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https://issues.apache.org/jira/browse/XMLRPC-167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12707327#action_12707327
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Alan Burlison commented on XMLRPC-167:
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Well it could be made thread safe very easily, at least in the case of the Sun
transport. And if not, at very least the documentation needs changing, as
saying that XmlRpcClient is thread-safe rather misleading, as it depends on the
transport factory and transport it is configured to use.
In my case I assume the correct thing to do is to modify my transport factory
so that it returns a new instance of the transport on each call to
getTransport, rather than using a singleton as it does at present, is that
correct?
With the exception of the addition of 'synchronized' to
XmlRpcSunHttpTransport.sendRequest(), I think the rest of the patch can stand
as it cleans up a few other issues, what do you think?
> XmlRpcClient is supposed to be thread-safe but it isn't
> -------------------------------------------------------
>
> Key: XMLRPC-167
> URL: https://issues.apache.org/jira/browse/XMLRPC-167
> Project: XML-RPC
> Issue Type: Bug
> Components: Source
> Affects Versions: 3.1.2
> Environment: Solaris
> Reporter: Alan Burlison
> Attachments: XMLRPC-167.patch
>
>
> http://ws.apache.org/xmlrpc/apidocs/org/apache/xmlrpc/client/XmlRpcClient.html
> says:
> ----------
> A configured XmlRpcClient object is thread safe: In other words, the
> suggested use is, that you configure the client using
> setTransportFactory(XmlRpcTransportFactory) and similar methods, store it in
> a field and never modify it again. Without modifications, the client may be
> used for an arbitrary number of concurrent requests.
> ----------
> I have a simple test case that creates two threads that share a single
> XmlRpcClient instance, and if I run the test I see the following errors:
> ----------
> Fatal Error] :1:1: Content is not allowed in prolog.
> operation failed, Failed to parse server's response: Content is not allowed
> in prolog.
> [Fatal Error] :1:10: Element type "xlvrsion" must be followed by either
> attribute specifications, ">" or "/>".
> operation failed, Failed to parse server's response: Element type "xlvrsion"
> must be followed by either attribute specifications, ">" or "/>".
> ----------
> ----------
> [Fatal Error] :1:1: Content is not allowed in prolog.
> [Fatal Error] :1:5: Element type "xlv" must be followed by either attribute
> specifications, ">" or "/>".
> operation failed, Failed to parse server's response: Element type "xlv" must
> be followed by either attribute specifications, ">" or "/>".
> operation failed, Failed to parse server's response: Content is not allowed
> in prolog.
> ----------
> If I wrap the call to XmlRpcClient.execute with a synchronized block that
> locks on the XmlRpcClient object, the code works fine.
> It looks like the execute code is not locking around the read/write to/from
> the server, so the threads are competing to read the response from the
> server, and are tripping over each other.
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