MybatisPlus学习笔记(一)之基本使用

简单介绍

MybatisPlus是一个Mybatis的整强工具包。

代码

#创建库
create database mp;
use mp;
#使用表
create table  mp(
    id int primary key auto_increment,
    last_name varchar(50),
    email varchar(50),
    gender char(1),
    age int
);
insert into mp(last_name, email, gender, age) values ('Tom','tom@163.com',1,1);
insert into mp(last_name, email, gender, age) values ('Jerry','Jerry@163.com',1,1);
insert into mp(last_name, email, gender, age) values ('Black','Black@163.com',1,1);
insert into mp(last_name, email, gender, age) values ('White','White@163.com',1,1);
select * from mp;

 pom.xml依赖引入

        
        
            com.baomidou
            mybatis-plus-boot-starter
            3.5.1
        

    org.springframework.boot
    spring-boot-starter-web
    
        
            org.springframework.boot
            spring-boot-starter-logging
        
    

        
        
            mysql
            mysql-connector-java
        

 application.yml

server:
    port: 7000
spring:
    datasource:
        driver-class-name: com.mysql.cj.jdbc.Driver
        password: root
        url: jdbc:mysql://127.0.0.1:3306/mp?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
        username: root

mybatis-plus:
    #type-aliases-package: com.monster.demo.entity
    global-config:
        db-config:
            id-type: assign_uuid  # 鼠标放在id-type上面显示的解释如下图。

统一CURD的使用

Mapper包XxxMapper.java

/*
* Mapper接口
* 基于Mybatis: 在Mapper接口中编写CRUD相关的方法,提供Mapper接口对应的SQL映射文件以及方法对应的SQL语句
*
* 基于MP: 让XxxMapper接口继承BaseMapper接口即可
*         BaseMapper：泛型指定的就是当前Mapper接口所操作的实体类类型
* */
@Mapper
public interface MpMapper extends BaseMapper {
}

实体类Employee层

/*
* 实体类
* MybatisPlus会默认使用实体类的类名到数据库中找对应的表
* */
@Data
@TableName("mp")
public class MpEmployee {
    /*
    * @TableId
    *  value: 指定表中的主键列的列明,入股实体属性名与列名一致,可以省略不指定
    *  type: 指定主键策略
    * */
    @TableId(value = "id",type = IdType.AUTO)
    private Integer id;

　　@TableField(value = "last_name")
　　private String lastName;

    private String email;
    private Integer gender;
    private Integer age;

}

Test测试

@SpringBootTest
@Slf4j
class MybatisplusApplicationTests {
    @Autowired
    private MpMapper mapper;
/*
插入
*/
    @Test
    void contextLoads() {
        //初始化Employee对象
        MpEmployee employee = new MpEmployee();
        employee.setLastName("张三");
        employee.setEmail("张三@163.com");
        employee.setGender(1);
        employee.setAge(22);
        employee.setSalary(20000.0);
        //插入到数据库
        int insert = mapper.insert(employee);
        log.info("insert"+insert);

        //获取当前数据在数据库中的主键值
        Integer key = employee.getId();
        System.out.println("key"+key);
    }

}

 修改操作测试总结

/*根据id修改*/
@Test
void testUpload(){
    //初始化Employee对象
    MpEmployee employee = new MpEmployee();
    employee.setId(1);
    employee.setLastName("萧瑟");
    employee.setEmail("xiao@163.com");
    employee.setGender(0);
    employee.setAge(44);
    int result = mapper.updateById(employee);
    System.out.println("修改成功:"+result);
}

//根据条件更新修改
@Test
void testUpdate(){
    MpEmployee employee = new MpEmployee();
    employee.setGender(0);
    employee.setAge(20);
    QueryWrapper wrapper = new QueryWrapper<>();
    wrapper.eq("last_name","张三");
    //根据条件做更新匹配lastName="张三"
    int update = mapper.update(employee, wrapper);
    System.out.println("修改成功:"+update);
}

//根据多个条件更新修改
@Test
void testUpdate(){
    MpEmployee employee = new MpEmployee();
    employee.setEmail("cs@163.com");
    employee.setSalary(10.0);
    QueryWrapper wrapper = new QueryWrapper<>();
    wrapper.eq("gender",0).eq("age",20);
    //根据条件做更新匹配lastName="张三"
    int update = mapper.update(employee, wrapper);
    System.out.println("修改成功:"+update);
}

 删除操作

   /*
    * 根据ID删除
    * */
    @Test
    void deleteTest(){
        int delete = this.mapper.deleteById(7L);
        System.out.println("删除成功:"+delete);
    }

/*
根据map删除数据,多条件之间是and关系
*/

@Test
void testDeleteByMap(){
    HashMap map = new HashMap<>();
    map.put("last_name","张三");
    map.put("age",20);
    int delete = this.mapper.deleteByMap(map);
    System.out.println("删除成功:"+delete);
}

 /*
删除方法
*/

   @Test
    void testDelete(){

        //用法一
//        QueryWrapper wrapper = new QueryWrapper<>();
//        wrapper.eq("last_name","张三")
//                .eq("age",22);
        //用法二
        MpEmployee employee = new MpEmployee();
        employee.setLastName("张三");
        employee.setAge(20);
        QueryWrapper wrapper = new QueryWrapper<>(employee);
        
        
        //根据包装条件做条件
        int delete = this.mapper.delete(wrapper);
        System.out.println("删除成功:"+delete);
    }

/*
* 批量删除
* */
@Test
void testDeleteBatchIds(){
    this.mapper.deleteBatchIds(Arrays.asList(8L,9L,10L));
}

 查询

/*
* 通用 查询操作
* */

@Test
void testSelectById(){
    MpEmployee select = this.mapper.selectById(1L);
    System.out.println("查询成功:"+select);
}

/*
* 通用 查询多个操作
* */

@Test
void testSelectBatchIds(){
    List employees = this.mapper.selectBatchIds(Arrays.asList(2L, 3L, 4L));
    for (MpEmployee employee : employees) {
        System.out.println(employee);
    }
}

 /*
根据条件查询一个
*/

@Test
void testSelectOne(){
    QueryWrapper wrapper = new QueryWrapper<>();
    //查询条件
    wrapper.eq("last_name","张三");
    MpEmployee employee = this.mapper.selectOne(wrapper);
    System.out.println(employee);
}

 /*查询统计*/

@Test
void  testSelectCount(){
    QueryWrapper wrapper = new QueryWrapper<>();
    wrapper.gt("age",10);//年龄大于20岁的用户
    //根据用户查询条数
    Long count = this.mapper.selectCount(wrapper);
    System.out.println("查询条件:"+count);
}

 
/*查询多个*/

@Test
void testSelectList(){
    QueryWrapper wrapper = new QueryWrapper<>();
    //设置查询条件
    wrapper.like("email","xiao@163.com");
    List list = this.mapper.selectList(wrapper);
    for (MpEmployee mpEmployee : list) {
        System.out.println(mpEmployee);
    }
}