001 /*
002 * Copyright 1999-2001,2004 The Apache Software Foundation.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package org.apache.commons.workflow.web;
018
019
020 import java.io.IOException;
021 import java.util.EmptyStackException;
022 import javax.servlet.RequestDispatcher;
023 import javax.servlet.ServletException;
024 import javax.servlet.ServletRequest;
025 import javax.servlet.ServletResponse;
026 import org.apache.commons.workflow.Context;
027 import org.apache.commons.workflow.StepException;
028 import org.apache.commons.workflow.base.BaseStep;
029 import org.apache.commons.workflow.util.WorkflowUtils;
030
031
032 /**
033 * <p>Perform a <code>RequestDispatcher.forward()</code> operation on the
034 * specified context relative path, and tell our <code>Context</code> to
035 * suspend execution until control is returned.</p>
036 *
037 * <p>Supported Attributes:</p>
038 * <ul>
039 * <li><strong>page</strong> - Context relative URL (starting with a slash)
040 * of the application resource to be forwarded to, or omitted to pop a
041 * computed String value from the top of the evaluation stack.</li>
042 * </ul>
043 *
044 * @version $Revision: 155475 $ $Date: 2005-02-26 13:31:11 +0000 (Sat, 26 Feb 2005) $
045 * @author Craig R. McClanahan
046 */
047
048 public class ForwardStep extends BaseStep {
049
050
051 // ----------------------------------------------------------= Constructors
052
053
054 /**
055 * Construct a default instance of this Step.
056 */
057 public ForwardStep() {
058
059 super();
060
061 }
062
063
064 /**
065 * Construct an instance of this Step with the specified identifier.
066 *
067 * @param id Step identifier
068 */
069 public ForwardStep(String id) {
070
071 super();
072 setId(id);
073
074 }
075
076
077 /**
078 * Construct a fully configured instance of this Step.
079 *
080 * @param id Step identifier
081 * @param page Context-relative url
082 */
083 public ForwardStep(String id, String page) {
084
085 super();
086 setId(id);
087 setPage(page);
088
089 }
090
091
092 // ------------------------------------------------------------- Properties
093
094
095 /**
096 * The context-relative URL (starting with '/') of the resource to be
097 * forwarded to.
098 */
099 protected String page = null;
100
101 public String getPage() {
102 return (this.page);
103 }
104
105 public void setPage(String page) {
106 this.page = page;
107 }
108
109
110 // --------------------------------------------------------- Public Methods
111
112
113 /**
114 * Perform the executable actions related to this Step, in the context of
115 * the specified Context.
116 *
117 * @param context The Context that is tracking our execution state
118 *
119 * @exception StepException if a processing error has occurred
120 */
121 public void execute(Context context) throws StepException {
122
123 // Make sure our executing Context is a WebContext
124 if (!(context instanceof WebContext))
125 throw new StepException("Execution context is not a WebContext",
126 this);
127 WebContext webContext = (WebContext) context;
128
129 // Get the actual resource reference we will be using
130 String resource = page;
131 if (resource == null) {
132 try {
133 resource = (String) webContext.pop();
134 } catch (EmptyStackException e) {
135 throw new StepException("Evaluation stack is empty", this);
136 }
137 }
138
139 // Create a request dispatcher for this resource
140 RequestDispatcher rd =
141 webContext.getServletContext().getRequestDispatcher(resource);
142 if (rd == null)
143 throw new StepException("No request dispatcher for '" +
144 resource + "'", this);
145 ServletRequest request = webContext.getServletRequest();
146 ServletResponse response = webContext.getServletResponse();
147
148 // Forward to the requested resource
149 try {
150 rd.forward(request, response);
151 } catch (IOException e) {
152 throw new StepException("IOException forwarding to '" +
153 resource + "'", e, this);
154 } catch (ServletException e) {
155 throw new StepException("ServletException forwarding to '" +
156 resource + "'", e, this);
157 }
158
159 // Signal our Context to suspend execution
160 context.setSuspend(true);
161
162 }
163
164
165 /**
166 * Render a string representation of this Step.
167 */
168 public String toString() {
169
170 StringBuffer sb = new StringBuffer("<web:forward");
171 if (getId() != null) {
172 sb.append(" id=\"");
173 sb.append(getId());
174 sb.append("\"");
175 }
176 sb.append(" page=\"");
177 sb.append(getPage());
178 sb.append("\"/>");
179 return (sb.toString());
180
181 }
182
183
184 }