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Posted to dev@velocity.apache.org by ge...@apache.org on 2001/02/05 07:15:40 UTC
cvs commit: jakarta-velocity/whiteboard/geir VelocityServlet.java
geirm 01/02/04 22:15:40
Added: whiteboard/geir VelocityServlet.java
Log:
For review.... implemented some of Christoph's ideas...
Revision Changes Path
1.1 jakarta-velocity/whiteboard/geir/VelocityServlet.java
Index: VelocityServlet.java
===================================================================
package org.apache.velocity.servlet;
/*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Velocity", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
* nor may "Apache" appear in their names without prior written
* permission of the Apache Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.util.Stack;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletResponse;
import org.apache.velocity.Template;
import org.apache.velocity.runtime.Runtime;
import org.apache.velocity.io.VelocityWriter;
import org.apache.velocity.util.SimplePool;
import org.apache.velocity.context.Context;
import org.apache.velocity.VelocityContext;
/**
* Base class which simplifies the use of Velocity with Servlets.
* Extend this class, implement the <code>handleRequest()</code> method,
* and add your data to the context. Then call
* <code>getTemplate("myTemplate.wm")</code>.
*
* This class puts some things into the context object that you should
* be aware of:
* <pre>
* "req" - The HttpServletRequest object
* "res" - The HttpServletResponse object
* </pre>
*
* If you put a contentType object into the context within either your
* serlvet or within your template, then that will be used to override
* the default content type specified in the properties file.
*
* "contentType" - The value for the Content-Type: header
*
* @author Dave Bryson
* @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
* @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
* $Id: VelocityServlet.java,v 1.1 2001/02/05 06:15:40 geirm Exp $
*/
public abstract class VelocityServlet extends HttpServlet
{
/**
* The HTTP request object context key.
*/
public static final String REQUEST = "req";
/**
* The HTTP response object context key.
*/
public static final String RESPONSE = "res";
/**
* The HTTP content type context key.
*/
public static final String CONTENT_TYPE = "contentType";
/**
* The encoding to use when generating outputing.
*/
private static String encoding = null;
/**
* The default content type.
*/
private static String defaultContentType;
/**
* This is the string that is looked for when getInitParameter is
* called.
*/
private static final String INIT_PROPS_KEY = "properties";
/**
* Cache of writers
*/
private static SimplePool writerPool = new SimplePool(40);
/**
* Performs initialization of this servlet. Called by the servlet
* container on loading.
*
* @param config The servlet configuration to apply.
*
* @exception ServletException
*/
public void init( ServletConfig config )
throws ServletException
{
super.init( config );
String propsFile = config.getInitParameter(INIT_PROPS_KEY);
/*
* This will attempt to find the location of the properties
* file from the relative path to the WAR archive (ie:
* docroot). Since JServ returns null for getRealPath()
* because it was never implemented correctly, then we know we
* will not have an issue with using it this way. I don't know
* if this will break other servlet engines, but it probably
* shouldn't since WAR files are the future anyways.
*/
if ( propsFile != null )
{
String realPath = getServletContext().getRealPath(propsFile);
if ( realPath != null )
{
propsFile = realPath;
}
}
try
{
Runtime.init(propsFile);
defaultContentType =
Runtime.getString(Runtime.DEFAULT_CONTENT_TYPE, "text/html");
encoding = Runtime.getString(Runtime.TEMPLATE_ENCODING, "8859_1");
}
catch( Exception e )
{
throw new ServletException("Error configuring the loader: " + e);
}
}
/**
* Handles GET
*/
public final void doGet( HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
doRequest(request, response);
}
/**
* Handle a POST
*/
public final void doPost( HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
doRequest(request, response);
}
/**
* Handles all requests
*
* @param request HttpServletRequest object containing client request
* @param response HttpServletResponse object for the response
*/
private void doRequest(HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
try
{
/*
* first, get a context
*/
Context context = createContext( request, response );
/*
* set the content type
*/
setContentType( response );
/*
* let someone handle the request
*/
Template template = handleRequest(context);
/*
* bail if we can't find the template
*/
if ( template == null )
{
throw new Exception ("Cannot find the template!" );
}
/*
* now merge it
*/
mergeTemplate( template, context, response );
}
catch (Exception e)
{
error ( response, e.getMessage());
}
}
/**
* merges the template with the context. Only override this if you really, really
* really need to. (And don't call us with questions if it breaks :)
*
* @param template template object returned by the handleRequest() method
* @param context context created by the createContext() method
* @param response servlet reponse (use this to get the output stream or Writer
*/
protected void mergeTemplate( Template template, Context context, HttpServletResponse response )
throws Exception
{
ServletOutputStream output = response.getOutputStream();
VelocityWriter vw = null;
try
{
vw = (VelocityWriter) writerPool.get();
if (vw == null)
{
vw = new VelocityWriter( new OutputStreamWriter(output, encoding), 4*1024, true);
}
else
{
vw.recycle(new OutputStreamWriter(output, encoding));
}
template.merge( context, vw);
}
finally
{
try
{
if (vw != null)
{
vw.flush();
writerPool.put(vw);
output.close();
}
}
catch (Exception e)
{
// do nothing
}
}
}
protected void setContentType( ServletResponse response )
{
response.setContentType( defaultContentType );
}
/**
* returns a context
*
*/
protected Context createContext(HttpServletRequest request, HttpServletResponse response )
{
/*
* create a new context
*/
VelocityContext context = new VelocityContext();
/*
* put the request/response objects into the context
*/
context.put( REQUEST, request );
context.put( RESPONSE, response );
return context;
}
/**
* Retrieves the requested template.
*
* @param name The file name of the template to retrieve relative to the
* <code>template.path</code> property.
* @return The requested template.
*/
public Template getTemplate( String name )
throws Exception
{
return Runtime.getTemplate(name);
}
/**
* Implement this method to add your application data to the context,
* calling the <code>getTemplate()</code> method to produce your return
* value.
*
* @param ctx The context to add your data to.
* @return The template to merge with your context.
*/
protected abstract Template handleRequest( Context ctx );
/**
* Send an error message to the client.
*/
private final void error( ServletResponse response, String message )
throws ServletException, IOException
{
StringBuffer html = new StringBuffer();
html.append("<html>");
html.append("<body bgcolor=\"#ffffff\">");
html.append("<h2>Error processing the template</h2>");
html.append(message);
html.append("</body>");
html.append("</html>");
response.getOutputStream().print( html.toString() );
}
}