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https://issues.apache.org/jira/browse/TUSCANY-2085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587156#action_12587156
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Ramkumar Ramalingam commented on TUSCANY-2085:
----------------------------------------------
To prevent ConcurrentModificationException, one way is to lock the entire List
while you are iterating by wrapping it with a synchronized block, which inturn
looks costly as the this would block the other thread to access the list for
reading.
A better solution i would consider for the above problem would be, using
CopyOnWriteArrayList class from util.concurrent (which will also appear in the
java.util.concurrent package in JDK 1.5) is a thread-safe implementation of
ArrayList that offers far better concurrency. Multiple reads can almost always
execute concurrently, simultaneous reads and writes can usually execute
concurrently, and multiple simultaneous writes can often execute concurrently.
Also CopyOnWriteArrayList contains a mutable reference to an immutable array,
so as long as that reference is held fixed, you get all the thread-safety
benefits of immutability without the need for locking.
The code change required would be just to replace the ArrayList with
CopyOnWriteArrayList:
private final List<DataBinding> databindings = new
CopyOnWriteArrayList<DataBinding>();
> ConcurentModExc in DefaultDataBindingExtensionPoint
> ----------------------------------------------------
>
> Key: TUSCANY-2085
> URL: https://issues.apache.org/jira/browse/TUSCANY-2085
> Project: Tuscany
> Issue Type: Bug
> Components: Java SCA Data Binding Runtime
> Affects Versions: Java-SCA-1.1
> Reporter: Scott Kurz
> Priority: Minor
> Fix For: Java-SCA-Next
>
> Attachments: 2085.patch
>
>
> Get an exception like the following,
> java.util.ConcurrentModificationException
> at java.util.AbstractList$SimpleListIterator.next(Unknown Source)at
> org.apache.tuscany.sca.databinding.DefaultDataBindingExtensionPoint.introspectType(DefaultDataBindingExtensionPoint.java:223)
> at
> org.apache.tuscany.sca.interfacedef.java.jaxws.JAXWSFaultExceptionMapper.introspectFaultDataType(JAXWSFaultExceptionMapper.java:214)
> at
> org.apache.tuscany.sca.interfacedef.java.jaxws.JAXWSJavaInterfaceProcessor.introspectFaultTypes(JAXWSJavaInterfaceProcessor.java:178)
> at
> org.apache.tuscany.sca.interfacedef.java.jaxws.JAXWSJavaInterfaceProcessor.visitInterface(JAXWSJavaInterfaceProcessor.java:90)
> at
> org.apache.tuscany.sca.interfacedef.java.impl.JavaInterfaceIntrospectorImpl.introspectInterface(JavaInterfaceIntrospectorImpl.java:91)
> as this thread, A, is in a for-loop looping through 'databindings'
> public boolean introspectType(DataType dataType, Annotation[] annotations,
> boolean isException) {
> loadDataBindings();
> for (DataBinding binding : databindings) {
> while another thread, B, is still in loadDataBindings() and is still adding
> to the databindings ArrayList.
> I'm working around this by putting a lock around the whole body of
> loadDataBindings()
> private final byte[] loadingLock = new byte[0];
> ...
> private void loadDataBindings() {
> synchronized (loadingLock) {
> if (loadedDataBindings)
> return;
> ...
> }
> }
> Another option might be to change addDataBinding() to look at the 'bindings'
> Map before adding to 'databindings'.
> I'll attach a patch and leave it for a second opinion.
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