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标题: 学习感悟 [打印本页]

作者: qq531988106 时间: 2019-9-26 13:39
标题: 学习感悟
用户登录案例：
* 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，day14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

* 开发步骤
1. 创建项目，导入html页面，配置文件，jar包
2. 创建数据库环境
CREATE DATABASE day14;
USE day14;
CREATE TABLE USER(

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

3. 创建包cn.itcast.domain,创建类User
package cn.itcast.domain;
/**
   * 用户的实体类
   */
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 + '\'' +
                  '}';
      }
}
4. 创建包cn.itcast.util,编写工具类JDBCUtils
package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import javax.xml.crypto.Data;
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 {
            //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) {
            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. 创建包cn.itcast.dao,创建类UserDao,提供login方法

package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.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表的类
   */
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包含用户全部数据,没有查询到，返回null
      */
      public User login(User loginUser){
         try {
            //1.编写sql
            String sql = "select * from user where username = ? and password = ?";
            //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();//记录日志
            return null;
         }
      }
}

6. 编写cn.itcast.web.servlet.LoginServlet类
package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.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);

         //5.判断user
         if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
         }else{
            //登录成功
            //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);
      }
}

7. 编写FailServlet和SuccessServlet类
@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){
            //给页面写一句话

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

      }

@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("登录失败，用户名或密码错误");

      }

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

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