JavaWeb入门案例--模拟登录

小小孙十八
103 阅读3分钟

本项目需求

  1. 编写login.html登录页面，包含username & password 两个输入框
  2. 使用Druid数据库连接池技术,操作mysql，ittest数据库中user表
  3. 使用JdbcTemplate技术封装JDBC
  4. 登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您
  5. 登录失败跳转到FailServlet展示：登录失败，用户名或密码错误

准备工作

首先导入jar包

image.png

编写一个druid.properties配置文件

driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/ittest
username=root
password=123456
initialSize=5
maxActive=10
maxWait=3000

准备数据库

-- user表
create table user(
    id int primary key auto_increment,
    username varchar(32),
    password varchar(32)
)

insert into user values(null,'zhangsan','123');
insert into user values(null,'lisi','234');

开始编程

编写一个简单的登陆页面，login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录</title>
</head>
<body>
<!-- login.html中form表单的action路径的写法：虚拟目录+Servlet的资源路径-->
    <form action="/day_userLogin/loginServlet" 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>

image.png

给数据库创建实体类User.java

package com.sun.domain;

//创建用户的实体类（javabean）
public class User {
    private int id;
    private String username;
    private String password;

    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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + ''' +
                ", password='" + password + ''' +
                '}';
    }
}

创建数据库连接工具包JDBCUtils.java

package com.sun.util;

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Druid连接池
public class JDBCUtils {
//工具类的方法建议为静态
    private static DataSource ds;

    static {
        try {
            //1、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);

            //2、初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    //获取连接池对象
    public static DataSource getDataSource(){
        return ds;
    }

    //获取链接Connection对象
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

操作数据库中user表，UserDao.java

package com.sun.dao;

import com.sun.domain.User;
import com.sun.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

//操作数据库中User表中的类
//提供login的方法，来完成数据库的操作
public class UserDao {

    //声明JDBCTemplate对象公用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 登录方法
     * @param loginUser  只有用户名和密码
     * @return   user包含用户全部数据。没查询到返回null
     */
    public User login(User loginUser){
        try {
            //1、编写SQL
            String sql = "select * from user where username = ? and password = ?";
            //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();//日志
            return null;
        }
    }
}

自己可以测试数据库代码是否健全，UserDaoTest.java

package com.sun.test;

import com.sun.dao.UserDao;
import com.sun.domain.User;
import org.testng.annotations.Test;

public class UserDaoTest {

    @Test
    public void testLogin(){
        User loginuser = new User();
        loginuser.setUsername("zhangsan");
        loginuser.setPassword("123");

        UserDao dao = new UserDao();
        User user = dao.login(loginuser);

        System.out.println(user);

    }
}
编写LoginServlet.java来实现基本的登录逻辑

注意，此处的代码有些不方便，在下一篇文章会结合BeanUtils工具类进行改善。 链接：BeanUtils的基本使用 - 掘金 (juejin.cn)

package com.sun.web.servlet;

import com.sun.dao.UserDao;
import com.sun.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("/loginServlet")
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、获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3、封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);
        //4、调用userDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);
        //判断user
        if (user == null){
            //登录失败，跳转到failServlet
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        } else {
            //登录成功，跳转successServlet
            //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);
    }
}

登录失败跳转页面failServlet.java

package com.sun.web.servlet;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "failServlet", value = "/failServlet")
public class failServlet extends HttpServlet {
    @Override
    protected void doGet(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("登录失败，用户名或密码错误");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

image.png

登陆成功跳转页面successServlet.java

package com.sun.web.servlet;

import com.sun.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(name = "successServlet", value = "/successServlet")
public class successServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User) request.getAttribute("user");
        //给页面写一句话

        if (user != null){
            //设置编码
            response.setContentType("text/html;charset=utf-8");
            //输出
            response.getWriter().write("登录成功！"+user.getUsername()+"，欢迎您");
        }
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
}

image.png

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