• 12【MyBatis注解开发】

    文章目录

    三、Mybatis注解开发

    3.1 快速入门

    3.1.1 常用注解说明

    注解功能
    @Insert新增
    @Update更新
    @Delete删除
    @Select查询
    @Result结果集封装
    @Results与@Result 一起使用，封装多个结果集
    @One一对一结果集封装
    @Many一对多结果集封装

    3.1.2 注解实现开发

    • SQL语句：
    DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `birthday` date NULL DEFAULT NULL,
  `sex` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `address` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

INSERT INTO `user` VALUES (1, '张三', '1999-02-04', '男', '佛山');
INSERT INTO `user` VALUES (2, '李四', '1998-01-15', '女', '湛江');

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    • 实体类：
    package com.dfbz.entity;


import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;
import java.util.List;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int  id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;
}

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    • dao接口：
    package com.dfbz.dao;

import com.dfbz.entity.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
public interface UserDao {

    @Select("select * from user where id=#{id}")
    User findById(int id);

    @Select("select * from user")
    List<User> findAll();

    @Insert("insert into user values(null,#{username},#{birthday},#{sex},#{address})")
    void save(User user);

    @Update("update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id}")
    void update(User user);

    @Delete("delete from user where id=#{id}")
    void delete(int id);
}

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    • 加载配置类：

    在这里插入图片描述

    • 测试类：
    package com.dfbz.test;

import com.dfbz.dao.UserDao;
import com.dfbz.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.util.Date;
import java.util.List;

public class Demo01 {

    private SqlSessionFactoryBuilder builder;

    private SqlSessionFactory factory;

    private SqlSession session;

    private UserDao userDao;

    @Before
    public void before() throws IOException {
        builder=new SqlSessionFactoryBuilder();
        factory=builder.build(Resources.getResourceAsStream("SqlMapConfig.xml"));
        session= factory.openSession();
        userDao=session.getMapper(UserDao.class);
    }
    @After
    public void after(){
        session.commit();
        session.close();
    }

    @Test
    public void save(){         //增加
        User user=new User();
        user.setUsername("小龙");
        user.setBirthday(new Date());
        user.setSex("男");
        user.setAddress("广州");
        userDao.save(user);

    }
    @Test
    public void delete(){
        userDao.delete(1);
    }
    @Test
    public void update(){
        User user=new User();
        user.setId(2);
        user.setUsername("张三");
        user.setBirthday(new Date());
        user.setSex("男");
        user.setAddress("广州");
        userDao.update(user);

    }
    @Test
    public void findById(){
        User user = userDao.findById(2);
        System.out.println(user);
    }

    @Test
    public void findAll(){
        List<User> userList = userDao.findAll();
        for (User user : userList) {
            System.out.println(user);
        }
    }
}

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    3.2 注解实现一对一映射

    3.2.1 接口

    • Emp：
    package com.dfbz.entity;

import lombok.Data;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
@Data
public class Emp {
    private Integer id;
    private String name;
    private Integer age;
    private String addr;
    private Double salary;

    // 一个员工属于一个部门
    private Dept dept;
}

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    • Dept：
    package com.dfbz.entity;

import lombok.Data;

import java.util.List;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
@Data
public class Dept {
    private Integer id;
    private String name;
    private String location;

    // 一个部门下有多个员工
    private List<Emp> empList;
}

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    • DeptDao：
    package com.dfbz.dao;


import com.dfbz.entity.Dept;
import org.apache.ibatis.annotations.Select;

public interface DeptDao {

    @Select("select * from dept where id=#{id}")
    Dept findById(Integer id);
}

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    • EmpDao：
    package com.dfbz.dao;


import com.dfbz.entity.Dept;
import com.dfbz.entity.Emp;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.mapping.FetchType;

public interface EmpDao {


    @Select("select * from emp where id=#{id}")
    @Results({
            @Result(id = true, property = "id", column = "id"),
            @Result(property = "name", column = "name"),
            @Result(property = "age", column = "age"),
            @Result(property = "addr", column = "addr"),
            @Result(property = "salary", column = "salary"),
            @Result(property = "dept", column = "dept_id", javaType = Dept.class,
                    one = @One(select = "com.dfbz.dao.DeptDao.findById",fetchType = FetchType.LAZY)
            ),

    })
    Emp findById(Integer id);
}

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    3.2.2 测试类

    @Test
public void test1() {
    Emp emp = empDao.findById(1);
    System.out.println(emp);
}

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    3.3 注解实现一对多映射

    3.2.1 接口

    • DeptDao：
    @Select("select * from dept where id=#{id}")
@Results({
        @Result(id = true,property = "id",column = "id"),
        @Result(property = "name",column = "name"),
        @Result(property = "location",column = "location"),
        @Result(property = "empList",column = "id",javaType = List.class,
            many = @Many(select = "com.dfbz.dao.EmpDao.findByDeptId",fetchType = FetchType.LAZY)
        )
})
Dept findDeptAllById(Integer id);

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    • EmpDao：
    @Select("select * from emp where dept_id=#{deptId}")
List<Emp> findByDeptId(Integer deptId);

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    3.2.2 测试类

    @Test
public void test2() {
    Dept dept = deptDao.findDeptAllById(1);
    System.out.println(dept);
}

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  • 原文地址：https://blog.csdn.net/Bb15070047748/article/details/128103156