[CONF] Apache CXF 2.0 Documentation: Interceptors (page edited)

Tue, 13 Nov 2007 20:39:33 -0800

Page Edited : CXF20DOC : Interceptors

Interceptors has been edited by Glen Mazza (Nov 13, 2007).

Change summary:

Clarification made for interceptor system (thanks Willem and Jervis!)

(View changes)

Content:

Interceptors and Phases

Interceptors are the fundamental processing unit inside CXF. When a service is invoked, an InterceptorChain is created and invoked. Each interceptor gets a chance to do what they want with the message. This can include reading it, transforming it, processing headers, validating the message, etc.

Interceptors are relevant for both CXF clients and CXF servers. When a CXF client invokes a CXF server, there is an outgoing interceptor chain for the client and an incoming chain for the server. When the server sends the SOAP response back to the client, there is an outgoing chain for the server and an incoming one for the client.

Some examples of interceptors inside CXF include:

  • SoapActionInterceptor - Processes the SOAPAction header and selects an operation if its set.
  • StaxInInterceptor - Creates a Stax XMLStreamReader from the transport input stream.
  • Attachment(In/Out)Interceptor - Turns a multipart/related message into a series of attachments.

InterceptorChains are divided up into Phases. Each phase contains many interceptors. On the incoming chains, you'll have the following phases:

Phase Functions
RECEIVE Transport level processing
(PRE/USER/POST)_STREAM Stream level processing/transformations
READ This is where header reading typically occurs.
(PRE/USER/POST)_PROTOCOL Protocol processing, such as JAX-WS SOAP handlers
UNMARSHAL Unmarshalling of the request
(PRE/USER/POST)_LOGICAL Processing of the umarshalled request
PRE_INVOKE Pre invocation actions
INVOKE Invocation of the service
POST_INVOKE Invocation of the outgoing chain if there is one

On the outgoing chain there are the following phases:

Phase Functions
SETUP Any set up for the following phases
(PRE/USER/POST)_LOGICAL Processing of objects about to marshalled
PREPARE_SEND Opening of the connection
PRE_STREAM  
PRE_PROTOCOL Misc protocol actions.
WRITE Writing of the protocol message, such as the SOAP Envelope.
MARSHAL Marshalling of the objects
(USER/POST)_PROTOCOL Processing of the protocol message.
(USER/POST)_STREAM Processing of the byte level message
SEND Final sending of message and closing of transport stream

InterceptorProviders

Several different components inside CXF may provide interceptors to an InterceptorChain. These implement the InterceptorProvider interface:

public interface InterceptorProvider {
    
    List<Interceptor> getInInterceptors();
    
    List<Interceptor> getOutInterceptors();
    
    List<Interceptor> getOutFaultInterceptors();
    
    List<Interceptor> getInFaultInterceptors();
}


To get an interceptor added to the interceptor chain, you'll want to add it to one of the Interceptor Providers.




MyInterceptor interceptor = new MyInterceptor();
provider.getInInterceptors().add(interceptor);





There are main InterceptorProviders inside CXF are:


    
	
  • Client
    • 
	
  • Endpoint
    • 
	
  • Service
    • 
	
  • Bus
    • 
	
  • Binding
    • 





Writing an Interceptor


Writing an interceptor is relatively simple. The best way to do this is to extend from an abstract class. 



Practically speaking, there are two base classes you will be concerned with. The first is the AbstractPhaseInterceptor. The second is AbstractSoapInterceptor. The only difference between the two is that the latter will give you a SoapMessage instead of just a Message class. This allows you to access the SOAP headers and version.



Here is a small example of how to write a Soap interceptor:




public class MySoapInterceptor extends AbstractSoapInterceptor {
  public MySoapInterceptor () {
    super(Phase.PRE_PROTOCOL);
  }

  public MySoapInterceptor (String phase) {
    super(phase);
  }

  public void handleMessage(SoapMessage msg) throws SoapFault {
    System.out.println("Hello World!");
  }
}





To add this to your server, you'll want to get access to the Server object (see here for more info):




MySoapInterceptor myInterceptor = new MySoapInterceptor();

Server server = serverFactoryBean.create();
server.getEndpoint().getInInterceptor().add(myInterceptor);





On the Client side the process is very similar:




FooService client = ... ; // created from ClientProxyFactoryBean or generated JAX-WS client
MySoapInterceptor myInterceptor = new MySoapInterceptor();

Client cxfClient = ClientProxy.getClient(client);
cxfClient .getInInterceptor().add(myInterceptor);





You may also want to specify what phase your interceptor is in. To do this, you can simply set the phase:




public class MySoapInterceptor extends AbstractSoapInterceptor {
  public MySoapInterceptor() {
    super(Phase.USER_PROTOCOL);
  }
  ...
}





You can also express that you would like your interceptor to run before/after certain other interceptors in the same phase:




public class MySoapInterceptor extends AbstractSoapInterceptor {
  public MySoapInterceptor() {
    super(Phase.USER_PROTOCOL);
    getAfter().add(SomeOtherInterceptor.class.getName());
  }
  ...
}

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