Servlet入门案例
Posted miantiao312
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了Servlet入门案例相关的知识，希望对你有一定的参考价值。
一、需求：登陆页面，查询数据库是否有此人，并统计登陆的次数、显示成功登陆与否信息
1、登陆页面和登陆成功页面
login.jsp:======================>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>登录页面</h1>
<%
/**
* 判断request域中是否有错误信息：（第一次进入登录页面的时候，没有错误信息）
* * 如果有错误信息：显示错误信息
*/
String msg = "";
if(request.getAttribute("msg") != null){
// 有错误信息：显示错误信息:
msg = (String)request.getAttribute("msg");
}
%>
<h3><font color="red"><%= msg %></font></h3>
<form action="/web_login/LoginServlet" method="post">
<table border="1" width="400">
<tr>
<td>用户名</td>
<td><input type="text" name="username"/></td>
</tr>
<tr>
<td>密码</td>
<td><input type="password" name="password"/></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"/></td>
</tr>
</table>
</form>
</body>
</html>
success.jsp==========================>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>登录成功的页面！</h1>
<%
Integer count = 0;
// 判断，如果ServletContext中有值，获取并显示：
if(this.getServletContext().getAttribute("count")!=null){
count = (Integer)this.getServletContext().getAttribute("count");
}
%>
<h3>登录成功的总人数：<%= count %></h3>
</body>
</html>2、web.xml配置
<servlet>
<description></description>
<display-name>LoginServlet</display-name>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>com.kid.controller.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>
<servlet>
<description></description>
<display-name>InitServlet</display-name>
<servlet-name>InitServlet</servlet-name>
<servlet-class>com.kid.controller.InitServlet</servlet-class>
<!-- 配置启动时加载 -->
<load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>InitServlet</servlet-name>
<url-pattern>/InitServlet</url-pattern>
</servlet-mapping>3、代码逻辑
A、//登陆的Servlet
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
//1、接受页面请求数据
request.setCharacterEncoding("UTF-8");
String username = request.getParameter("username");
String password = request.getParameter("password");
//2、封装数据
User user=new User();
user.setUsername(username);
user.setPassword(password);
//3、查询数据库处理数据
UserModel userModel=new UserModel();
User existUser=userModel.login(user);
//4、判断用户
if(existUser == null) {
request.setAttribute("msg", "用户名或密码错误");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}else {
int count = (Integer) this.getServletContext().getAttribute("count");
count++;
this.getServletContext().setAttribute("count", count);
response.sendRedirect("/web_login/success.jsp");
}
} catch (SQLException e) {
e.printStackTrace();
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
B、//初始化的servlet
public class InitServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* 初始化方法
*/
@Override
public void init() throws ServletException {
int count=0;
this.getServletContext().setAttribute("count", count);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
C、实体类
public class User {
private Integer uid;
private String username;
private String password;
private String nickname;
//getter、setter方法
｝
D、连接数据库查询，并且处理数据
public class UserModel {
/**
* 查询数据库，处理用户的登陆的方法
* @param user
* @return
* @throws SQLException
*/
public User login(User user) throws SQLException {
QueryRunner queryRunner=new QueryRunner(JDBCUtils.getDataSource());
User existUser = queryRunner.query("select * from user where username = ? and password = ?",
new BeanHandler<User>(User.class), user.getUsername(), user.getPassword());
return existUser;
}
}
E、工具类
public class JDBCUtils {
private static final ComboPooledDataSource dataSource = new ComboPooledDataSource();
public static Connection getConnection() throws SQLException{
return dataSource.getConnection();
}
public static DataSource getDataSource(){
return dataSource;
}
}
F、c3p0连接池配置
c3p0-config
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql:///web_login</property>
<property name="user">root</property>
<property name="password">root</property>
<property name="initialPoolSize">5</property>
<property name="minPoolSize">5</property>
<property name="maxPoolSize">20</property>
</default-config>
</c3p0-config>4、登陆成功人数统计分析：
以上是关于Servlet入门案例的主要内容，如果未能解决你的问题，请参考以下文章