/*
* Copyright 1999-2004 The Apache Software Foundation.
*
* 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.struts.chain.legacy;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.chain.Catalog;
import org.apache.commons.chain.CatalogFactory;
import org.apache.commons.chain.Command;
import org.apache.commons.chain.Context;
import org.apache.commons.chain.web.servlet.ServletWebContext;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
/**
* <p>An <code>Action</code> implementation that delegates to a
* configured Chain (or Command) for performing the actual business
* logic related to a request. The name of the chain to be executed
* is specified by setting the <code>parameter</code> attribute of
* the <code><action></code> element configuring this action.
* For example:</p>
*
* <pre>
* <action path="/myaction"
* type="org.apache.struts.chain.legacy.ChainAction"
* name="myform"
* scope="request"
* input="/mypage.jsp"
* parameter="name-of-chain-to-execute"
* </pre>
*
* <p>Prior to calling the specified chain (or command), this action
* sets up a <code>Context</code> object containing the relevant
* properties, along with the following additional attributes:</p>
* <ul>
* <li><strong>mapping</strong> - The <code>ActionMapping</code> passed
* to our <code>execute()</code> method</li>
* <li><strong>form</strong> - The <code>ActionForm</code> passed to
* our <code>execute()</code> method</li>
* </ul>
*
* <p>After execution of the specified command or chain is completed,
* the following context attributes are examined (in this order) to
* determine how to proceed.</p>
* <ul>
* <li><strong>exception</strong> - If a <code>java.lang.Exception</code>
* is found here, it will be rethrown as the outcome of this action.</li>
* <li><strong>forward</strong> - If an
* <code>org.apache.struts.action.ActionForward</code> is found here,
* it will be returned as the outcome of this action. Otherwise,
* <code>null</code> will be returned.</li>
* </ul>
*/
public class ChainAction extends Action {
// ------------------------------------------------------- Instance Varibles
/**
* <p>The <code>Catalog</code> that will be consulted to look up
* the <code>Command</code> to be executed.</p>
*/
private Catalog catalog = null;
// ---------------------------------------------------------- Public Methods
/**
* <p>Delegate to the command chain specified in our configuration.</p>
*
* @param mapping <code>ActionMapping</code> configuring this action
* @param form <code>ActionForm</code> for this request (if any)
* @param request <code>HttpServletRequest</code> we are processing
* @param response <code>HttpServletResponse</code> we are creating
*/
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
// Set up a context for this request
Context context = new ServletWebContext
(getServlet().getServletContext(), request, response);
context.put("mapping", mapping);
context.put("form", form);
// Delegate to the specified command
Command command = getCatalog().getCommand(mapping.getParameter());
command.execute(context); // Ignore return state
// Return results as appropriate
Exception exception = null;
try {
exception = (Exception) context.get("exception");
if (exception != null) {
throw exception;
}
} catch (ClassCastException e) {
; // It is not an Exception
}
ActionForward forward = null;
try {
forward = (ActionForward) context.get("forward");
} catch (ClassCastException e) {
forward = null; // It is not an ActionForward
}
return forward;
}
// ------------------------------------------------------- Protected Methods
/**
* <p>Return the <code>Catalog</code> we will use to acquire the
* <code>Command</code> to be executed. NOTE: Any race condition
* calling this method is harmless, so do not bother to synchronize.</p>
*/
protected Catalog getCatalog() {
if (catalog == null) {
catalog = CatalogFactory.getInstance().getCatalog();
}
return catalog;
}
}