyBean -jar MyBean.jar -o C:\temp




-XX---Save to MyBean2.java----------------------------------------------------
import java.awt.*;
import java.awt.event.*;
import java.util.Date;

public class MyBean2 extends Component {

  private static MsgDialog monitor;
  private static GCDialog gcControlPanel;
  private static String msg = "\nHello\n";
  static final String CR = "\n";
  private static int beanCount;
  private LargeObject foo;

  static {
    try {
      monitor = new MsgDialog ();
      gcControlPanel = new GCDialog ();
      new GCThread ().start ();
      monitor.setVisible (true);
      gcControlPanel.setVisible (true);
    } catch (Exception e) {
      System.err.println (e);
    }
  }

  static void setMessage (String newMsg) {
    monitor.setMessage ("# Beans = " + beanCount + " / # LargeObjects = " + LargeObject.objCount + "\n" + newMsg);
  }

  public MyBean2 () {
    beanCount += 1;
  }

  public void paint (Graphics g) {
    g.setColor (Color.red);
    Dimension size = getSize ();
    g.fillRect (0, 0, size.width, size.height);
  }

  public void finalize () {
    beanCount -= 1;
  }

  public LargeObject getFoo () {
    new LargeObject ();
    return new LargeObject ();
  }

  public void dumpFoo () {
  }
}

class GCThread extends Thread {

  private static final String CR = MyBean2.CR;
  public synchronized void run () {
    MyBean2.setMessage ("Starting Thread");
    Runtime rt = Runtime.getRuntime ();
    while (true) {
      try {
sleep (1000);
long currentTime = System.currentTimeMillis ();
String timeStamp = new Date(currentTime).toString();
long freeMemory = rt.freeMemory ();
long totalMemory = rt.totalMemory ();
StringBuffer sb = new StringBuffer (320);
sb.append (timeStamp).append(CR).append("Total Memory = " + totalMemory).
append(CR).append("Free Memory = " + freeMemory);
MyBean2.setMessage (sb.toString ());
      } catch (Exception e) {
System.err.println (e);
      }
    }
  }

}
class GCDialog extends Dialog {

  GCDialog () {
    super (new Frame(), "GC Panel", false);
    Button gcButton;
    add (gcButton = new Button ("Run GC"));
    gcButton.addActionListener (new ActionListener () {
      public void actionPerformed (ActionEvent aEvt) {
Runtime rt = Runtime.getRuntime ();
rt.runFinalizersOnExit (true);
System.out.println ("FM0 = " + rt.freeMemory ());
rt.gc ();
rt.runFinalization ();
System.out.println ("FM1 = " + rt.freeMemory ());
rt.gc ();
rt.runFinalization ();
System.out.println ("FM2 = " + rt.freeMemory ());
      }
    });
    pack ();
  }

}

class MsgDialog extends Dialog {

  private TextArea ta;

  MsgDialog () {
    super (new Frame (), "Bean Monitor", false);
    add (ta = new TextArea (), BorderLayout.CENTER);
    pack ();
  }

  void setMessage (String newMsg) {
    ta.setText (newMsg);
  }

}

class LargeObject {

  private int[] array = new int[10000];
  static int objCount = 0;

  LargeObject () {
    objCount++;
  }

  public void finalize () {
    objCount--;
  }

}
-XX---Save to mybean2.mf----------------------------------------------------------
Name: MyBean2.class
Java-Bean: true

-XX---Save to packagemybean2.bat--------------------------------------------------
jar cfm MyBean2.jar mybean2.mf *.class
java -classpath "%CLASSPATH%;C:\jdk1.2\jre\lib\jaws.jar" sun.beans.ole.Packager -n MyBean2 -jar MyBean2.jar -o C:\temp
(Review ID: 55107)
======================================================================

Name: yyT116575 Date: 01/09/2001


java version "1.2.2"
Classic VM (build JDK-1.2.2-001, native threads, symcjit)


Overview Of the application:
   we are designing a java application which talks to the COM component using
Java to Com Bridge (Jacob)provided by microsoft. we hava java client & java
server. Java client talks to the java server using RMI. java Implementation
Object which is bound into the RMI registry creates the object of ActiveXComponent
Class. Using this object i am doing JNI calls to communicate with my COM object.
as long as i am calling some methods on that object it is alive. once i stop calling the
methods the object is garbage collected and doesn't wait for callbacks comming
from my COM component. we have tried the following things to avoid it.

OUR TRILAL:1

In our first trial we did insert a thread in the Implementation class and pass the
ActiveXObject to the thread. With some Swaping and function calling we did try
to make the ActiveXObject persistant. But we were not successfull, and the
object still got Garbage Collected.

DEMO CODE:

//frist I Declare the ActiveX Object at Class Level in my Implementation Class
ActiveXObject axb1;
//I do Construct ActiveXObject in my Implementation Constructor.
ActiveXObject axb1 = new ActiveXObject();
//then,
public void run()
{
  while(true)
  {
    ActiveXObject axb2;
    abx2 = abx1;
    abx1 = abx2;
    //calling some method of COM component using ActiveXObject
    Dispatch.call(abx1,"SomeMethod",Some Parameter);

    //Sleep thread for some time
  }
}


/*OUR TRILAL:2

After some R&D we came to know that the Distributed Garbage Collector is
Specifically Collecting it into garbage, but a normal Garbage Collector In
Java does not Collect the ActiveX Object.The Only Condition is (naturally)
the Class should be running infinitly. But now even if ActiveX Object is not
geting Garbage Collocted it is not responding at all. The object is there in
the memory but it is useless. Here lies the trouble. How an existing object,
which is there in the memory cannot be used? Only thing is that if we make
calls to the method immediately as soon as the AxtiveXObject is Created
the Calls do get Executed. But As soon as the Calling is Stopped, the
object immedialely become useless and stops responding.

Demo Code :

1.)// Interface (MyInterface.java)
    //one methods signature
    Variant callTrailCall(Object ServerNode,Object Node,long Rate) throws RemoteException;

2.)// MyImpl.java in which i implement MyInterface
    public Variant callTrailCall(Object ServerNode,Object Node,long Rate) throws RemoteException
    {
      return tc.trailCallMeth(ServerNode, Node, Rate);//method belong to TrailCall class, discribed below
    }

4.)// In TrailCall.java I have:

public void getActiveObj(ActiveXComponent temp1, Object xlo) {
  temp = temp1;
  xlo1 = xlo;
}
public Variant trailCallMeth(Object ServerNode, Object Node, long Rate) {
  //calling some method of COM component using ActiveX Object
  return Dispatch.call(xlo1,"InvokeServer",parameter1,parameter2,parameter3);
  //At this point i get A com Fail exception.
}

5.)TrailCallRun.java in which I construct the AxtiveX Object and call the
getActiveObj(ActiveXComponent temp1, Object xlo) method of TrailCall class and
pass the AxtiveX Object As a parameter to TrailCall Class also there is a method
in which there is a infinite while loop to keep the class running infinitly

//required Declerations
public TrailCallRun(TrailCall tc) {
  System.out.println("In TrailCallRun Constructor 2");
  this.tc = tc;
  ActiveXComponent temp1 = new ActiveXComponent("ClientOPC.Document");
  Object xlo = temp1.getObject();
  String s = "xlo";
  tc.getActiveObj(temp1, xlo);
  myStart();
}
void myStart() {
  while(true)
  {
  //Sleep for some time
  }
}

6.)// Server program (MyServer.java) in which I register my MyImpl object.

//in my main meth.
TrailCall tc = new TrailCall();
myImpl obj = new myImpl(tc);
Naming.rebind("MyInterface",obj);
TrailCallRun tcr = new TrailCallRun(tc);
(Review ID: 114790)
======================================================================