登陆案例
1. 需求
- 编写 login.html 登陆页面
- 使用 Druid 数据库连接池技术，操作 MySQL 中建立的 user 表
- 使用 JDBCTemplate 技术封装 JDBC
- 登陆成功跳转到 SuccessServlet 展示：登陆成功，欢迎您！
- 登陆失败跳转到 FailServlet 展示：登陆失败，用户名或密码错误！
2. 实现步骤
注意一下开发环境，我这里的开发环境是：IDEA_2019.2.3 、MySQL_8.0.17 和 Tomcat_9.0.26
关于这个demo，我已经上传到CSDN资源下载，可以直接下载看。
2.1 创建数据库和表
-- 创建数据库
CREATE DATABASE IF NOT EXISTS example CHARACTER SET utf8 ;
USE example;
-- 创建表
CREATE TABLE USER(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(32) UNIQUE NOT NULL,
password VARCHAR(32) NOT NULL
);
-- 添加数据
INSERT INTO USER VALUES(1,"admin","123");
2.2 登陆页面（login.html）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/loginTest/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>
注意：
- action属性值为：/虚拟路径/资源路径
2.3 数据库连接池配置文件（druid.properties）
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/example?serverTimezone=UTC
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000
2.4 Java 代码部分
2.4.1 导入Jar包（web/WEB-INFO/lib）
Jar包 需要放在 WEB-INFO/lib 路径下，包括以下：
- spring-tx-5.0.0.RELEASE.jar
- spring-jdbc-5.0.0.RELEASE.jar
- spring-core-5.0.0.RELEASE.jar
- spring-beans-5.0.0.RELEASE.jar
- mysql-connector-java-8.0.17.jar
- mchange-commons-java-0.2.12.jar
- druid-1.0.9.jar
- commons-logging-1.2.jar
- commons-beanutils-1.8.0.jar
2.4.2 User 实体类（src/com.login.domain）
package com.login.domain;
public class User {
private Integer id;
private String username;
private String password;
public Integer getId() {
return id;
}
public void setId(Integer 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;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
2.4.3 编写 JdbcTemplate 的工具类（src/com.login.utils）
package com.login.utils;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
/**
* JDBC工具类，使用Durid连接池
*/
public class JDBCUtils {
private static DataSource ds;
static {
try {
//加载配置文件
Properties pro = new Properties();
//使用ClassLoader加载配置文件，获取字节输入流
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
pro.load(is);
//初始化连接池对象
ds = DruidDataSourceFactory.createDataSource(pro);
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
//获取连接池对象
public static DataSource getDataSource() {
return ds;
}
//获取Connection对象
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
}
2.4.4 UserDao 类（src/com.login.dao）
package com.login.dao;
import com.login.domain.User;
import com.login.utils.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
/**
* 提供 login 的方法，操作数据库中 User表
*/
public class UserDao {
//声明JDBCTemplate对象共用
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
/**
* 登陆方法
* @param loginUser 只有用户名和密码
* @return user 包含用户的全部数据,没有查询到，返回null值
*/
public User login(User loginUser){
try {
// 1. 编写sql
String sql = "select * from user where username = ? and password = ?";
// 2. 调用query方法
User user = template.queryForObject(sql,
new BeanPropertyRowMapper<User>(User.class),
loginUser.getUsername(),
loginUser.getPassword());
return user;
}catch (DataAccessException e) {
e.printStackTrace();
return null;
}
}
}
2.4.4 编写服务类 (src/com.login.web.servlet)
2.4.4.1 登陆服务函数（LoginServlet）
package com.login.web.servlet;
import com.login.dao.UserDao;
import com.login.domain.User;
import org.apache.commons.beanutils.BeanUtils;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1. 设置编码
req.setCharacterEncoding("utf-8");
// 2. 获取所有请求参数
Map<String,String[]> map = req.getParameterMap();
// 3. 创建User对象
User loginUser = new User();
// 3.2 使用BeanUtils封装
try{
BeanUtils.populate(loginUser,map);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
//4. 调用 UserDao 的 Login 方法
UserDao dao = new UserDao();
User user = dao.login(loginUser);
//5. 判断user
if (user == null){//登陆失败
req.getRequestDispatcher("/failServlet").forward(req,resp);
}else {//登陆成功，存储数据。
//存储数据
req.setAttribute("user",user);
//转发
req.getRequestDispatcher("/successServlet").forward(req,resp);
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}
2.4.4.2 登陆成功服务函数（SuccessServlet）
package com.login.web.servlet;
import com.login.domain.User;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取 request域中共享的 user对象
User user = (User) request.getAttribute("user");
if (user != null) {
//设置编码
response.setContentType("text/html;charset=utf-8");
//给页面输出一句话
response.getWriter().write("登陆成功! " + user.getUsername() + "欢迎您！");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
2.4.4.3 登陆失败服务函数（FailServlet）
package com.login.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//给页面写一句话
//设置编码
response.setContentType("text/html;charset=utf-8");
//输出
response.getWriter().write("登陆失败，用户名或密码错误！");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
时间：2019年11月2日00:01:08
