[jira] [Created] (CXF-8041) Error resolving relative XSD Schema on Tomcat

["Mike M. (JIRA)" <ji...@apache.org>]

Mike M. created CXF-8041:
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             Summary: Error resolving relative XSD Schema on Tomcat
                 Key: CXF-8041
                 URL: https://issues.apache.org/jira/browse/CXF-8041
             Project: CXF
          Issue Type: Bug
          Components: Core, Transports
    Affects Versions: 3.3.1
            Reporter: Mike M.
         Attachments: cxf-tomcat-resource-resolver.zip

We found an issue in a CXF JAX-WS project when running in WSDL-first mode with schema-validation enabled on Tomcat. The WSDL references an external XSD schema using a relative path. The WSDL and XSD are bundled with the application and are present on the classpath.

Expectation:
The XSD should be resolved successfully and schema validation should work.

Actual behavior:
* The resource lookup runs through CXF {{EndpointReferenceUtils}}' {{SchemaLSResourceResolver}}. This one runs through multiple strategies for resolving the imported XSD URL to a resource. One of them (currently around line 150) is an attempt to ask a {{ResourceManager}} for the URL.
* In a Servlet context, this will be handled by CXF's {{ServletContextResourceResolver}}. This one (currently starting around line 82) will ask the actual {{ServletContext}} for the URL. While doing so, it will catch and ignore {{MalformedURLException}}s as documented in the {{ServletContext}} interface as well as {{URISyntaxException}}s (probably precautionary).
* Entering Tomcat's implementation: the call will go through Tomcat's {{ApplicationContext}} and end up in the {{StandardRoot}}'s {{#validate(String)}} method. Unfortunately, while validating the provided URL, this one throws {{IllegalArgumentException}}s instead of just returning {{null}}. In our case, since we resolve the XSD schema relative to the WSDL and need to go up some levels (../../) from it, Tomcat thinks we're trying to escape the application context and will trigger the {{IllegalArgumentException}}.
* Unfortunately though, this exception never gets caught and propagates up the stack back to CXF's {{SchemaLSResourceResolver#resolveResource}}. This method had several strategies for resolving resources, remember? The annoying part is: we didn't even need that particular ServletContext strategy for our XSD, and one of the other methods (classpath lookup) would have resolved the XSD just fine, *had the ServletContext lookup not thrown the {{IllegalArgumentException}}*. That uncaught exception however, breaks the lookup entirely.

Solution proposal:
I think the least invasive solution would be for {{ServletContextResourceResolver}} to additionally catch {{IllegalArgumentException}} when calling {{ServletContext#getResource}}. It already catches {{URISyntaxException}} even though that one isn't documented by the {{ServletContext}} API. Catching an exception that basically says "Hey, this argument isn't valid" would be semantically similar imho.
A more drastic approach would be catching all {{RuntimeException}}s from the Servlet Container in order to fulfill {{ResourceResolver#resolve}}'s contract, namely: "@return an instance of the resource or null if the resource cannot be resolved".

Reproducing the error:
I attached a sample project to this ticket that reproduces the issue. Make sure to follow the instructions in its README.md.



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