/*

  * Copyright 1999-2001,2004 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.commons.workflow.web;

 import java.io.IOException;

 import java.util.EmptyStackException;

 import javax.servlet.RequestDispatcher;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 import org.apache.commons.workflow.Context;

 import org.apache.commons.workflow.StepException;

 import org.apache.commons.workflow.base.BaseStep;

 import org.apache.commons.workflow.util.WorkflowUtils;

 /**

  * <p>Perform a <code>RequestDispatcher.forward()</code> operation on the

  * specified context relative path, and tell our <code>Context</code> to

  * suspend execution until control is returned.</p>

  *

  * <p>Supported Attributes:</p>

  * <ul>

  * <li><strong>page</strong> - Context relative URL (starting with a slash)

  *     of the application resource to be forwarded to, or omitted to pop a

  *     computed String value from the top of the evaluation stack.</li>

  * </ul>

  *

  * @version $Revision: 155475 $ $Date: 2005-02-26 13:31:11 +0000 (Sat, 26 Feb 2005) $

  * @author Craig R. McClanahan

  */

 public class ForwardStep extends BaseStep {

     // ----------------------------------------------------------= Constructors

     /**

      * Construct a default instance of this Step.

      */

     public ForwardStep() {

         super();

     }

     /**

      * Construct an instance of this Step with the specified identifier.

      *

      * @param id Step identifier

      */

     public ForwardStep(String id) {

         super();

         setId(id);

     }

     /**

      * Construct a fully configured instance of this Step.

      *

      * @param id Step identifier

      * @param page Context-relative url

      */

     public ForwardStep(String id, String page) {

         super();

         setId(id);

         setPage(page);

     }

     // ------------------------------------------------------------- Properties

     /**

      * The context-relative URL (starting with '/') of the resource to be

      * forwarded to.

      */

     protected String page = null;

     public String getPage() {

         return (this.page);

     }

     public void setPage(String page) {

         this.page = page;

     }

     // --------------------------------------------------------- Public Methods

     /**

      * Perform the executable actions related to this Step, in the context of

      * the specified Context.

      *

      * @param context The Context that is tracking our execution state

      *

      * @exception StepException if a processing error has occurred

      */

     public void execute(Context context) throws StepException {

         // Make sure our executing Context is a WebContext

         if (!(context instanceof WebContext))

             throw new StepException("Execution context is not a WebContext",

                                     this);

         WebContext webContext = (WebContext) context;

         // Get the actual resource reference we will be using

         String resource = page;

         if (resource == null) {

             try {

                 resource = (String) webContext.pop();

             } catch (EmptyStackException e) {

                 throw new StepException("Evaluation stack is empty", this);

             }

         }

         // Create a request dispatcher for this resource

         RequestDispatcher rd =

             webContext.getServletContext().getRequestDispatcher(resource);

         if (rd == null)

             throw new StepException("No request dispatcher for '" +

                                     resource + "'", this);

         ServletRequest request = webContext.getServletRequest();

         ServletResponse response = webContext.getServletResponse();

         // Forward to the requested resource

         try {

             rd.forward(request, response);

         } catch (IOException e) {

             throw new StepException("IOException forwarding to '" +

                                     resource + "'", e, this);

         } catch (ServletException e) {

             throw new StepException("ServletException forwarding to '" +

                                     resource + "'", e, this);

         }

         // Signal our Context to suspend execution

         context.setSuspend(true);

     }

     /**

      * Render a string representation of this Step.

      */

     public String toString() {

         StringBuffer sb = new StringBuffer("<web:forward");

         if (getId() != null) {

             sb.append(" id=\"");

             sb.append(getId());

             sb.append("\"");

         }

         sb.append(" page=\"");

         sb.append(getPage());

         sb.append("\"/>");

         return (sb.toString());

     }

 }