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/**
*
* Copyright 2005 The Apache Software Foundation or its licensors, as applicable.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.tuscany.core.wire;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
/**
* Contains a source- or target-side invocation pipeline for a service operation. The runtime framework creates invocation chains
* on a per-operation, per-service basis. Further, invocation chains are further distinguished by being part of the source or
* target sides of a wire. Chains are "bridged" together by the runtime by a set of {@link
* org.apache.tuscany.core.builder.WireBuilder}s with the source-side holding references to the target.
* <p/>
* <code>InvocationChain</code>s are managed by {@link WireConfiguration}s, which are used by {@link
* org.apache.tuscany.core.wire.WireFactory}s to buildSource wires and proxies.
* <p/>
* Invocation configurations must contain at least one interceptor and may have 0 to N handlers. Handlers process a wire request
* or response in a one-way fashion. A typical wire sequence where interceptors and handlers are configured for both the source
* and target-side will proceed as follows:
* <pre>
* <ol>
* <li>The first source interceptor will be called with a message, which will in
* turn invoke the next interceptor in the chain <li>The last source interceptor, which must be of type {@link
* org.apache.tuscany.core.wire.impl.RequestResponseInterceptor} if there are handlers present, will be invoked. The RR
* interceptor will in turn pass the message to a {@link MessageChannel} which will invoke all source-side request handlers.
* <li>The RR interceptor will then invoke the target-side request <code>MessageChannel</code>.
* <li>The last source-side handler, an instance of {@link org.apache.tuscany.core.wire.impl.MessageDispatcher}, will invoke the
* first source-side interceptor, which in turn will pass the message down the target-side interceptor chain.
* <li>If the target is a component instance the last target-side interceptor, an instance of
* {@link org.apache.tuscany.core.wire.impl.InvokerInterceptor} will retrieve the {@link TargetInvoker} from the message and
* call it to invoke the operation on a target instance. <tt>TargetInvoker</tt>s are help by
* the source proxy to enable optimizations such as caching of target instances. <li> The response is returned up the wire
* stack
* until it reaches the source-side <tt>RequestResponseInterceptor</tt>, which invokes the target and source-side response
* channels respectively.
* <li>The response is then passed back up the rest of the wire stack. </ol>
* </pre>
* <p/>
* The source-to-target bridge may be constructed in any of the following ways:
* <pre>
* <ul>
* <li>Source handler-to-target handler
* <li>Source handler-to-target interceptor
* <li>Source interceptor-to-target handler
* <li>Source interceptor-to-target interceptor
* </ul>
* </pre>
* <p/>
* In some scenarios, a service proxy may only contain target-side invocaton chains, for example, when a service is resolved
* through a locate operation by a non-component client. In this case, there will be no source-side wire chains and the target
* invoker will be held by the target-side and passed down the pipeline.
*
* @version $Rev$ $Date$
* @see org.apache.tuscany.core.builder.WireBuilder
* @see WireFactory
* @see TargetInvoker
* @see org.apache.tuscany.core.wire.impl.MessageDispatcher
*/
public abstract class InvocationConfiguration {
// the operation on the target that will utlimately be invoked
protected Method operation;
// responsible for invoking a target instance
protected TargetInvoker targetInvoker;
protected Interceptor interceptorChainHead;
protected Interceptor interceptorChainTail;
protected List<MessageHandler> requestHandlers;
protected List<MessageHandler> responseHandlers;
public InvocationConfiguration(Method operation) {
assert (operation != null) : "No operation type specified";
this.operation = operation;
}
/**
* Returns the target operation for this invocation chain
*/
public Method getMethod() {
return operation;
}
/**
* Adds an request handler to the invocation chain
*/
public void addRequestHandler(MessageHandler handler) {
if (requestHandlers == null) {
requestHandlers = new ArrayList<MessageHandler>();
}
requestHandlers.add(handler);
}
/**
* Adds an response handler to the invocation chain
*/
public void addResponseHandler(MessageHandler handler) {
if (responseHandlers == null) {
responseHandlers = new ArrayList<MessageHandler>();
}
responseHandlers.add(handler);
}
/**
* Returns the request handler chain
*/
public List<MessageHandler> getRequestHandlers() {
return requestHandlers;
}
/**
* Returns the response handler chain
*/
public List<MessageHandler> getResponseHandlers() {
return responseHandlers;
}
/**
* Sets the target invoker to pass down the chain
*/
public void setTargetInvoker(TargetInvoker invoker) {
this.targetInvoker = invoker;
}
/**
* Returns the target invoker that is passed down the chain
*/
public TargetInvoker getTargetInvoker() {
return targetInvoker;
}
/**
* Adds an interceptor to the chain
*/
public void addInterceptor(Interceptor interceptor) {
if (interceptorChainHead == null) {
interceptorChainHead = interceptor;
} else {
interceptorChainTail.setNext(interceptor);
}
interceptorChainTail = interceptor;
}
/**
* Returns the last interceptor in the chain
*/
public Interceptor getTailInterceptor() {
return interceptorChainTail;
}
/**
* Returns the first interceptor in the chain
*/
public Interceptor getHeadInterceptor() {
return interceptorChainHead;
}
/**
* Signals to the chain that its configuration is complete. Implementations may use this callback to prepare there invocation
* chains.
*/
public abstract void build();
}
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