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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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package jakarta.servlet;

import java.io.IOException;

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
jakarta.servlet.GenericServlet or an HTTP servlet that extends
jakarta.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:

The servlet is constructed, then initialized with the init
method.
Any calls from clients to the service method are handled.
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.
See Also:
GenericServlet
HttpServlet/**
 * Defines methods that all servlets must implement.
 *
 * <p>
 * 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.
 *
 * <p>
 * To implement this interface, you can write a generic servlet that extends
 * <code>jakarta.servlet.GenericServlet</code> or an HTTP servlet that extends
 * <code>jakarta.servlet.http.HttpServlet</code>.
 *
 * <p>
 * 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:
 * <ol>
 * <li>The servlet is constructed, then initialized with the <code>init</code>
 * method.
 * <li>Any calls from clients to the <code>service</code> method are handled.
 * <li>The servlet is taken out of service, then destroyed with the
 * <code>destroy</code> method, then garbage collected and finalized.
 * </ol>
 *
 * <p>
 * In addition to the life-cycle methods, this interface provides the
 * <code>getServletConfig</code> method, which the servlet can use to get any
 * startup information, and the <code>getServletInfo</code> method, which allows
 * the servlet to return basic information about itself, such as author,
 * version, and copyright.
 *
 * @see GenericServlet
 * @see jakarta.servlet.http.HttpServlet
 */
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

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

Params:
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/**
     * Called by the servlet container to indicate to a servlet that the servlet
     * is being placed into service.
     *
     * <p>
     * The servlet container calls the <code>init</code> method exactly once
     * after instantiating the servlet. The <code>init</code> method must
     * complete successfully before the servlet can receive any requests.
     *
     * <p>
     * The servlet container cannot place the servlet into service if the
     * <code>init</code> method
     * <ol>
     * <li>Throws a <code>ServletException</code>
     * <li>Does not return within a time period defined by the Web server
     * </ol>
     *
     *
     * @param config
     *            a <code>ServletConfig</code> object containing the servlet's
     *            configuration and initialization parameters
     *
     * @exception ServletException
     *                if an exception has occurred that interferes with the
     *                servlet's normal operation
     *
     * @see UnavailableException
     * @see #getServletConfig
     */
    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. 
See Also:
init
Returns:
the ServletConfig object that initializes this
        servlet/**
     *
     * Returns a {@link ServletConfig} object, which contains initialization and
     * startup parameters for this servlet. The <code>ServletConfig</code>
     * object returned is the one passed to the <code>init</code> method.
     *
     * <p>
     * Implementations of this interface are responsible for storing the
     * <code>ServletConfig</code> object so that this method can return it. The
     * {@link GenericServlet} class, which implements this interface, already
     * does this.
     *
     * @return the <code>ServletConfig</code> object that initializes this
     *         servlet
     *
     * @see #init
     */
    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.

The status code of the response always should be set for a servlet that
throws or sends an error.

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.
Params:
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
IOException – 
               if an input or output exception occurs/**
     * Called by the servlet container to allow the servlet to respond to a
     * request.
     *
     * <p>
     * This method is only called after the servlet's <code>init()</code> method
     * has completed successfully.
     *
     * <p>
     * The status code of the response always should be set for a servlet that
     * throws or sends an error.
     *
     *
     * <p>
     * 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 <a
     * href
     * ="http://java.sun.com/Series/Tutorial/java/threads/multithreaded.html">
     * the Java tutorial on multi-threaded programming</a>.
     *
     *
     * @param req
     *            the <code>ServletRequest</code> object that contains the
     *            client's request
     *
     * @param res
     *            the <code>ServletResponse</code> object that contains the
     *            servlet's response
     *
     * @exception ServletException
     *                if an exception occurs that interferes with the servlet's
     *                normal operation
     *
     * @exception IOException
     *                if an input or output exception occurs
     */
    public void service(ServletRequest req, ServletResponse res)
            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/**
     * Returns information about the servlet, such as author, version, and
     * copyright.
     *
     * <p>
     * The string that this method returns should be plain text and not markup
     * of any kind (such as HTML, XML, etc.).
     *
     * @return a <code>String</code> containing servlet information
     */
    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.
/**
     * 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 <code>service</code> method have exited or
     * after a timeout period has passed. After the servlet container calls this
     * method, it will not call the <code>service</code> method again on this
     * servlet.
     *
     * <p>
     * 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.
     */
    public void destroy();
}