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Specifying an interceptor's phase

Overview

Interceptors are organized into phases. An interceptor's phase determines when in the message processing sequence it is called. Developers specify an interceptor's phase its constructor. Phases are specified using constant values provided by the framework.

Phase

Phases are a logical collection of interceptors. As shown in Figure 2, the interceptors within a phase are called sequentially.

Figure 2. An interceptor phase

Interceptors are linked together into phases.

The phases are linked together in an ordered list to form an interceptor chain and provide defined logical steps in the message processing procedure. For example, a group of interceptors in the RECEIVE phase of an inbound interceptor chain processes transport level details using the raw message data picked up from the wire.

There is, however, no enforcement of what can be done in any of the phases. It is recommended that interceptors within a phase adhere to tasks that are in the spirit of the phase.

The complete list of phases defined by Fuse Services Framework can be found in Appendix A.

Specifying a phase

Fuse Services Framework provides the org.apache.cxf.Phase class to use for specifying a phase. The class is a collection of constants. Each phase defined by Fuse Services Framework has a corresponding constant in the Phase class. For example, the RECEIVE phase is specified by the value Phase.RECEIVE.

Setting the phase

An interceptor's phase is set in the interceptor's constructor. The AbstractPhaseInterceptor class defines three constructors for instantiating an interceptor:

  • public AbstractPhaseInterceptor(String phase)—sets the phase of the interceptor to the specified phase and automatically sets the interceptor's id to the interceptor's class name.

    Tip

    This constructor will satisfy most use cases.

  • public AbstractPhaseInterceptor(String id, String phase)—sets the interceptor's id to the string passed in as the first parameter and the interceptor's phase to the second string.

  • public AbstractPhaseInterceptor(String phase, boolean uniqueId)—specifies if the interceptor should use a unique, system generated id. If the uniqueId parameter is true, the interceptor's id will be calculated by the system. If the uniqueId parameter is false the interceptor's id is set to the interceptor's class name.

The recommended way to set a custom interceptor's phase is to pass the phase to the AbstractPhaseInterceptor constructor using the super() method as shown in Example 3.

Example 3. Setting an interceptor's phase

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

public class StreamInterceptor extends AbstractPhaseInterceptor<Message>
 {

    public StreamInterceptor()
   {
     super(Phase.PRE_STREAM);
    }
}

The StreamInterceptor interceptor shown in Example 3 is placed into the PRE_STREAM phase.

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