数据库准备：
CREATE DATABASE web;
USE web;
CREATE TABLE users(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(64),
PASSWORD VARCHAR(64),
email VARCHAR(64)
);
INSERT INTO users (username,PASSWORD,email)
VALUES("tom","123","tom@qq.com"),("lucy","123","lucy@qq.com");
对应User类：
package domain;
public class User {
private int id;
private String username;
private String password;
private String email;
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", password=" + password + ", email=" + email + "]";
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
前端页面:
login.html:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/WEB2/login" method="post">
用户名：<input type="text" name="username"><br/>
密码：<input type="password" name="password"><br/>
<input type="submit" value="登录" > </form>
</body>
</html>
Servlet:
用到c3p0连接池，dbutils工具类，mysql驱动，注意导入相关包
utils包：
自定义连接池工具类：
package 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 DataSourceUtils { private static DataSource dataSource = new ComboPooledDataSource(); private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>(); // 直接可以获取一个连接池
public static DataSource getDataSource() {
return dataSource;
} // 获取连接对象
public static Connection getConnection() throws SQLException { Connection con = tl.get();
if (con == null) {
con = dataSource.getConnection();
tl.set(con);
}
return con;
} // 开启事务
public static void startTransaction() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.setAutoCommit(false);
}
} // 事务回滚
public static void rollback() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.rollback();
}
} // 提交并且 关闭资源及从ThreadLocall中释放
public static void commitAndRelease() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.commit(); // 事务提交
con.close();// 关闭资源
tl.remove();// 从线程绑定中移除
}
} // 关闭资源方法
public static void closeConnection() throws SQLException {
Connection con = getConnection();
if (con != null) {
con.close();
}
} public static void closeStatement(Statement st) throws SQLException {
if (st != null) {
st.close();
}
} public static void closeResultSet(ResultSet rs) throws SQLException {
if (rs != null) {
rs.close();
}
} }
c3p0-config.xml配置文件：
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="user">root</property>
<property name="password">xuyiqing</property>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql:///web</property>
</default-config>
</c3p0-config>
核心类：
package login; import java.io.IOException;
import java.sql.SQLException; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler; import domain.User;
import utils.DataSourceUtils; public class LoginServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//1.获取用户名密码
String username = request.getParameter("username");
String password = request.getParameter("password");
//2.数据库中验证
QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from users where username=? and password=?";
User user = null;
try {
user = runner.query(sql,new BeanHandler<User>(User.class) ,username,password);
} catch (SQLException e) {
e.printStackTrace();
}
if(user!=null){
//登录成功
response.getWriter().write(user.toString());
}else {
//登录失败
response.getWriter().write("Sorry!Your username or password is wrong."); }
} protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
web.xml配置：
<?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" id="WebApp_ID" version="2.5">
<display-name>WEB2</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<description></description>
<display-name>LoginServlet</display-name>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>login.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
完成！
访问http://localhost:8080/WEB2/login.html
输入正确的用户名和密码点击登录
结果如下：
完成！
成功！
接下来，提升功能：
统计成功登录的人数：
package login; import java.io.IOException;
import java.sql.SQLException; import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler; import domain.User;
import utils.DataSourceUtils; public class LoginServlet extends HttpServlet { @Override
public void init() throws ServletException {
int count = 0;
// 域对象
this.getServletContext().setAttribute("count", count);
} protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 1.获取用户名密码
String username = request.getParameter("username");
String password = request.getParameter("password");
// 2.数据库中验证
QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from users where username=? and password=?";
User user = null;
try {
user = runner.query(sql, new BeanHandler<User>(User.class), username, password);
} catch (SQLException e) {
e.printStackTrace();
}
if (user != null) {
// 登录成功
// 利用域对象的方法
ServletContext context = this.getServletContext();
Integer count = (Integer) context.getAttribute("count");
count++;
response.getWriter().write(user.toString() + "You are the " + count + " person to log in successfully");
context.setAttribute("count", count);
} else {
// 登录失败
response.getWriter().write("Sorry!Your username or password is wrong."); }
} protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}