[林炳文Evankaka](http://my.csdn.net/Evankaka)原创作品。转载请注明出处[http://blog.csdn.net/evankaka](http://blog.csdn.net/evankaka)
本文要实现Servlet简单登陆验证实例。结构如下
1、LoginCheck.java
~~~
package com.mucfc;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginCheck
*/
@WebServlet("/LoginCheck")
public class LoginCheck extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginCheck() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
//服务器端打印信息
System.out.println("username=" + username);
System.out.println("password=" + password);
if(username!=null&&password!=null && username.equals("linbingwen")&&password.equals("1234")){
//将数据存储在request对象中，传递给下一个servlet使用
request.setAttribute("username", username);
//进行数据的转发
RequestDispatcher dispatcher=request.getRequestDispatcher("Welcome");
dispatcher.forward(request, response);
}
else {
response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,"用户名或密码错误");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
~~~
2、Welcome
~~~
package com.mucfc;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class Welcome
*/
@WebServlet("/Welcome")
public class Welcome extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Welcome() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
//设置编码格式
response.setContentType("text/html;charset=GB18030");
//返回html页面
response.getWriter().println("<html>");
response.getWriter().println("<head>");
response.getWriter().println("<title>登录信息</title>");
response.getWriter().println("</head>");
response.getWriter().println("<body algin=center>");
response.getWriter().println("欢迎【" + username + "】用户登录成功！！！");
response.getWriter().println("</body>");
response.getWriter().println("</html>");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
~~~
3、index.jsp
~~~
<%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>登录</title>
</head>
<body>
<form action="servlet/LoginCheck" method="POST">
用户：<input type="text" name="username" /><br/>
密码：<input type="password" name="password" /><br/>
<input type="submit" value="登录" />
</form>
</body>
</html>
~~~
4、web.xml
~~~
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
<!-- 初始的页面 -->
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<!-- 用户名和密码验证的servlet -->
<servlet>
<servlet-name>LoginCheck</servlet-name>
<servlet-class>com.mucfc.LoginCheck</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginCheck</servlet-name>
<url-pattern>/servlet/LoginCheck</url-pattern>
</servlet-mapping>
<!-- 显示欢迎的servlet -->
<servlet>
<servlet-name>Welcome</servlet-name>
<servlet-class>com.mucfc.Welcome</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Welcome</servlet-name>
<url-pattern>/servlet/Welcome</url-pattern>
</servlet-mapping>
</web-app>
~~~
运行后：
输入正确用户名（lingbingwen)和密码（1234）
输入错误
[
](http://my.csdn.net/Evankaka)
Servlet接口定义三个实现类，分别是FacesServlet， GenericServlet， HttpServlet。下面我们简单的介绍一下。
5、Servlet接口实现类
（1）FacesServlet是一个用于管理利用JSF（JavaServer Faces）构建用户界面的web应用程序请求处理生命周期的Servlet。（FacesServletis a servlet that manages the request processing lifecycle for web applications that are utilizing JavaServer Faces to construct the user interface.），大家如果想深入的学习，可以点这里。
（2）GenericServlet是HttpServlet的父类，包含了servlet的常用方法。GenericServlet使得程序员写servlets更加简单，它提供了初始化和销毁生命周期的方法，以及实现了写日志文件的方法。
（3）HttpServlet指能够处理HTTP请求的servlet。这是开发人员在编写Servlet时，通常应继承这个类即可。
对于这三个实现类，只为大家做一个简单的介绍，如果想深入的研究，直接看API就好。
[
](http://my.csdn.net/Evankaka)
[林炳文Evankaka](http://my.csdn.net/Evankaka)原创作品。转载请注明出处[http://blog.csdn.net/evankaka](http://blog.csdn.net/evankaka)
