[CONF] Apache CXF: FAQ (page edited)

Mon, 19 Jan 2009 10:31:36 -0800

Page Edited : CXF : FAQ

FAQ has been edited by Daniel Kulp (Jan 19, 2009).

(View changes)

Content:

Frequently Asked Questions

General

Can CXF run with JDK 1.6?

JDK 1.6 incorporates the JAXB reference implementation. However, it incorporates an old version of the RI. CXF does not support this version. As of 1.6_04, this is easy to deal with: you must put the versions of JAXB RI (the 'impl' and 'xjc' jars) that we include with CXF in your classpath. As of this writing, these are version 2.1.6.

Can CXF run on JDK 1.4?

No. Many of the technologies that CXF is based on require JDK 1.5. JAX-WS, JAXB, &cetra all require JDK 1.5 feastures such as generics and annotations.

Can CXF run without the Sun reference SAAJ implementation?

Yes. CXF supports axis2-saaj version 1.4.1 as an alternative. This can make life easier if you
use a non-Sun JDK.

What's the difference between CXF and FUSE?

Progress FUSE Services Framework is based on Apache CXF to deliver a platform for developing rich service oriented applications.

Consider what Red Hat has done with Linux. Anyone can build their own Linux distribution (http://www.linuxfromscratch.org/) but few people care to do this because of the effort involved in the maintenance, support, testing, validation, etc. of such an effort. Red Hat provides the world with an easily installable Linux distribution with much value added and enterprise level services and support. FUSE is very similar to RedHat Linux insomuch as adding value to quality open source software (Apache ActiveMQ, Apache Camel, Apache Derby, Apache ServiceMix, Jetty, etc.) and providing services, support and training for a vetted version of the software.

For some additional insight into the FUSE model and how it works, see Bruce Snyder's blog entry entitled The IONA FUSE Model and It's Benefits to the Community. You can also find additional information about FUSE Services Framework and the FUSESource community at "Why join our community".

JAX-WS Related

The parts in my generated wsdl have names of the form "arg0", "arg1", ... Why don't the parts (and Java generated from them) use the nice parameter names I typed into the interface definition?

Official answer: The JAX-WS spec (specifically section 3.6.1) mandates that it be generated this way. To customize the name, you have to use an @WebParam(name = "blah") annotation to specify better names. (You can use @WebResult for the return value, but you'll only see the results if you look at the XML.)

Reason: One of the mysteries of java is that abstract methods (and thus interface methods) do NOT get their parameter names compiled into them even with debug info. Thus, when the service model is built from an interface, there is no way to determine the names that were using in the original code.

If the service is built from a concrete class (instead of an interface) AND the class was compiled with debug info, we can get the parameter names. The simple frontend does this. However, this could cause potential problems. For example, when you go from developement to production, you may turn off debug information (remove -g from javac flags) and suddenly the application may break since the generated wsdl (and thus expect soap messages) would change. Thus, the JAX-WS spec writers went the safe route and mandate that you have to use the @WebParam annotations to specify the more descriptive names.

How can I add soap headers to the request/response?

There are several ways to do this depending on how your project is written (code first or wsdl first) and requirements such a portability.

  1. The "JAX-WS" standard way to do this is to write a SOAP Handler that will add the headers to the SOAP message and register the handler on the client/server. This is completely portable from jax-ws vendor to vendor, but is also more difficult and can have performance implications. You have to handle the conversion of the JAXB objects to XML yourself. It involves having the entire soap message in a DOM which breaks streaming. Requires more memory. etc... However, it doesn't require any changes to wsdl or SEI interfaces.
  2. JAX-WS standard "java first" way: if doing java first development, you can just add an extra parameter to the method and annotate it with @WebParam(header = true). If it's a response header, make it a Holder and add the mode = Mode.OUT to @WebParam.
  3. wsdl first way: you can add elements to the message in the wsdl and then mark them as soap:headers in the soap:binding section of the wsdl. The wsdl2java tool will generate the @WebParam(header = true) annotations as above. With CXF, you can also put the headers in their own message (not the same message as the request/response) and mark them as headers in the soap:binding, but you will need to pass the -exsh true flag to wsdl2java to get the paramters generated. This is not portable to other jax-ws providers. Processing headers from other messages it optional in the jaxws spec.
  4. CXF proprietary way: In the context (BindingProvider.getRequestContext() on client, WebServiceContext on server), you can add a List<org.apache.cxf.headers.Header> with the key Header.HEADER_LIST. The headers in the list are streamed at the appropriate time to the wire according to the databinding object found in the Header object. Like option 1, this doesn't require changes to wsdl or method signatures. However, it's much faster as it doesn't break streaming and the memory overhead is less.

How can I turn on shema validation for jaxws endpoint?

For the client side

<jaxws:client name="{http://apache.org/hello_world_soap_http}SoapPort"
        createdFromAPI="true">
        <jaxws:properties>
            <entry key="schema-validation-enabled" value="true" />
        </jaxws:properties>
    </jaxws:client>

For the server side

<jaxws:endpoint name="{http://apache.org/hello_world_soap_http}SoapPort"
        wsdlLocation="wsdl/hello_world.wsdl"
        createdFromAPI="true">
        <jaxws:properties>
            <entry key="schema-validation-enabled" value="true" />
        </jaxws:properties>
    </jaxws:endpoint>


Are JAX-WS client proxies thread safe?



Official JAX-WS answer:  No.   According to the JAX-WS spec, the client proxies are NOT thread safe.   To write portable code, you should treat them as non-thread safe and synchronize access or use a pool of instances or similar.



CXF answer: CXF proxies are thread safe for MANY use cases.   The exceptions are:



    
	
  • Use of ((BindingProvider)proxy).getRequestContext() - per JAX-WS spec, the request context is PER INSTANCE.   Thus, anything set there will affect requests on other threads.   With CXF, you can do:

    

    ((BindingProvider)proxy).getRequestContext().put("thread.local.request.context", "true");
    

    

    and future calls to getRequestContext() will use a thread local request context.   That allows the request context to be threadsafe.   (Note: the response context is always thread local in CXF)
    • 





    
	
  • Settings on the conduit - if you use code or configuration to directly manipulate the conduit (like to set TLS settings or similar), those are not thread safe.   The conduit is per-instance and thus those settings would be shared.
    • 





    
	
  • Session support - if you turn on sessions support (see jaxws spec), the session cookie is stored in the conduit.  Thus, it would fall into the above rules on conduit settings and thus be shared across threads.
    • 





For the conduit issues, you COULD install a new ConduitSelector that uses a thread local or similar.   That's a bit complex though.



For most "simple" use cases, you can use CXF proxies on multiple threads.   The above outlines the workarounds for the others.   




Spring Related



When using Spring AOP to enable things like transactions and security, the generated WSDL is very messed up with wrong namespaces, part names, etc...



Reason: When using Spring AOP, spring injects a proxy to the bean into CXF instead of the actual bean.   The Proxy does not have the annotations on it (like the @WebService annotation) so we cannot query the information directly from the object like we can in the non-AOP case.   The "fix" is to also specify the actual serviceClass of the object in the spring config:




<jaxws:server 
      id="myService" 
      serviceClass="my.package.MyServiceImpl" 
      serviceBean="#myServiceImpl" 
      address="/MyService" />




or:




<jaxws:endpoint
      id="myService" 
      implementorClass="my.package.MyServiceImpl" 
      implementor="#myServiceImpl" 
      address="/MyService" />

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