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  /*
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   * The Apache Software License, Version 1.1
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   *
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   * Copyright (c) 1999 The Apache Software Foundation.  All rights 
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   * reserved.
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   *
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   * Redistribution and use in source and binary forms, with or without
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   * modification, are permitted provided that the following conditions
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   * are met:
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  *
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  * 1. Redistributions of source code must retain the above copyright
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  *    notice, this list of conditions and the following disclaimer. 
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  *
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  * 2. Redistributions in binary form must reproduce the above copyright
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  *    notice, this list of conditions and the following disclaimer in
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  *    the documentation and/or other materials provided with the
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  *    distribution.
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  *
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  * 3. The end-user documentation included with the redistribution, if
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  *    any, must include the following acknowlegement:  
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  *       "This product includes software developed by the 
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  *        Apache Software Foundation (http://www.apache.org/)."
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  *    Alternately, this acknowlegement may appear in the software itself,
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  *    if and wherever such third-party acknowlegements normally appear.
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  *
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  * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
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  *    Foundation" must not be used to endorse or promote products derived
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  *    from this software without prior written permission. For written 
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  *    permission, please contact apache@apache.org.
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  *
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  * 5. Products derived from this software may not be called "Apache"
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  *    nor may "Apache" appear in their names without prior written
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  *    permission of the Apache Group.
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  *
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  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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  * SUCH DAMAGE.
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  * ====================================================================
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  *
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  * This software consists of voluntary contributions made by many
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  * individuals on behalf of the Apache Software Foundation.  For more
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  * information on the Apache Software Foundation, please see
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  * <http://www.apache.org/>.
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  *
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  * ====================================================================
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  *
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  * This source code implements specifications defined by the Java
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  * Community Process. In order to remain compliant with the specification
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  * DO NOT add / change / or delete method signatures!
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  */ 
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 package javax.servlet;
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Defines methods that all servlets must implement.

A servlet is a small Java program that runs within a Web server. Servlets receive and respond to requests from Web clients, usually across HTTP, the HyperText Transfer Protocol.

To implement this interface, you can write a generic servlet that extends javax.servlet.GenericServlet or an HTTP servlet that extends javax.servlet.http.HttpServlet.

This interface defines methods to initialize a servlet, to service requests, and to remove a servlet from the server. These are known as life-cycle methods and are called in the following sequence:

  1. The servlet is constructed, then initialized with the init method.
  2. Any calls from clients to the service method are handled.
  3. The servlet is taken out of service, then destroyed with the destroy method, then garbage collected and finalized.

In addition to the life-cycle methods, this interface provides the getServletConfig method, which the servlet can use to get any startup information, and the getServletInfo method, which allows the servlet to return basic information about itself, such as author, version, and copyright.

Author(s):
Various
Version:
$Version$
See also:
GenericServlet
javax.servlet.http.HttpServlet
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public interface Servlet {

    
Called by the servlet container to indicate to a servlet that the servlet is being placed into service.

The servlet container calls the init method exactly once after instantiating the servlet. The init method must complete successfully before the servlet can receive any requests.

The servlet container cannot place the servlet into service if the init method

  1. Throws a ServletException
  2. Does not return within a time period defined by the Web server

Parameters:
config a ServletConfig object containing the servlet's configuration and initialization parameters
Throws:
ServletException if an exception has occurred that interferes with the servlet's normal operation
See also:
UnavailableException
getServletConfig()
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    public void init(ServletConfig config) throws ServletException;
    
    

    
Returns a ServletConfig object, which contains initialization and startup parameters for this servlet. The ServletConfig object returned is the one passed to the init method.

Implementations of this interface are responsible for storing the ServletConfig object so that this method can return it. The GenericServlet class, which implements this interface, already does this.

Returns:
the ServletConfig object that initializes this servlet
See also:
init(javax.servlet.ServletConfig)
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    public ServletConfig getServletConfig();
    
    

    
Called by the servlet container to allow the servlet to respond to a request.

This method is only called after the servlet's init() method has completed successfully.

Servlets typically run inside multithreaded servlet containers that can handle multiple requests concurrently. Developers must be aware to synchronize access to any shared resources such as files, network connections, and as well as the servlet's class and instance variables. More information on multithreaded programming in Java is available in the Java tutorial on multi-threaded programming.

Parameters:
req the ServletRequest object that contains the client's request
res the ServletResponse object that contains the servlet's response
Throws:
ServletException if an exception occurs that interferes with the servlet's normal operation
java.io.IOException if an input or output exception occurs
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    public void service(ServletRequest req, ServletResponse res)
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	throws ServletException, IOException;
	
	

    
Returns information about the servlet, such as author, version, and copyright.

The string that this method returns should be plain text and not markup of any kind (such as HTML, XML, etc.).

Returns:
a String containing servlet information
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    public String getServletInfo();
    
    

    
Called by the servlet container to indicate to a servlet that the servlet is being taken out of service. This method is only called once all threads within the servlet's service method have exited or after a timeout period has passed. After the servlet container calls this method, it will not call the service method again on this servlet.

This method gives the servlet an opportunity to clean up any resources that are being held (for example, memory, file handles, threads) and make sure that any persistent state is synchronized with the servlet's current state in memory. 

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    public void destroy();
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