Exception when retreiveing list from JNDI when the list updates at the same time.

Question

Hi
I get a Exception when i am retreiving a list from the jndi:
Start server side stack trace:
com.sun.java.util.collections.ConcurrentModificationException
at java.lang.Throwable.fillInStackTrace(Native Method)
at java.lang.Throwable.fillInStackTrace(Compiled Code)
at java.lang.Throwable.<init>(Compiled Code)
at java.lang.Exception.<init>(Compiled Code)
at java.lang.RuntimeException.<init>(Compiled Code)
at
com.sun.java.util.collections.ConcurrentModificationException.<init>(Concurr
entModificationException.java:48)
at com.sun.java.util.collections.HashMap$HashIterator.next(Compiled
Code)
at
weblogic.jndi.toolkit.ReadOnlyMapBasedNamingStore$1.nextElement(Compiled
Code)
at weblogic.jndi.toolkit.AbstractNamingEnumeration.next(Compiled
Code)
at
weblogic.jndi.toolkit.AbstractNamingEnumeration.nextElement(Compiled Code)
at
weblogic.utils.enumerations.BatchingEnumerationBase.nextBatch(Compiled Code)
at
weblogic.utils.enumerations.BatchingEnumerationBase_WLSkel.invoke(BatchingEn
umerationBase_WLSkel.java:66)
at weblogic.rmi.extensions.BasicServerObjectAdapter.invoke(Compiled
Code)
at
weblogic.rmi.extensions.BasicRequestHandler.handleRequest(Compiled Code)
at
weblogic.rmi.internal.BasicExecuteRequest.execute(BasicExecuteRequest.java:1
5)
at weblogic.kernel.ExecuteThread.run(Compiled Code)
End server side stack trace
It says in the documentation of the weblogic server that: if the jndi is
updated while you are retreiving the list from the server, you will only get
the old list.
And that is ok for me. But insted i get this exception that interupts the
list retreiving. And if i just catch this exception an just continue or
start again, it comes over and over.
the code that does this, is like this:
InitialContext context = new InitialContext(env);
NamingEnumeration list = context.listBindings("sid");
Vector copy = new Vector(10000,1000);
log("Initiating copy of JNDI list!");
try
while (list.hasMore())
copy.addElement(list.next());
catch (Exception e)
log("Copying interupted:" + e.toString());
How can i solve this ?
Is it a configuration of the server problem ?
Are ther other ways of retreiving the list ?
-Ståle Tomten

Answer 1

Be carefull - you read Object two times, so if you
have only one object you will get null after second
reading, and NullPointerException as a result if you
try to do smth with null.
Wrong:
while( inputFromServlet1.readObject() != null)
Object o = inputFromServlet1.readObject();Previous man example is also wrong because you
cannot declare anything in while
Sorry for this one... I certainly must have spent too much time on these fora ;-)
Thanks for the correction, by the way...
Correct:
Object o;
while( (o = inputFromServlet1.readObject()) != null)
String str = (String)o;
System.out.println("Got Object");