java入门作业-DAO，读取sql数据库

阿里云国内75折 回扣 微信号：monov8
阿里云国际，腾讯云国际，低至75折。AWS 93折 免费开户实名账号 代冲值 优惠多多 微信号：monov8 飞机：@monov6

DAO意思是数据库、访问、对象。有了前后端思想。

需要下载mysql并下载链接自己设置好密码。可以在navicat等软件链接打开。

材料是jc0122.sql里面的admin_info是要操作的表。不像上一节需要把数据库文件放到java目录里。数据库只要在本地即可。

 一、简单测试链接读取

要读取admin_info所有的数据弄一个对象。保证后续输出。

 AdminInfo

package S4.pojo;

import java.util.Date;

public class AdminInfo {
    private Integer adminId;
    private String adminName;
    private String adminPwd;
    private Integer roleId;
    private Integer adminState;
    private Date adminCtime;
    private Date adminMtime;

    public AdminInfo() {
    }

    public AdminInfo(Integer adminId, String adminName, String adminPwd, Integer roleId, Integer adminState, Date adminCtime, Date adminMtime) {
        this.adminId = adminId;
        this.adminName = adminName;
        this.adminPwd = adminPwd;
        this.roleId = roleId;
        this.adminState = adminState;
        this.adminCtime = adminCtime;
        this.adminMtime = adminMtime;
    }

    public Integer getAdminId() {
        return adminId;
    }

    public void setAdminId(Integer adminId) {
        this.adminId = adminId;
    }

    public String getAdminName() {
        return adminName;
    }

    public void setAdminName(String adminName) {
        this.adminName = adminName;
    }

    public String getAdminPwd() {
        return adminPwd;
    }

    public void setAdminPwd(String adminPwd) {
        this.adminPwd = adminPwd;
    }

    public Integer getRoleId() {
        return roleId;
    }

    public void setRoleId(Integer roleId) {
        this.roleId = roleId;
    }

    public Integer getAdminState() {
        return adminState;
    }

    public void setAdminState(Integer adminState) {
        this.adminState = adminState;
    }

    public Date getAdminCtime() {
        return adminCtime;
    }

    public void setAdminCtime(Date adminCtime) {
        this.adminCtime = adminCtime;
    }

    public Date getAdminMtime() {
        return adminMtime;
    }

    public void setAdminMtime(Date adminMtime) {
        this.adminMtime = adminMtime;
    }

    @Override
    public String toString() {
        return "AdminInfo{" +
                "adminId=" + adminId +
                ", adminName='" + adminName + '\'' +
                ", adminPwd='" + adminPwd + '\'' +
                ", roleId=" + roleId +
                ", adminState=" + adminState +
                ", adminCtime=" + adminCtime +
                ", adminMtime=" + adminMtime +
                '}';
    }
}

Test注意localhost、pwd密码密码是自己修改的。uri后面的jc0122是.sql文件可能有许多表格。

package S4.test;

import S4.pojo.AdminInfo;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {

        try {
            Class.forName("com.mysql.jdbc.Driver");// jdbc驱动
            String uri = "jdbc:mysql://localhost:3306/jc0122?useUnicode=ture&serverTimezone=UTC";
            String userid = "root";
            String pwd = "123456";
            Connection connection = DriverManager.getConnection(uri,userid,pwd);

            System.out.println("connection:"+connection);

            //开始查询
            String sql = "select * from admin_info ";

            PreparedStatement ps = connection.prepareStatement(sql);
            ResultSet set = ps.executeQuery();

            List<AdminInfo> list = new ArrayList<>();
            while (set.next()){

                AdminInfo adminInfo = new AdminInfo();
                //匹配java对象的属性和数据库对象的字段一一对应起来
                adminInfo.setAdminId(set.getInt("admin_id"));
                adminInfo.setAdminName(set.getString("admin_name"));
                adminInfo.setAdminPwd(set.getString("admin_pwd"));
                adminInfo.setAdminCtime(set.getDate("admin_ctime"));
                adminInfo.setAdminMtime(set.getDate("admin_mtime"));
                adminInfo.setAdminState(set.getInt("admin_state"));
                adminInfo.setRoleId(set.getInt("role_id"));

                System.out.println(adminInfo);
                list.add(adminInfo);


            }


            //后面就是展示到UI上面去



        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }


    }
}

如果链接成功会提示connection并根据需求读出数据。

 二、根据id、名字读取所有数据分页查询

 AdminInfo还是上面那个

创建Interface类AdminDao。按要求声明一下。

package S4.dao;

import S4.pojo.AdminInfo;

import java.util.List;

public interface AdminDao {

    /**
     * 通过账号密码查询admin对象
     * @param name 账号
     * @param pwd 密码
     * @return  admin对象
     */
    AdminInfo selectByNameAndPwd(String name,String pwd);

    /**
     * 分页查询用户
     * @param start 起始数
     * @param limit 条数
     * @return admin对象集合
     */
    List<AdminInfo> selectByPage(Integer start ,Integer limit);

}

AdminDaolmpl中把函数写完整注意要链接mysql

package S4.dao;

import S4.pojo.AdminInfo;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class AdminDaoImpl implements AdminDao {
    @Override
    public AdminInfo selectByNameAndPwd(String name, String pwd) {
        AdminInfo result = null;

        try {
            Class.forName("com.mysql.jdbc.Driver");// jdbc驱动
            String uri = "jdbc:mysql://localhost:3306/jc0122?useUnicode=ture&serverTimezone=UTC";
            String userid = "root";
            String upwd = "123456";
            Connection connection = DriverManager.getConnection(uri, userid, upwd);

            System.out.println("connection:" + connection);

            //开始查询
            String sql = "SELECT * FROM admin_info WHERE admin_name = ? AND admin_pwd = ?"; //使用?对传入的参数进行占位

            PreparedStatement ps = connection.prepareStatement(sql);
            //参数中 1 表示第一个  name 表示对应的值
            ps.setObject(1, name);
            ps.setObject(2, pwd);

            ResultSet set = ps.executeQuery();

            while (set.next()) {

                AdminInfo adminInfo = new AdminInfo();
                //匹配java对象的属性和数据库对象的字段一一对应起来
                adminInfo.setAdminId(set.getInt("admin_id"));
                adminInfo.setAdminName(set.getString("admin_name"));
                adminInfo.setAdminPwd(set.getString("admin_pwd"));
                adminInfo.setAdminCtime(set.getDate("admin_ctime"));
                adminInfo.setAdminMtime(set.getDate("admin_mtime"));
                adminInfo.setAdminState(set.getInt("admin_state"));
                adminInfo.setRoleId(set.getInt("role_id"));

                result = adminInfo;
                break;
            }


            //后面就是展示到UI上面去


        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }


        return result;
    }

    @Override
    public List<AdminInfo> selectByPage(Integer start, Integer limit) {

        try {
            Class.forName("com.mysql.jdbc.Driver");// jdbc驱动
            String uri = "jdbc:mysql://localhost:3306/jc0122?useUnicode=ture&serverTimezone=UTC";
            String userid = "root";
            String pwd = "123456";
            Connection connection = DriverManager.getConnection(uri,userid,pwd);


            //开始查询
            String sql = "select * from admin_info LIMIT ? , ? ";

            PreparedStatement ps = connection.prepareStatement(sql);

            ps.setObject(1,start);
            ps.setObject(2,limit);
            ResultSet set = ps.executeQuery();
            List<AdminInfo> list = new ArrayList<>();
            while (set.next()){

                AdminInfo adminInfo = new AdminInfo();
                //匹配java对象的属性和数据库对象的字段一一对应起来
                adminInfo.setAdminId(set.getInt("admin_id"));
                adminInfo.setAdminName(set.getString("admin_name"));
                adminInfo.setAdminPwd(set.getString("admin_pwd"));
                adminInfo.setAdminCtime(set.getDate("admin_ctime"));
                adminInfo.setAdminMtime(set.getDate("admin_mtime"));
                adminInfo.setAdminState(set.getInt("admin_state"));
                adminInfo.setRoleId(set.getInt("role_id"));

                list.add(adminInfo);


            }


            return list;




        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }



        return null;
    }
}

最后main函数DaoTest

package S4.test;

import S4.dao.AdminDao;
import S4.dao.AdminDaoImpl;
import S4.pojo.AdminInfo;

import java.util.List;

public class DaoTest {

    public static void main(String[] args) {


        AdminDao adminDao = new AdminDaoImpl();  // 接口类new出实现类

        AdminInfo adminInfo = adminDao.selectByNameAndPwd("zhangsan","123456");
        System.out.println(adminInfo);


        List<AdminInfo> list = adminDao.selectByPage(1,10);
        System.out.println(list);

    }
}

 结果是按账号密码输出了张三按分页查找注意起始是0这里是1输出了李四。

阿里云国内75折 回扣 微信号：monov8
阿里云国际，腾讯云国际，低至75折。AWS 93折 免费开户实名账号 代冲值 优惠多多 微信号：monov8 飞机：@monov6
标签: Java数据库
返回列表

上一篇：如何与他人交流

下一篇：【云原生之Docker实战】在Docker环境部署Answer问答平台

“java入门作业-DAO，读取sql数据库” 的相关文章

Java基础：volatile详解_java volatile1年前 (2023-02-02)
Java动态代理1年前 (2023-02-02)
javamail 发送、读取邮件_51CTO博客_java 发送邮件1年前 (2023-02-02)
33、Java 异常掌握这些就够了（图解 Java 中的异常）1年前 (2023-02-02)
【尚硅谷】Java数据结构与算法笔记10 - 树结构的基础部分1年前 (2023-02-02)
Java数据结构--链表1年前 (2023-02-02)
【Java集合】ArrayList源码分析1年前 (2023-02-02)
java：Cassandra入门与实战——上1年前 (2023-02-02)
Java类的几种修饰符1年前 (2023-02-02)
jsp网络课程管理系统Myeclipse开发mysql数据库web结构java编程计算机网页项目1年前 (2023-02-02)

阿里云国际版