/* * 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 * limitations under the License.
*/ package jakarta.servlet;
import java.io.IOException;
/** * 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
*/ publicinterface Servlet {
/** * 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
*/ void init(ServletConfig config) throws ServletException;
/** * 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
*/
ServletConfig getServletConfig();
/** * 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
*/ void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;
/** * 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
*/
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 <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.
*/ void destroy();
}
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