genericservlet.java

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// GenericServlet - convenience class for Servlet implementors
//
// API based on documentation from JavaSoft.
//
// Copyright (C) 1996,1998 by Jef Poskanzer <[e-mail]>. 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.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
// ANY EXPRESS 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 AUTHOR OR 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.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/

package Acme.Serve.servlet;

import java.io.*;
import java.util.*;

/// Convenience class for Servlet implementors.
// <P>
// This is an abstract object that implements the Servlet interface.
// Servlet has to be an interface so that things that must inherit
// from another object, such as RMI, can also be Servlets.  However,
// most of the time a Servlet will not need to be anything else, and
// it will be somewhat more convenient to extend this class and just
// provide the service() routine.
// <P>
// This is taken from JavaSoft's Servlet API documentation.
// <P>
// <A HREF="/resources/classes/Acme/Serve/servlet/GenericServlet.java">Fetch the software.</A><BR>
// <A HREF="/resources/classes/Acme.tar.gz">Fetch the entire Acme package.</A>
// <P>
// @see Acme.Serve.servlet.Servlet

public abstract class GenericServlet implements Servlet
    {

    /// Methods a Servlet author might want to override.

    /// Returns a string containing information about the author, version, and
    // copyright of the servlet.
    public String getServletInfo()
	{
	return null;
	}

    /// Initializes the servlet.
    // This is called by the system when the servlet is first loaded.
    // @exception ServletException when an exception has occurred
    public void init() throws ServletException
	{
	}

    /// Services a single request from the client.
    // <P>
    // Note that the server only creates a single instance of your Servlet
    // subclass, and calls the service() method of that one instance multiple
    // times, possibly at the same time in different threads.  This is somewhat
    // unusual in the Java world.  The implication is that any instance
    // variables in your class behave more like class variables - they are
    // shared among multiple concurrent calls.  So, be careful.
    // @param req the servlet request
    // @param req the servlet response
    // @exception ServletException when a servlet exception has occurred
    // @exception IOException when an I/O exception has occurred
    public abstract void service( ServletRequest req, ServletResponse res ) throws ServletException, IOException;

    /// Destroys the servlet and cleans up whatever resources are being held.
    // This is called by the system when the servlet is being destroyed.
    public void destroy()
	{
	}


    /// The rest will not generally be overridden.

    private ServletConfig config;

    /// Initializes the servlet.
    // This is called by the system when the servlet is first loaded.
    // @param config servlet initialization information
    // @exception ServletException when an exception has occurred
    public void init( ServletConfig config ) throws ServletException
	{
	this.config = config;
	init();
	}

    /// Returns a servlet config object, which contains any initialization
    // parameters and startup configuration for this servlet.
    public ServletConfig getServletConfig()
	{
	return config;
	}

    /// Write information to the servlet log.
    // @param message the message to log
    public void log( String message )
	{
	getServletContext().log( message );
	}

    /// Returns the servlet context. The servlet context lets a servlet
    // access the environment of the server in which it is running.
    public ServletContext getServletContext()
	{
	return config.getServletContext();
	}

    /// Gets an initialization parameter of the servlet.
    // @param name the parameter name
    public String getInitParameter( String name )
	{
	return config.getInitParameter( name );
	}

    /// Gets a hash table of the initialization parameters of the servlet.
    // @param name the parameter name
    public Enumeration getInitParameterNames()
	{
	return config.getInitParameterNames();
	}

    }