Axis2 generated Stubs are thread-safe?

Question

Are the Stubs generated by WSDL2JAVA (using XMLBeans binding option) through Axis2 1.5.4 thread-safe?

Actually I have created one Stub for a Web Service that I am invoking through multiple threads. I have configured my own MultiThreadedHttpConnectionmanager and set the HTTPConstants.REUSE_HTTP_CLIENT as well but I am seeing some NullPointerExceptions in stub._getServiceClient().cleanupTransport that I call after each invocation.

Sometimes the threads hang too.

At the same time I noticed that in the generated Stub in the Web Service operation method, cleanup() is called already in the finally block. Should I not call stub._getServiceClient().cleanupTransport myself afterwards?

My code:

        httpConnMgr = new MultiThreadedHttpConnectionManager();
        HttpConnectionManagerParams params = httpConnMgr.getParams();
        if (params == null) {
            params = new HttpConnectionManagerParams();

        }
        params.setDefaultMaxConnectionsPerHost(numberOfThreads);
        httpConnMgr.setParams(params);
        HttpClient httpClient = new HttpClient(httpConnMgr);

        service = new Service1Stub(this.endPointAddress);
        service._getServiceClient().getOptions()
                .setTimeOutInMilliSeconds(this.timeOut);
        service._getServiceClient().getOptions()
                .setProperty(HTTPConstants.REUSE_HTTP_CLIENT, Boolean.TRUE);
        service._getServiceClient().getOptions()
        .setProperty(HTTPConstants.AUTO_RELEASE_CONNECTION, Boolean.FALSE);
        service._getServiceClient()
                .getOptions()
                .setProperty(HTTPConstants.SO_TIMEOUT, (int) (this.timeOut));
        service._getServiceClient()
                .getOptions()
                .setProperty(HTTPConstants.CONNECTION_TIMEOUT,
                        (int) (this.timeOut));
        service._getServiceClient().getServiceContext().getConfigurationContext()
                .setProperty(HTTPConstants.CACHED_HTTP_CLIENT, httpClient);

Meanwhile in the generated stub, I noticed that cleanUp is already been called:

   finally {
            _messageContext.getTransportOut().getSender().cleanup(_messageContext);
        }

Any suggestion would be greatly helpful. Thanks.

Answer 1

When I looked into Axis2 some time ago, I also had thread-safe related questions about it.

Finding information about Axis2's thread safety was difficult, but I finally ended up with the following Jira issue: https://issues.apache.org/jira/browse/AXIS2-4357

It is mentioned that:

Axis2 client side is not thread safe, and which was the case from the beginning of the project [...] use different stubs for different threads [...]

The issue itself is closed with a Won't Fix status and with the following note:

Axis2 stubs are not thread safe. As Deepal pointed out this is by design.

That about did it for me at that time.

Basically you need to use one stub per thread or you can use a stub pool as (if I remember correctly) the stubs can be reused (but still need to use one stub per thread to avoid any issues). Other seem to have used stub pools with success (see related SO question here).

One advice I usually follow regarding thread safety is: If it is not explicitly stated that something is thread safe, then assume it is not.