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1.登录案例的servlet层代码 package cn.itcast.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import cn.itcast.dao.UserDao; import cn.itcast.dao.impl.UserDaoImpl; import cn.itcast.domain.User; public class LoginServlet extends HttpServlet { private UserService userService = new UserServicempl(); public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //解决Post参数乱码 request.setCharacterEncoding("UTF-8"); //1.获得参数(用户名,密码) String name =request.getParameter("name"); String password =request.getParameter("password"); //非空校验 //2.根据用户名查询数据库,获得User对象 User u = userService .getByName(name); if(u==null){ // 查询不到=>用户名不存在=>转发到登录页面提示用户名不存在 request.setAttribute("error", "用户名不存在!"); request.getRequestDispatcher("/login.jsp").forward(request, response); return; } //查询到了=>继续执行 //3.比对用户填写的密码与数据库中正确的密码 if(!u.getPassword().equals(password)){ // //比对不一致=>密码错误=>转发到登录页面提示密码错误 request.setAttribute("error", "密码错误!"); request.getRequestDispatcher("/login.jsp").forward(request, response); return; } //比对一致=>继续执行 //直接跳转到首页页面 } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } 2.登录案例的service层代码package cn.itcast.service; import cn.itcast.dao.UserDao; import cn.itcast.dao.impl.UserDaoImpl3; import cn.itcast.domain.User; public class UserService { UserDao userDao = new UserDaoImpl(); public User getByName(String name){ return userDao.getByName(name); } } 3.登录案例的dao层代码package cn.itcast.dao.impl; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import cn.itcast.dao.UserDao; import cn.itcast.domain.User; import cn.itcast.utils.DBUtils; public class UserDaoImpl implements UserDao { public User getByName(String name) { User u = null; //1 获得连接 Connection conn = JDBCUtils .getConnection(); //2 准备sql String sql ="select * from t_user where name = ?"; //3 创建PreparedStatement对象 PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(sql); //4 设置参数 ps.setString(1, name); //5 执行sql rs = ps.executeQuery(); //6 封装并返回结果 if(rs.next()){ u = new User(); u.setId(rs.getInt("id")); u.setName(rs.getString("name")); u.setPassword(rs.getString("password")); u.setEmail(rs.getString("email")); } } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException("根据名称获得用户,执行sql异常"); }finally{ //关闭资源 DBUtils.close(rs, ps, conn); } return u; } } 4.连接数据库的工具类package cn.itcast.utils; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import javax.sql.DataSource; import com.mchange.v2.c3p0.ComboPooledDataSource; public class JDBCUtils { private static final ComboPooledDataSource DATA_SOURCE =new ComboPooledDataSource(); /** * 获得连接的方法 */ public static Connection getConnection(){ Connection conn = null; try { conn = DATA_SOURCE.getConnection(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return conn; } public static DataSource getDataSource(){ return DATA_SOURCE; } } 5.连接数据库的配置文件内容<?xml version="1.0" encoding="UTF-8"?> <c3p0-config> <default-config> <property name="driverClass">com.mysql.jdbc.Driver</property> <property name="jdbcUrl">jdbc:mysql:///day09</property> <property name="user">root</property> <property name="password">123</property> <property name="initialPoolSize">5</property> <property name="maxPoolSize">20</property> </default-config> </c3p0-config> 注意：此文件名称必须是c3p0-config.xml因为当我new ComboPooledDataSource();此类会默认从项目的src下去查找名称是c3p0-config.xml文件，当然也可以不是这个名称，但是此时new ComboPooledDataSource();new对象的时候就要在构造方法里面去填写你指定的文件名称以及路径。 6.登录案例的页面代码<%@ 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 'index.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> <h1>用户登录</h1> <form action="${pageContext.request.contextPath}/LoginServlet" method="post" > <table border="1" > <tr> <td>用户名:</td> <td><input type="text" name="name" value="${param.name}" /><font color="red" >${errorMap.name}</font></td> </tr> <tr> <td>密码:</td> <td><input type="password" name="password" value="" /><font color="red" >${errorMap.password}</font></td> </tr> <tr> <td colspan="2" align="center" ><input type="submit" name="" value="登录" /></td> </tr> </table> <font color="red" >${error}</font> </form> </body> </html> 注意：页面的input框(除提交按钮的input框不需要写name)中必须填有name属性和值，因为表单提交提交的内容是name属性值，此时后台通过request.getParameter("name");就可以直接得到用户输入的值 7.登录案例的web.xml配置代码<?xml version="1.0" encoding="UTF-8"?> <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 <display-name></display-name> <servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>cn.itcast.servlet.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app> | 
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