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https://issues.apache.org/jira/browse/CXF-8590?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17408202#comment-17408202
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Freeman Yue Fang commented on CXF-8590:
---------------------------------------
Hi [~kim.johan.andersson],
Thanks for raising this question!
Just FYI, per the document here
http://cxf.apache.org/faq.html#FAQ-AreJAX-WSclientproxiesthreadsafe?
JAX-WS client proxies are not thread safe, you should use synchronize access or
use a pool of instances for the multiple client proxies you used in your
code(which means you can't use a bunch of client proxies at the same time,
instead you should synchronize access the client proxies).
CXF Client proxies are not thread safe for several cases, not only the conduit
configuration(which is your case since the policy got involved here), but also
a few other cases as mentioned in CXF
[FAQ|http://cxf.apache.org/faq.html#FAQ-AreJAX-WSclientproxiesthreadsafe?].
Freeman
> First invocation of method causes NPE failure in neethi.PolicyBuilder
> ---------------------------------------------------------------------
>
> Key: CXF-8590
> URL: https://issues.apache.org/jira/browse/CXF-8590
> Project: CXF
> Issue Type: Bug
> Components: Core, WS-* Components
> Affects Versions: 3.4.4
> Reporter: Kim Johan Andersson
> Priority: Major
>
> I have a multithreaded application where each thread does the following:
> new SomeService
> .getPort()
> .invokeSomeEndpointMethod()
>
> The first invocation of the endpoint method cases the following error:
> {noformat}
> java.lang.reflect.InvocationTargetException
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:498)
> at
> org.apache.neethi.builders.converters.ConverterRegistry.findQName(ConverterRegistry.java:121)
> at
> org.apache.neethi.PolicyBuilder.processOperationElement(PolicyBuilder.java:204)
> at
> org.apache.neethi.PolicyBuilder.getPolicyOperator(PolicyBuilder.java:174)
> at org.apache.neethi.PolicyBuilder.getPolicy(PolicyBuilder.java:124)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:192)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:168)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy(Wsdl11AttachmentPolicyProvider.java:161)
> at
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getEffectivePolicy(Wsdl11AttachmentPolicyProvider.java:75)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getAggregatedServicePolicy(PolicyEngineImpl.java:461)
> at
> org.apache.cxf.ws.policy.EndpointPolicyImpl.initializePolicy(EndpointPolicyImpl.java:151)
> at
> org.apache.cxf.ws.policy.EndpointPolicyImpl.initialize(EndpointPolicyImpl.java:140)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.createEndpointPolicyInfo(PolicyEngineImpl.java:614)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getEndpointPolicy(PolicyEngineImpl.java:326)
> at
> org.apache.cxf.ws.policy.PolicyEngineImpl.getClientEndpointPolicy(PolicyEngineImpl.java:313)
> at
> org.apache.cxf.ws.policy.PolicyDataEngineImpl.getClientEndpointPolicy(PolicyDataEngineImpl.java:61)
> at
> org.apache.cxf.transport.http.HTTPConduit.updateClientPolicy(HTTPConduit.java:326)
> at
> org.apache.cxf.transport.http.HTTPConduit.updateClientPolicy(HTTPConduit.java:346)
> at
> org.apache.cxf.transport.http.HTTPConduit.getClient(HTTPConduit.java:892)
> at
> org.apache.cxf.transport.http.HTTPConduit.configureConduitFromEndpointInfo(HTTPConduit.java:368)
> at
> org.apache.cxf.transport.http.HTTPConduit.finalizeConfig(HTTPConduit.java:448)
> at
> org.apache.cxf.transport.http.HTTPTransportFactory.getConduit(HTTPTransportFactory.java:249)
> at
> org.apache.cxf.binding.soap.SoapTransportFactory.getConduit(SoapTransportFactory.java:226)
> at
> org.apache.cxf.binding.soap.SoapTransportFactory.getConduit(SoapTransportFactory.java:233)
> at
> org.apache.cxf.endpoint.AbstractConduitSelector.createConduit(AbstractConduitSelector.java:144)
> at
> org.apache.cxf.endpoint.AbstractConduitSelector.getSelectedConduit(AbstractConduitSelector.java:108)
> at
> org.apache.cxf.endpoint.UpfrontConduitSelector.prepare(UpfrontConduitSelector.java:63)
> at
> org.apache.cxf.endpoint.ClientImpl.prepareConduitSelector(ClientImpl.java:887)
> at org.apache.cxf.endpoint.ClientImpl.doInvoke(ClientImpl.java:525)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:441)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:356)
> at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:314)
> at org.apache.cxf.frontend.ClientProxy.invokeSync(ClientProxy.java:96)
> at
> org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:140)
> ...
> at
> org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)
> Caused by: java.lang.NullPointerException
> at
> com.sun.org.apache.xerces.internal.dom.DeferredElementNSImpl.synchronizeData(DeferredElementNSImpl.java:108)
> at
> com.sun.org.apache.xerces.internal.dom.ElementNSImpl.getLocalName(ElementNSImpl.java:338)
> at
> org.apache.neethi.builders.converters.AbstractDOMConverter.getQName(AbstractDOMConverter.java:43)
> ... 45 more
> {noformat}
>
> From there on, everything works fine. The service in question uses policies,
> and apparently policies are lazily initialized.
> The actual failure is triggered by a race condition causing ElementNSImpl
> from xerces to be being shared across threads as a consequence.
> This happens in
> org.apache.cxf.ws.policy.attachment.wsdl11.Wsdl11AttachmentPolicyProvider.getElementPolicy,
> when the PolicyRegistry is consulted:
> {noformat}
> Policy policy = registry.lookup(id);
> if (policy == null) {
> try {
> policy = builder.getPolicy(e.getElement());
> {noformat}
>
> All threads will start building the missing policy, as there is nothing in
> the registry and no synchronization on a cache miss. Some thread wins the
> race and gets a usable result from e.getElement() and stores the result in
> the registry, the others hit the NPE-error.
> I do not really understand all the internal workings, but I can cure this
> problem by changing the code snippet to:
> {noformat}
> synchronized (e.getElement()) {
> Policy policy = registry.lookup(id);
> if (policy == null) {
> try {
> policy = builder.getPolicy(e.getElement());
>
> ...
> }
> {noformat}
> That solves the race to initialize the entry in the registry, but not the
> real problem.
> This leaves me with 3 questions:
> Is there a way to eagerly populate the PolicyRegistry as an user of CXF?
> Shouldn't Wsdl11AttachmentPolicyProvider be thread safe, if policies are to
> be lazily initialized?
> How do we prevent the WSDLManager in the Service from sharing non-tread safe
> items (ElementNSImpl) across threads?
> Apparently org.apache.cxf.jaxws.ServiceImpl.initialize always selects the
> same bus, which cases the WSDLManager to be shared between threads. Normally
> that would be a good thing, since we can share the WSDL-cache.
> I tried to build a test-case, so far I have no luck in building the required
> configuration. Also, which submodule is to blame here? A lot of components
> are involved.
> Please ask for more details if required.
> Thanks,
> Kim Johan Andersson
>
>
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