实例1：
1.新建webproject2项目 对servlet进行申明，设置映射路径 2.新建LoginFormServlet.java
Code package com.jh.webproject2;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginFormServlet extends HttpServlet { /** * Constructor of the object. */ public LoginFormServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); out.println("<form method=\"POST\" action=\"/webproject2/servlet/LoginForm\">");//"+request.getContextPath()+"可替代/webproject2 out.println("用户名：<input type='text' name='username'><br>"); out.println("密码：<input type='password' name='password'><br>"); out.println("<input type='submit' value='提交'>"); out.println("<input type='reset' value='重置'>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); request.setCharacterEncoding("utf-8"); out.println("用户名:"+request.getParameter("username")+"<br>"); out.println("密码:"+request.getParameter("password")+"<br>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } } 实例2：(在实例1的基础上的改进)
1.新建html文件 2.新建LoginServlet.java 重写doPost方法，不需要doGet方法
Code package com.jh.webproject2;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServlet extends HttpServlet { /** * Constructor of the object. */ public LoginServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out .println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); request.setCharacterEncoding("utf-8"); out.println("用户名："+request.getParameter("username")+"<br>"); out.println("密码:"+request.getParameter("password")+"<br>"); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } } 3. 修改路径
实例3：网络调查表
1.新建survey.htm 2.新建SurveyServlet.java 使用doGet,doPost方法，实际上主要处理的是doPost请求
Code package com.jh.webproject2;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class SurveyServlet extends HttpServlet { /** * Constructor of the object. */ public SurveyServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); request.setCharacterEncoding("utf-8"); out.println("姓名："+filterHtml(request.getParameter("name"))+"<br>"); out.println("Email："+filterHtml(request.getParameter("email"))+"<br>"); out.println("年龄："+request.getParameter("age")+"岁"+"<br>"); out.println("编程时间："+request.getParameter("codetime")+"个月"+"<br>"); out.println("操纵系统："); String os[]=request.getParameterValues("os"); //枚举输出 out.println("<ul>"); for(int i=0;i<os.length;i++) { out.println("<li>"+os[i]+"</li>"); } out.println("</ul><br>"); out.println("编程语言："); String language[]=request.getParameterValues("language"); //枚举输出 out.println("<ul>"); for(int i=0;i<language.length;i++) { out.println("<li>"+language[i]+"</li>"); } out.println("</ul><br>"); out.println("建议:"+filterHtml(request.getParameter("comment"))+"<br>"); out.println("</BODY>"); out.println("</HTML>"); out.flush(); out.close(); } //进行过滤 public String filterHtml(String value){ value=value.replaceAll("&", "&"); value=value.replaceAll("<", "<");//注：替换script代码，只须把代码中的"<"或">"号替换成普通文本输出就可以 value=value.replaceAll(">", ">"); value=value.replaceAll("", " "); value=value.replaceAll("'", "'"); value=value.replaceAll("\"", """);//这地方是替换双引号，"\"是对双引号进行转译 value=value.replaceAll("\n", "<br>"); return value; } public void init() throws ServletException { // Put your code here } } 3.对输入的东西进行过滤
使用filterHtml方法（具体实现方法在上面所列代码中）************************************************
也是在本例中，学到一个小东西，是在每次上传文件时要用的东西一个浏览框：
<input type="file" value="浏览"/>很简单很实用吧。实例4：在不知道所有参数的情况下，获取参数的名字以及参数所对应的值
1.新建survey2.htm 2.新建SurveyServlet2.java
Code //在不知道所有参数的情况下，获取参数的名字以及参数所对应的值package com.jh.webproject2;import java.io.IOException;import java.io.PrintWriter;import java.util.Enumeration;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class SurveyServlet2 extends HttpServlet { /** * */ private static final long serialVersionUID = 7799557625643493959L; /** * Constructor of the object. */ public SurveyServlet2() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); request.setCharacterEncoding("utf-8"); Enumeration e=request.getParameterNames(); String parameterName=null; while(e.hasMoreElements()){ //枚举输出 parameterName=(String)e.nextElement(); String values[]=request.getParameterValues(parameterName);//得到每一个参数的值，通过下面的for循环输出 out.println(parameterName+"<br>"); out.println("<ul>"); for(int i=0;i<values.length;i++) { out.println("<li>"+values[i]+"</li>"); } out.println("</ul><br>"); } out.println("</BODY>"); out.println("</HTML>"); out.flush(); out.close(); } public String filterHtml(String value){ value=value.replaceAll("&", "&"); value=value.replaceAll("<", "<");//注：替换script代码，只须把代码中的"<"或">"号替换成普通文本输出就可以 value=value.replaceAll(">", ">"); value=value.replaceAll("", " "); value=value.replaceAll("'", "'"); value=value.replaceAll("\"", """);//这地方是替换双引号，"\"是对双引号进行转译 value=value.replaceAll("\n", "<br>"); return value; } }