ConcurrentModificationException during registration of nodetypes
----------------------------------------------------------------
Key: JCR-713
URL: https://issues.apache.org/jira/browse/JCR-713
Project: Jackrabbit
Issue Type: Bug
Components: core
Affects Versions: 1.1.1
Reporter: Martijn Hendriks
During the registration of a set of nodetypes this exception may be encountered:
java.util.ConcurrentModificationException
at
org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.checkMod(AbstractReferenceMap.java:761)
at
org.apache.commons.collections.map.AbstractReferenceMap$ReferenceEntrySetIterator.hasNext(AbstractReferenceMap.java:735)
at
org.apache.jackrabbit.core.nodetype.NodeTypeRegistry.notifyRegistered(NodeTypeRegistry.java:1750)
at
org.apache.jackrabbit.core.nodetype.NodeTypeRegistry.registerNodeTypes(NodeTypeRegistry.java:223)
It seems that the copying of the listeners triggered this exception:
private void notifyRegistered(QName ntName) {
// copy listeners to array to avoid ConcurrentModificationException
NodeTypeRegistryListener[] la =
new NodeTypeRegistryListener[listeners.size()];
Iterator iter = listeners.values().iterator();
int cnt = 0;
1750: while (iter.hasNext()) {
la[cnt++] = (NodeTypeRegistryListener) iter.next();
}
for (int i = 0; i < la.length; i++) {
if (la[i] != null) {
la[i].nodeTypeRegistered(ntName);
}
}
}
The methods "notifyReRegistered" and "notifyUnregistered" will probably suffer
from the same problem.
Reproduction of this exception may be tricky; it only occurred once in our
application. It is probably a race condition: another thread might access the
listeners during the copy. It may be helpful to use a debugger and set a
breakpoint in the middle of the copy giving other threads the opportunity to
access the listeners...
We think that a possible solution is the following:
/**
* Notify the listeners that a node type <code>ntName</code> has been
registered.
*/
private void notifyRegistered(QName ntName) {
// copy listeners to array to avoid ConcurrentModificationException
NodeTypeRegistryListener[] la;
synchronized (listeners) {
la = (NodeTypeRegistryListener[]) listeners.values().toArray(new
NodeTypeRegistryListener[listeners.size()]);
}
for (int i = 0; i < la.length; i++) {
if (la[i] != null) {
la[i].nodeTypeRegistered(ntName);
}
}
}
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