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/*
 * Copyright 2004-2008 the original author or authors.
 *
 * 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.springframework.webflow.action;

import org.springframework.util.Assert;
import org.springframework.webflow.execution.Event;
import org.springframework.webflow.execution.RequestContext;

/**
 * Action implementation that bundles two or more action execution methods into a single class. Action execution methods
 * defined by subclasses must adhere to the following signature:
 * 
 * 
 *     public Event ${method}(RequestContext context) throws Exception;
 * 
* * When this action is invoked, by default the id of the calling action state state is treated as the * action execution method name. Alternatively, the execution method name may be explicitly specified as a attribute of * the calling action state. *

* For example, the following action state definition: * *

 *     <action-state id="search">
 *         <evaluate expression="searchAction.executeSearch"/>
 *         <transition on="success" to="results"/>
 *     </action-state>
 * 
* * ... when entered, executes the method: * *
 * public Event search(RequestContext context) throws Exception;
 * 
* *

* One use of the MultiAction is to centralize all command logic for a flow in one place. Another use is to centralize * form setup and submit logic in one place, or CRUD (create/read/update/delete) operations for a single domain object * in one place. * * @see MultiAction.MethodResolver * @see org.springframework.webflow.action.DefaultMultiActionMethodResolver * * @author Keith Donald * @author Erwin Vervaet */ public class MultiAction extends AbstractAction { /** * A cache for dispatched action execute methods. The default signature is * public Event ${method}(RequestContext context) throws Exception;. */ private DispatchMethodInvoker methodInvoker; /** * The action method resolver strategy. */ private MethodResolver methodResolver = new DefaultMultiActionMethodResolver(); /** * Protected default constructor; not invokable for direct MultiAction instantiation. Intended for use by * subclasses. *

* Sets the target to this multi action instance. * @see #setTarget(Object) */ protected MultiAction() { setTarget(this); } /** * Constructs a multi action that invokes methods on the specified target object. Note: invokable methods on the * target must conform to the multi action method signature: * *

	 *       public Event ${method}(RequestContext context) throws Exception;
	 * 
* * @param target the target of this multi action's invocations */ public MultiAction(Object target) { setTarget(target); } /** * Sets the target of this multi action's invocations. * @param target the target */ protected final void setTarget(Object target) { methodInvoker = new DispatchMethodInvoker(target, new Class[] { RequestContext.class }); } /** * Get the strategy used to resolve action execution method names. */ public MethodResolver getMethodResolver() { return methodResolver; } /** * Set the strategy used to resolve action execution method names. Allows full control over the method resolution * algorithm. Defaults to {@link DefaultMultiActionMethodResolver}. */ public void setMethodResolver(MethodResolver methodResolver) { this.methodResolver = methodResolver; } protected final Event doExecute(RequestContext context) throws Exception { String method = getMethodResolver().resolveMethod(context); Object obj = methodInvoker.invoke(method, new Object[] { context }); if (obj != null) { Assert.isInstanceOf(Event.class, obj, "The '" + method + "' action execution method on target object '" + methodInvoker.getTarget() + "' did not return an Event object but '" + obj + "' of type " + obj.getClass().getName() + " -- " + "Programmer error; make sure the method signature conforms to " + "'public Event ${method}(RequestContext context) throws Exception;'."); } return (Event) obj; } /** * Strategy interface used by the MultiAction to map a request context to the name of an action execution method. * * @author Keith Donald * @author Erwin Vervaet */ public interface MethodResolver { /** * Resolve a method name from given flow execution request context. * @param context the flow execution request context * @return the name of the method that should handle action execution */ public String resolveMethod(RequestContext context); } }




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