AbstractHandler.java

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//  Copyright (c) 1995-2017 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
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//  You may elect to redistribute this code under either of these licenses.
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package org.eclipse.jetty.server.handler;


import java.io.IOException;

import javax.servlet.DispatcherType;
import javax.servlet.RequestDispatcher;
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.HttpChannel;
import org.eclipse.jetty.server.HttpConnection;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Response;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.util.annotation.ManagedObject;
import org.eclipse.jetty.util.component.ContainerLifeCycle;
import org.eclipse.jetty.util.component.Dumpable;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;


/** AbstractHandler.
 * <p>A convenience implementation of {@link Handler} that uses the 
 * {@link ContainerLifeCycle} to provide:<ul>
 * <li>start/stop behavior
 * <li>a bean container
 * <li>basic {@link Dumpable} support
 * <li>a {@link Server} reference
 * <li>optional error dispatch handling
 * </ul>
 */
@ManagedObject("Jetty Handler")
public abstract class AbstractHandler extends ContainerLifeCycle implements Handler
{
    private static final Logger LOG = Log.getLogger(AbstractHandler.class);

    private Server _server;
    
    /**
     * 
     */
    public AbstractHandler()
    {
    }
    
    @Override
    public abstract void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException;

    /**
     * Convenience method to generate error page.
     * <p>This method can be called from {@link #handle(String, Request, HttpServletRequest, HttpServletResponse)} when an {@link DispatcherType#ERROR} dispatch
     * is detected and an error page needs to be generated by calling {@link HttpServletResponse#sendError(int, String)} with the appropriate code and reason,
     * which are taken from {@link HttpServletRequest#getAttribute(String)} for {@link RequestDispatcher#ERROR_STATUS_CODE} and {@link RequestDispatcher#ERROR_MESSAGE}
     * @see ErrorDispatchHandler for a conveniance class that calls this method.
     * @param target
     *            The target of the request - either a URI or a name.
     * @param baseRequest
     *            The original unwrapped request object.
     * @param request
     *            The request either as the {@link Request} object or a wrapper of that request. The
     *            <code>{@link HttpConnection#getCurrentConnection()}.{@link HttpConnection#getHttpChannel() getHttpChannel()}.{@link HttpChannel#getRequest() getRequest()}</code>
     *            method can be used access the Request object if required.
     * @param response
     *            The response as the {@link Response} object or a wrapper of that request. The
     *            <code>{@link HttpConnection#getCurrentConnection()}.{@link HttpConnection#getHttpChannel() getHttpChannel()}.{@link HttpChannel#getResponse() getResponse()}</code>
     *            method can be used access the Response object if required.
     * @throws IOException
     *             if unable to handle the request or response processing
     * @throws ServletException
     *             if unable to handle the request or response due to underlying servlet issue
     */
    protected void doError(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        Object o = request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
        int code = (o instanceof Integer)?((Integer)o).intValue():(o!=null?Integer.valueOf(o.toString()):500);
        o = request.getAttribute(RequestDispatcher.ERROR_MESSAGE);
        String reason = o!=null?o.toString():null;
        
        response.sendError(code,reason);
    }
    
    /* 
     * @see org.eclipse.thread.LifeCycle#start()
     */
    @Override
    protected void doStart() throws Exception
    {
        if (LOG.isDebugEnabled())
            LOG.debug("starting {}",this);
        if (_server==null)
            LOG.warn("No Server set for {}",this);
        super.doStart();
    }

    /* 
     * @see org.eclipse.thread.LifeCycle#stop()
     */
    @Override
    protected void doStop() throws Exception
    {
        if (LOG.isDebugEnabled())
            LOG.debug("stopping {}",this);
        super.doStop();
    }

    @Override
    public void setServer(Server server)
    {
        if (_server==server)
            return;
        if (isStarted())
            throw new IllegalStateException(STARTED);
        _server=server;
    }

    @Override
    public Server getServer()
    {
        return _server;
    }

    @Override
    public void destroy()
    {
        if (!isStopped())
            throw new IllegalStateException("!STOPPED");
        super.destroy();
    }

    @Override
    public void dumpThis(Appendable out) throws IOException
    {
        out.append(toString()).append(" - ").append(getState()).append('\n');
    }

    /**
     * An extension of AbstractHandler that handles {@link DispatcherType#ERROR} dispatches.
     * <p>
     * {@link DispatcherType#ERROR} dispatches are handled by calling the {@link #doError(String, Request, HttpServletRequest, HttpServletResponse)}
     * method.  All other dispatches are passed to the abstract {@link #doNonErrorHandle(String, Request, HttpServletRequest, HttpServletResponse)}
     * method, which should be implemented with specific handler behavior 
     *
     */
    public static abstract class ErrorDispatchHandler extends AbstractHandler
    {
        @Override
        public final void handle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
        {
            if (baseRequest.getDispatcherType()==DispatcherType.ERROR)
                doError(target,baseRequest,request,response);
            else
                doNonErrorHandle(target,baseRequest,request,response);
        }

        /**
         * Called by {@link #handle(String, Request, HttpServletRequest, HttpServletResponse)} 
         * for all non-{@link DispatcherType#ERROR} dispatches.
         * @param target
         *            The target of the request - either a URI or a name.
         * @param baseRequest
         *            The original unwrapped request object.
         * @param request
         *            The request either as the {@link Request} object or a wrapper of that request. The
         *            <code>{@link HttpConnection#getCurrentConnection()}.{@link HttpConnection#getHttpChannel() getHttpChannel()}.{@link HttpChannel#getRequest() getRequest()}</code>
         *            method can be used access the Request object if required.
         * @param response
         *            The response as the {@link Response} object or a wrapper of that request. The
         *            <code>{@link HttpConnection#getCurrentConnection()}.{@link HttpConnection#getHttpChannel() getHttpChannel()}.{@link HttpChannel#getResponse() getResponse()}</code>
         *            method can be used access the Response object if required.
         * @throws IOException
         *             if unable to handle the request or response processing
         * @throws ServletException
         *             if unable to handle the request or response due to underlying servlet issue
         */
        protected abstract void doNonErrorHandle(String target, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException;
    }

}