本文介绍了使用Java Servlet创建一个简单的登录项目的两种方法。一种是通过传统web.xml配置，另一种是利用web3.0的注解配置。每种方法都详细展示了配置过程及核心代码。
学学Java Servlet：创建一个简单的Servlet
项目介绍：
创建一个简单的WebProject项目，通过项目配置，用两种配置方法实现servlet一个简单的登录登出小项目。
登录成功显示成功，登录失败显示失败。so easy...
配置简介：myeclipse，tomcat7.0
详细步骤：
1、创建一个web project项目，创建的时候选择J2EE6.0的版本
项目结构图：
然后下一步、结束就好。接着写三个页面，登录、成功、失败页面。（注意编码）
login.jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'login.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="<%=basePath%>login" method="post">
用户:<input type="text" name="name"/><br>
密码:<input type="password" name="passwd"/><br>
<input type="submit" value="提交">
</form>
</body>
</html>
success.jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'success.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
登录成功！
</body>
</html>
fail.jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'fail.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
帐号或密码错误，登录失败！<br>
<a href="<%=basePath%>">返回登录</a>
</body>
</html>
注：根据web的版本可以不同的实现servlet的访问，现在3.0版本的居多，也少了更多的配置信息，用注解显得更加的方便灵活。web.xml版本在Myeclipse里面可以很直接的看到：
还有就是通过具体的配置文件信息，也明确的写明了web2.5和web3.0的版本信息：
web.xml2.5配置信息：
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
</web-app>web.xml3.0配置信息
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
</web-app>版本的选择也能让我们用不同的方式来开发Servlet，下面我们就用两种方法来写这个Demo。
方法一：web3.0以下版本的传统web.xml配置
1、web.xml的配置：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<!-- 加载的默认首页 -->
<welcome-file-list>
<welcome-file>/WEB-INF/page/login.jsp</welcome-file>
</welcome-file-list>
<!-- 配置Servlet -->
<servlet>
<!-- Servlet名：在配置文件中唯一 -->
<servlet-name>LoginServlet</servlet-name>
<!-- Servlet对应的类 -->
<servlet-class>com.frend.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<!-- Servlet名对应前面 -->
<servlet-name>LoginServlet</servlet-name>
<!-- /login：请求的url -->
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
2、Servlet类：
package com.frend;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 5798229038714266939L;
@Override
public void init() throws ServletException {
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("utf-8");//设置编码格式以支持中文
String name = request.getParameter("name");//获取账户名
String passwd = request.getParameter("passwd");//获取密码
System.out.println("*****账户："+name+",密码："+passwd);//打印账户密码
RequestDispatcher dispatcher = null;
//验证账户名和密码
if(!"frend".equals(name) || !"abc123".equals(passwd)){
dispatcher = request.getRequestDispatcher("/WEB-INF/page/fail.jsp");//获取RequestDispatcher对象
}else{
dispatcher = request.getRequestDispatcher("/WEB-INF/page/success.jsp");//获取RequestDispatcher对象
}
dispatcher.forward(request, response);//向目的路径跳转
}
@Override
public void destroy() {
}
}
方法二：web3.0以上版本的注解配置
1、web.xml的配置：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<!-- 加载的默认首页 -->
<welcome-file-list>
<welcome-file>/WEB-INF/page/login.jsp</welcome-file>
</welcome-file-list>
</web-app>2、Servlet类：
/**
* @(#) LoginServlet.java 2016-7-20 上午10:29:48
*
* Copyright (c) 2014-2015 Diyvc, Inc.
* 103 Sports Road, Victoria Plaza tower 1104, Tianhe District Guangzhou City, China.
* All rights reserved.
*
*/
package com.frend;
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;
@WebServlet(name="LoginServlet",urlPatterns="/login")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 5798229038714266939L;
@Override
public void init() throws ServletException {
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("utf-8");//设置编码格式以支持中文
String name = request.getParameter("name");//获取账户名
String passwd = request.getParameter("passwd");//获取密码
System.out.println("*****账户："+name+",密码："+passwd);//打印账户密码
RequestDispatcher dispatcher = null;
//验证账户名和密码
if(!"frend".equals(name) || !"abc123".equals(passwd)){
dispatcher = request.getRequestDispatcher("/WEB-INF/page/fail.jsp");//获取RequestDispatcher对象
}else{
dispatcher = request.getRequestDispatcher("/WEB-INF/page/success.jsp");//获取RequestDispatcher对象
}
dispatcher.forward(request, response);//向目的路径跳转
}
@Override
public void destroy() {
}
}
页面截图：
1、失败情景
2、成功情景
小结：
传统的web.xml适合配置文件控制，但是servlet多的情况下完全不方便管理；
注解方式简单方便，很适用开发。
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