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 used with 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 response back to the client, there is an outgoing chain for the server and an incoming one for the client. Additionally, the service will create a separate error handling interceptor chain in the case of SOAPFaults.

Some examples of interceptors inside CXF include:

SoapActionInterceptor - Processes the SOAPAction header and selects an operation if it's 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 may contain 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 add an interceptor to an interceptor chain, you'll want to add it to one of the Interceptor Providers.

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

Some InterceptorProviders inside CXF are:

Client
Endpoint
Service
Bus
Binding

Writing and configuring an Interceptor

The CXF distribution is shipped with a demo called configuration_interceptor which shows how to develop a user interceptor and configure the interceptor into its interceptor chain.

Writing an Interceptor

Writing an interceptor is relatively simple. Your interceptor needs to extend from either the AbstractPhaseInterceptor or one of its many subclasses such as AbstractSoapInterceptor. Extending from AbstractPhaseInterceptor allows your interceptor to access the methods of the Message interface. For example, AttachmentInInterceptor is used in CXF to turn a multipart/related message into a series of attachments. It looks like below:

import java.io.IOException;

import org.apache.cxf.attachment.AttachmentDeserializer;
import org.apache.cxf.message.Message;
import org.apache.cxf.phase.AbstractPhaseInterceptor;
import org.apache.cxf.phase.Phase;

public class AttachmentInInterceptor extends AbstractPhaseInterceptor<Message> {
    public AttachmentInInterceptor() {
        super(Phase.RECEIVE);
    }

    public void handleMessage(Message message) {
        String contentType = (String) message.get(Message.CONTENT_TYPE);
        if (contentType != null && contentType.toLowerCase().indexOf("multipart/related") != -1) {
            AttachmentDeserializer ad = new AttachmentDeserializer(message);
            try {
                ad.initializeAttachments();
            } catch (IOException e) {
                throw new Fault(e);
            }
        }
    }

    public void handleFault(Message messageParam) {
    }
}

Extending from sub-classes of AbstractPhaseInterceptor allows your interceptor to access more specific information than those in the Message interface. One of the sub-classes of AbstractPhaseInterceptor is AbstractSoapInterceptor. Extending from this class allows your interceptor to access the SOAP?header and version information of the SoapMessage class. For example, SoapActionInInterceptor is used in CXF to parse the SOAP action, as a simplified version of it shows below:

import java.util.Collection;
import java.util.List;
import java.util.Map;

import org.apache.cxf.binding.soap.Soap11;
import org.apache.cxf.binding.soap.Soap12;
import org.apache.cxf.binding.soap.SoapMessage;
import org.apache.cxf.binding.soap.model.SoapOperationInfo;
import org.apache.cxf.endpoint.Endpoint;
import org.apache.cxf.helpers.CastUtils;
import org.apache.cxf.interceptor.Fault;
import org.apache.cxf.message.Exchange;
import org.apache.cxf.message.Message;
import org.apache.cxf.phase.Phase;
import org.apache.cxf.service.model.BindingOperationInfo;
import org.apache.cxf.service.model.OperationInfo;

public class SoapActionInInterceptor extends AbstractSoapInterceptor {

    public SoapActionInInterceptor() {
        super(Phase.READ);
        addAfter(ReadHeadersInterceptor.class.getName());
        addAfter(EndpointSelectionInterceptor.class.getName());
    }

    public void handleMessage(SoapMessage message) throws Fault {
        if (message.getVersion() instanceof Soap11) {
            Map<String, List<String>> headers = CastUtils.cast((Map)message.get(Message.PROTOCOL_HEADERS));
            if (headers != null) {
                List<String> sa = headers.get("SOAPAction");
                if (sa != null && sa.size() > 0) {
                    String action = sa.get(0);
                    if (action.startsWith("\"")) {
                        action = action.substring(1, action.length() - 1);
                    }
                    getAndSetOperation(message, action);
                }
            }
        } else if (message.getVersion() instanceof Soap12) {
          ...........
        }
    }

    private void getAndSetOperation(SoapMessage message, String action) {
        if ("".equals(action)) {
            return;
        }

        Exchange ex = message.getExchange();
        Endpoint ep = ex.get(Endpoint.class);

        BindingOperationInfo bindingOp = null;

        Collection<BindingOperationInfo> bops = ep.getBinding().getBindingInfo().getOperations();
        for (BindingOperationInfo boi : bops) {
            SoapOperationInfo soi = (SoapOperationInfo) boi.getExtensor(SoapOperationInfo.class);
            if (soi != null && soi.getAction().equals(action)) {
                if (bindingOp != null) {
                    //more than one op with the same action, will need to parse normally
                    return;
                }
                bindingOp = boi;
            }
        }
        if (bindingOp != null) {
            ex.put(BindingOperationInfo.class, bindingOp);
            ex.put(OperationInfo.class, bindingOp.getOperationInfo());
        }
    }

}

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

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

You can add your interceptors into the interceptor chain either programmatically or through configuration.

Adding interceptors programmatically

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

import org.apache.cxf.endpoint.Server;
import org.apache.cxf.frontend.ServerFactoryBean;
...

MyInterceptor myInterceptor = new MyInterceptor();

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

On the Client side the process is very similar:

import org.apache.cxf.endpoint.Client;
import org.apache.cxf.frontend.ClientProxy;
...

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

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

Adding interceptors through configuration

The configuration file page provides examples on using configuration files to add interceptors.

Adding MyInterceptor to the bus:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:cxf="http://cxf.apache.org/core"
       xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://cxf.apache.org/core http://cxf.apache.org/schemas/core.xsd">

    <bean id="MyInterceptor" class="demo.interceptor.MyInterceptor"/>

    <!-- We are adding the interceptors to the bus as we will have only one endpoint/service/bus. -->

    <cxf:bus>
        <cxf:inInterceptors>
            <list>
                <ref bean="MyInterceptor"/>
            </list>
        </cxf:inInterceptors>
        <cxf:outInterceptors>
            <list>
                <ref bean="MyInterceptor"/>
            </list>
        </cxf:outInterceptors>
    </cxf:bus>
</beans>

For embedded Jetty-based web services, the configuration file can be declared by starting the service with the -Dcxf.config.file=server.xml option. See the server configuration section on the configuration file page for information on specifying the file for servlet WAR file-based web service implementations.

Adding MyInterceptor to your client:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:http="http://cxf.apache.org/transports/http/configuration"
       xsi:schemaLocation="http://cxf.apache.org/transports/http/configuration http://cxf.apache.org/schemas/configuration/http-conf.xsd
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <http:conduit name="{http://apache.org/hello_world_soap_http}SoapPort9001.http-conduit">
      <http:client DecoupledEndpoint="http://localhost:9990/decoupled_endpoint"/>
    </http:conduit>

    <bean id="MyInterceptor" class="demo.interceptor.MyInterceptor"/>

    <!-- We are adding the interceptors to the bus as we will have only one endpoint/service/bus. -->

    <bean id="cxf" class="org.apache.cxf.bus.CXFBusImpl">
        <property name="inInterceptors">
            <list>
                <ref bean="MyInterceptor"/>
            </list>
        </property>
        <property name="outInterceptors">
            <list>
                <ref bean="MyInterceptor"/>
            </list>
        </property>
    </bean>
</beans>

To specify the client-side configuration file, start your client using the -Dcxf.config.file=client.xml option.

Child pages

Interceptors