1，下载源码，点击此处可下载
2，创建web项目
我这里以jdbc这个web项目为例讲解
在javaee libraries中有个javaee.jar包，选中它-->右击--》Properties
找到你下载的jar包
打开---apply 即可】
在任意一个.java文件中，编写servlet，按住ctrl键，鼠标单击类（或接口）名，即可查看源码
下面是servlet完整源码
/** DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.** Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.** The contents of this file are subject to the terms of either the GNU* General Public License Version 2 only ("GPL") or the Common Development* and Distribution License("CDDL") (collectively, the "License"). You* may not use this file except in compliance with the License. You can* obtain a copy of the License at* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html* or packager/legal/LICENSE.txt. See the License for the specific* language governing permissions and limitations under the License.** When distributing the software, include this License Header Notice in each* file and include the License file at packager/legal/LICENSE.txt.** GPL Classpath Exception:* Oracle designates this particular file as subject to the "Classpath"* exception as provided by Oracle in the GPL Version 2 section of the License* file that accompanied this code.** Modifications:* If applicable, add the following below the License Header, with the fields* enclosed by brackets [] replaced by your own identifying information:* "Portions Copyright [year] [name of copyright owner]"** Contributor(s):* If you wish your version of this file to be governed by only the CDDL or* only the GPL Version 2, indicate your decision by adding "[Contributor]* elects to include this software in this distribution under the [CDDL or GPL* Version 2] license." If you don't indicate a single choice of license, a* recipient has the option to distribute your version of this file under* either the CDDL, the GPL Version 2 or to extend the choice of license to* its licensees as provided above. However, if you add GPL Version 2 code* and therefore, elected the GPL Version 2 license, then the option applies* only if the new code is made subject to such option by the copyright* holder.*** This file incorporates work covered by the following copyright and* permission notice:** Copyright 2004 The Apache Software Foundation** Licensed 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 javax.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>javax.servlet.GenericServlet</code> or an HTTP servlet that* extends <code>javax.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.** @author Various** @see GenericServlet* @see javax.servlet.http.HttpServlet**/public interface 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**/public 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**/public 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**/public 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**/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* <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(); }
