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From "Kevin Sutter (JIRA)" <j...@apache.org>
Subject [jira] Created: (OPENJPA-304) Problems with DepthFirstAnalysis and the IBM JDK
Date Tue, 31 Jul 2007 15:34:52 GMT
Problems with DepthFirstAnalysis and the IBM JDK
------------------------------------------------

                 Key: OPENJPA-304
                 URL: https://issues.apache.org/jira/browse/OPENJPA-304
             Project: OpenJPA
          Issue Type: Bug
          Components: lib
    Affects Versions: 0.9.7
            Reporter: Kevin Sutter
            Assignee: Kevin Sutter
             Fix For: 1.0.0


TestDepthFirstAnalysis was reporting two errors when running with the IBM JDK.  The testcase
ran just fine with the Sun JDK.  The error conditions were NPE's in testBackEdges and testForwardEdges:

testBackEdges(org.apache.openjpa.lib.graph.TestDepthFirstAnalysis)  Time elapsed: 0 sec  <<<
ERROR!
java.lang.NullPointerException
        at org.apache.openjpa.lib.graph.DepthFirstAnalysis.visit(DepthFirstAnalysis.java:97)
        at org.apache.openjpa.lib.graph.DepthFirstAnalysis.<init>(DepthFirstAnalysis.java:74)
        at org.apache.openjpa.lib.graph.TestDepthFirstAnalysis.setUpGraph2 (TestDepthFirstAnalysis.java:78)
        at org.apache.openjpa.lib.graph.TestDepthFirstAnalysis.testBackEdges(TestDepthFirstAnalysis.java:105)
        :

testForwardEdges(org.apache.openjpa.lib.graph.TestDepthFirstAnalysis)  Time elapsed: 0 sec
 <<< ERROR!
java.lang.NullPointerException
        at org.apache.openjpa.lib.graph.DepthFirstAnalysis.visit(DepthFirstAnalysis.java:97)
        at org.apache.openjpa.lib.graph.DepthFirstAnalysis.<init>(DepthFirstAnalysis.java
:74)
        at org.apache.openjpa.lib.graph.TestDepthFirstAnalysis.setUpGraph2(TestDepthFirstAnalysis.java:78)
        at org.apache.openjpa.lib.graph.TestDepthFirstAnalysis.testForwardEdges(TestDepthFirstAnalysis.java
:129)
        :

Some debugging with the IBM JDK turned up a couple of problems:

1)  The code in DepthFirstAnalysis.java and Edges.java was using == for equality testing instead
of .equals().  It turns out that the IBM JDK has an optimization when using Integer instances
as keys to HashMaps and new copies of the keys are created (vs using the input key objects
directly).  Thus, the == check was not sufficient to do the comparison testing.

2)  After performing those updates, there was yet another problem with the order of the entries
returned by the iterator() of the HashMap.  By definition, the
order is not guaranteed with a HashMap implementation.  In these particular failing testcases,
the Sun JDK was starting with node 2 via the Iterator, while the IBM JDK was starting with
node 5.  By changing the declaration of this Graph._nodes structure to use a LinkedHashMap
(instead of HashMap), we can
reliably determine the order of the iterator.  And, now both the Sun and IBM JDK's produce
the same results.

Thanks,
Kevin

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