//
// ========================================================================
// Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.embedded;
import java.io.File;
import java.io.IOException;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.eclipse.jetty.server.Handler;
import org.eclipse.jetty.server.NCSARequestLog;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.AbstractHandler;
import org.eclipse.jetty.server.handler.DefaultHandler;
import org.eclipse.jetty.server.handler.HandlerCollection;
import org.eclipse.jetty.server.handler.HandlerList;
import org.eclipse.jetty.server.handler.HandlerWrapper;
import org.eclipse.jetty.server.handler.RequestLogHandler;
import org.eclipse.jetty.util.ajax.JSON;
/**
* Frequently many handlers are combined together to handle different aspects of
* a request. A handler may:
* <ul>
* <li>handle the request and completely generate the response
* <li>partially handle the request, but defer response generation to another
* handler.
* <li>select another handler to pass the request to.
* <li>use business logic to decide to do one of the above.
* </ul>
* Multiple handlers may be combined with:
* <ul>
* <li>{@link HandlerWrapper} which will nest one handler inside another. In
* this example, the HelloHandler is nested inside a HandlerWrapper that sets
* the greeting as a request attribute.
* <li>{@link HandlerList} which will call a collection of handlers until the
* request is marked as handled. In this example, a list is used to combine the
* param handler (which only handles the request if there are parameters) and
* the wrapper handler. Frequently handler lists are terminated with the
* {@link DefaultHandler}, which will generate a suitable 404 response if the
* request has not been handled.
* <li>{@link HandlerCollection} which will call each handler regardless if the
* request has been handled or not. Typically this is used to always pass a
* request to the logging handler.
* </ul>
*/
public class ManyHandlers
{
/**
* Produce output that lists all of the request parameters
*/
public static class ParamHandler extends AbstractHandler
{
public void handle( String target,
Request baseRequest,
HttpServletRequest request,
HttpServletResponse response ) throws IOException,
ServletException
{
Map<String, String[]> params = request.getParameterMap();
if (params.size() > 0)
{
response.setContentType("text/plain");
response.getWriter().println(JSON.toString(params));
baseRequest.setHandled(true);
}
}
}
/**
* Add a request attribute, but produce no output.
*/
public static class WelcomeWrapHandler extends HandlerWrapper
{
@Override
public void handle( String target,
Request baseRequest,
HttpServletRequest request,
HttpServletResponse response ) throws IOException,
ServletException
{
request.setAttribute("welcome", "Hello");
super.handle(target, baseRequest, request, response);
}
}
public static void main( String[] args ) throws Exception
{
Server server = new Server(8080);
// create the handlers
Handler param = new ParamHandler();
HandlerWrapper wrapper = new WelcomeWrapHandler();
Handler hello = new HelloHandler();
Handler dft = new DefaultHandler();
RequestLogHandler requestLog = new RequestLogHandler();
// configure request logging
File requestLogFile = File.createTempFile("demo", "log");
NCSARequestLog ncsaLog = new NCSARequestLog(
requestLogFile.getAbsolutePath());
requestLog.setRequestLog(ncsaLog);
// create the handler collections
HandlerCollection handlers = new HandlerCollection();
HandlerList list = new HandlerList();
// link them all together
wrapper.setHandler(hello);
list.setHandlers(new Handler[] { param, wrapper, dft });
handlers.setHandlers(new Handler[] { list, requestLog });
// Handler tree looks like the following
// <pre>
// Server
// + HandlerCollection
// . + HandlerList
// . | + param (ParamHandler)
// . | + wrapper (WelcomeWrapHandler)
// . | | \ hello (HelloHandler)
// . | \ dft (DefaultHandler)
// . \ requestLog (RequestLogHandler)
// </pre>
server.setHandler(handlers);
server.start();
server.join();
}
}