Java 之 request 案例——用户登录

用户登录案例需求：

1.编写login.html登录页面	username & password 两个输入框
2.使用Druid数据库连接池技术,操作mysql，db1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

　　

分析示意图：

开发步骤：

1、创建 JavaEE项目，创建 login.html 页面，创建durid.properties配置文件，导入 jar包

2、创建数据库环境

 CREATE DATABASE db1;
 USE db1;
 CREATE TABLE USER(

   id INT PRIMARY KEY AUTO_INCREMENT,
   username VARCHAR(32) UNIQUE NOT NULL,
   PASSWORD VARCHAR(32) NOT NULL
);

3、创建 JavaBean，User类

 /*
 javaBean 类
  */
 public class User {

     private int id;
     private String username;
     private String password;

     public User() {
     }

     public User(int id, String username, String password) {
         this.id = id;
         this.username = username;
         this.password = password;
     }

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

4、创建数据库连接池工具类 JDBCUtils

 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;

 public class JDBCUtils {

     private static DataSource ds;

     static {
         try {
             // 加载配置文件
             Properties prop = new Properties();

             //使用classloader 加载配置文件进内存
             InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");

             prop.load(is);

             // 初始化连接池对象
             ds = DruidDataSourceFactory.createDataSource(prop);
         } catch (IOException e) {
             e.printStackTrace();
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

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

     /*
         获取连接connection对象
      */
     public static Connection getConnection() throws SQLException {
         return ds.getConnection();
     }
 }

5、创建 UserDao类，提供 login 方法

 import org.springframework.dao.DataAccessException;
 import org.springframework.jdbc.core.BeanPropertyRowMapper;
 import org.springframework.jdbc.core.JdbcTemplate;

 public class UserDao {
     //声明 JDBCTemplate 对象共用
     private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

     /**
      * 登录方法
      * @param loginUser 只有用户名和密码
      * @return user 包含用户的全部数据没有查询到返回 null
      */
    public User login(User loginUser) {

        try {
            // 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();
            return null;
        }

    }
 }

6、测试 login 方法

 import org.junit.Test;

 public class LoginTest {

     @Test
     public void test() {
         User loginuser = new User();
         loginuser.setUsername("admin");
         loginuser.setPassword("admin");
         UserDao dao = new UserDao();

         User user = dao.login(loginuser);
         System.out.println(user);

     }
 }

7、编写  loginServlet 类

 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("/loginservlet")
 public class LoginServlet extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // 1.设置编码
         request.setCharacterEncoding("utf-8");

        // 2 获取请求参数
          String username = request.getParameter("username");
         String password = request.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);

         //5. 判断
         if(user == null) {
             request.getRequestDispatcher("/failServlet").forward(request,response);
         } else {
             request.setAttribute("user",user);
             request.getRequestDispatcher("/successServlet").forward(request,response);
         }
     }

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

8、编写 FailServlet 类和 SuccessServlet 类

　　FailServlet 类

 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 {
         response.setContentType("text/html;charset=utf-8");

         response.getWriter().write("登录失败");
     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

     }
 }

　　SuccessServlet 类

 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 {
         User user = (User) request.getAttribute("user");

         if(user!=null) {
             // 设置编码
             request.setCharacterEncoding("utf-8");
             response.setContentType("text/html;charset=utf-8");

             response.getWriter().write("登录成功"+user.getUsername()+"欢迎您");
         }
     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

     }
 }

9、login.html中form表单的action路径的写法

action="虚拟目录+Servlet的资源路径"