Name: md23716 Date: 10/25/99


If getPreferredSize is called after setLayout(null), within a
Frame's getNotify method, a NullPointerException is thrown.

i.e. overriding addNotify in a Frame;

public void addNotify()
    {
        super.addNotify();

        setLayout(null); //Remove this and problem does not occur

        setBackground(bColor);

        int i = getPreferredSize().height; //The exception is thrown here
    }

Throws..........

java.lang.NullPointerException: null peer
        at sun.awt.windows.WFramePeer.getMinimumSize(WFramePeer.java:28)
        at sun.awt.windows.WComponentPeer.getPreferredSize(WComponentPeer.java:123)
        at sun.awt.windows.WComponentPeer.preferredSize(WComponentPeer.java:369)
        at java.awt.Component.preferredSize(Component.java:1017)
        at java.awt.Container.preferredSize(Container.java:559)
        at java.awt.Container.getPreferredSize(Container.java:541)
        at MainFrame.addNotify(MainFrame.java:37)
        at java.awt.Window.show(Window.java:141)
        at java.awt.Component.show(Component.java:506)
        at java.awt.Component.setVisible(Component.java:468)
        at MainFrame.setVisible(MainFrame.java:25)
        at MainFrame.<init>(MainFrame.java:18)
        at MainFrame.main(MainFrame.java:10)

Does NOT occur on Sun reference port 118.

The problem occurs in the new native methods 'getSysMin(Max)Width'
in awt_Window.cpp which get called with a null WWindowPeer
reference. The methods explicitly check this and throw the observed
'null peer' exception.
These methods were ported into our code from a Sun fix relating to
a previous defect (SunBug 422955).
The g118n reference port does NOT include this fix. The g117n
reference port DOES include this fix and throws the exception as
per n117p and n118p.

A note from the customer;

Tom,
thanks for your hint on the setLayout method. I scanned through our
code, but could not find any occurrence of setLayout(null) for the
failing component. Actually no setLayout at all is done for this
component which is of type JToolBar in our case.
.
Unfortunately I'm not able to create a small testcase for you, as
the problem occurs only about at every 10th application startup, and
even then it does not occur in my development environment but on a
system test machine in the IBM Poughkeepsie lab. To me it looks very
much like a timing issue.
.
But we will try follow up on the hint you gave with the setLayout()
method and see if there is something we can do to solve our problem.

In case you might want to have a look at our code or even tryout the
product itself you can go to our webpage and download the latest
version (45). It is available as installable as well as a zipfile
containing all of our sourcecode. The relevant part is SMAppl.java,
located in bbon/html/classes/com/ibm/cb390sm. In case you don't want
to download the whole source, here is just that one part:

(/defects/11684/SMAppl.java)

The method where to exception occurs is doShowToolbar().

The webpage is: CB390 Systems Management EUI
(http://boedom1.boeblingen.de.ibm.com/domino/webnsf/s_390sw/
        ha3151/ha3151.nsf/lookup/CB390+Systems+Management+EUI)
-----------------------------
Note by Phil Vickers, JTC, IBM

This bug is caused by the declaration of the native
methods 'getSysMinWidth' and 'getSysMinHeight' in
WWindowPeer.java.

They are declared as static native int and the JNI
does not therefore pass 'this' as the self
Hsun_awt_windows_WWindowPeer* parameter
across the JNI.

This could be cured in two ways :-

(1) Remove check on 'self' in the awt_Window.cpp
native methods. As all they do is call Win32 APIs
and return a primitive type this should be OK.

However, I think the more elegant solution is to
change the Java native method declaration to
'public native int' whence all is well.

After discussing this with Matthew White, who did the
Sun port, we decided that the designers original
intent was probably to make the new methods static and
that there is a simple mistake made in copying a function
template inside awt_Window.cpp

I'll remove the check on 'self' in this code and add a
comment to warn that the method is static.




(Review ID: 96965)

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