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ControllerServlet.java

package org.apache.velocity.demo;

/*
 * 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.
 */ 

// Java stuff
import java.util.*;
import java.io.StringWriter;
import java.io.PrintWriter;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.io.FileInputStream;

// Servlet stuff
import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

// Velocity stuff
import org.apache.velocity.context.Context;
import org.apache.velocity.Template;
import org.apache.velocity.servlet.VelocityServlet;

import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.exception.MethodInvocationException;

// Demo stuff
import org.apache.velocity.demo.action.*;

/**
 * Main entry point into the forum application.
 * All requests are made to this servlet.
 * 
 * @author <a href="mailto:daveb@miceda-data.com">Dave Bryson</a>
 * @version $Revision: 1.4.12.1 $
 * $Id: ControllerServlet.java,v 1.4.12.1 2004/03/04 00:18:29 geirm Exp $
 */
00054 public class ControllerServlet extends VelocityServlet
{
    private static String ERR_MSG_TAG = "forumdemo_current_error_msg";

    
    /**
     *  lets override the loadConfiguration() so we can do some 
     *  fancier setup of the template path
     */
00063     protected Properties loadConfiguration(ServletConfig config )
        throws IOException, FileNotFoundException
    {
        String propsFile = config.getInitParameter(INIT_PROPS_KEY);
        
        /*
         *  now convert to an absolute path relative to the webapp root
         *  This will work in a decently implemented servlet 2.2 
         *  container like Tomcat.
         */

        if ( propsFile != null )
        {
            String realPath = getServletContext().getRealPath(propsFile);
        
            if ( realPath != null )
            {
                propsFile = realPath;
            }
        }
        
       Properties p = new Properties(); 
       p.load( new FileInputStream(propsFile) );
      

       /*
        *  now, lets get the two elements we care about, the 
        *  template path and the log, and fix those from relative
        *  to the webapp root, to absolute on the filesystem, which is
        *  what velocity needs
        */

       String path = p.getProperty("file.resource.loader.path");

       if (path != null)
       {
           path = getServletContext().getRealPath( path );
           p.setProperty( "file.resource.loader.path", path );
       }
        
       path = p.getProperty("runtime.log");

       if (path != null)
       {
           path = getServletContext().getRealPath( path );
           p.setProperty("runtime.log", path );
       }

       return p;
    }

    /**
     * VelocityServlet handles most of the Servlet issues.
     * By extending it, you need to just implement the handleRequest method.
     * @param the Context created in VelocityServlet.
     * @return the template
     */
00120     public Template handleRequest( Context ctx )
    {
        HttpServletRequest req = (HttpServletRequest)ctx.get(VelocityServlet.REQUEST);
        HttpServletResponse resp = (HttpServletResponse)ctx.get(VelocityServlet.RESPONSE);
        Template template = null;
        String templateName = null;
        
        HttpSession sess = req.getSession();
        sess.setAttribute(ERR_MSG_TAG, "all ok" );

        try
        {
            // Process the command
            templateName = processRequest( req, resp, ctx );
            // Get the template
            template  = getTemplate( templateName );
        }
        catch( ResourceNotFoundException rnfe )
        {
            String err = "ForumDemo -> ControllerServlet.handleRequest() : Cannot find template " + templateName ;
            sess.setAttribute( ERR_MSG_TAG, err );
            System.out.println(err );
        }
        catch( ParseErrorException pee )
        {
            String err = "ForumDemo -> ControllerServlet.handleRequest() : Syntax error in template " + templateName + ":" + pee ;
            sess.setAttribute( ERR_MSG_TAG, err );
            System.out.println(err );
        }
        catch( Exception e )
        {
            String err = "Error handling the request: " + e ;
            sess.setAttribute( ERR_MSG_TAG, err );
            System.out.println(err );
        }

        return template;
    }
    
    /**
     * Process the request and execute the command.
     * Uses a command pattern
     * @param the request
     * @param the response 
     * @param the context
     * @return the name of the template to use
     */
00167     private String processRequest( HttpServletRequest req, HttpServletResponse resp, Context context )
     throws Exception
    {
        Command c = null;
        String template = null;
        String name = req.getParameter("action");
        
        if ( name == null || name.length() == 0 )
        {
            throw new Exception("Unrecognized action request!");
        }
                
        if ( name.equalsIgnoreCase("list") )
        {
            c = new ListCommand( req, resp);
            template = c.exec( context );
        }
        else if ( name.equalsIgnoreCase("post") ) 
        {
            c = new PostCommand( req, resp );
            template = c.exec( context ); 
        }
        else if (  name.equalsIgnoreCase("reply") )
        {
            c = new ReplyCommand( req, resp );
            template = c.exec( context );
        }
        else if (  name.equalsIgnoreCase("postreply") )
        {
            c = new PostReplyCommand( req, resp );
            template = c.exec( context );
        }
        else if ( name.equalsIgnoreCase("view") )
        {
            c = new ViewCommand( req, resp );
            template = c.exec( context );
        }
        return template;
    }

    /**
     *  Override the method from VelocityServlet to produce an intelligent 
     *  message to the browser
     */
00211     protected  void error( HttpServletRequest request, HttpServletResponse response, Exception cause )
        throws ServletException, IOException
    {
        HttpSession sess = request.getSession();
        String err = (String) sess.getAttribute( ERR_MSG_TAG );

        StringBuffer html = new StringBuffer();
        html.append("<html>");
        html.append("<body bgcolor=\"#ffffff\">");
        html.append("<h2>ForumDemo : Error processing the request</h2>");
        html.append("<br><br>There was a problem in the request." );
        html.append("<br><br>The relevant error is :<br>");
        html.append( err );
        html.append("<br><br><br>");
        html.append("The error occurred at :<br><br>");

        StringWriter sw = new StringWriter();
        cause.printStackTrace( new PrintWriter( sw ) );

        html.append( sw.toString()  );
        html.append("</body>");
        html.append("</html>");
        response.getOutputStream().print( html.toString() );
    }
}






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