MyBatisPlus

MyBatisPlus

导入坐标

SpringBoot并没有收录mybatisplus，所以需要自己导入坐标

<dependency>
        <groupId>com.baomidou</groupId>
         <artifactId>mybatis-plus-boot-starter</artifactId>
         <version>3.4.3</version>
</dependency>

# 数据源
<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.23</version>
</dependency>

配置文件

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.NonRegisteringDriver
    url: jdbc:mysql://127.0.0.1:3306/mybatisplus_db?serverTimezone=UTC
    username: root
    password: root
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Long id;
    private String name;
    private String password;
    private Integer age;
    private String tel;
}

mapper

继承mybatisplus的basemapper

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.freshman.entity.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> {
}

测试功能

 @Autowired
    private UserMapper userMapper;

    @Test
    void testSelectAll() {
        List<User> userList = userMapper.selectList(null);
        System.out.println(userList);
    }

以上就是mybatispuls一个入门案例

---

概述

mybatisplus是基于mybatis框架基础上开发的增强型工具，旨在简化开发、提高效率

官网: https://mybatis.plus/ https://mp.baomidou.com/

标准数据层CRUD功能

功能	MP接口
新增	int insert(T t)
删除	int deleteById(Serializable id)
修改	int updateById(T t)
根据id查询	T selectById(Serializable id)
查询全部	List selectList()
分页查询	IPage selectPage(IPage page)
按条件查询	IPage selectPage(Wrapper queryWrapper)

讲一下分页查询

1. 配置分页查询拦截器

   @Configuration
   public class MpConfig {
   
       @Bean
       public MybatisPlusInterceptor mybatisPlusInterceptor(){
           MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
           mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
           return mybatisPlusInterceptor;
       }
   }
   

2. 测试

    @Test
       void testPage(){
           // select * from user limit 1,2;
           IPage<User> userPage = new Page<>(1,2);
           userMapper.selectPage(userPage,null);
           System.out.println("当前页码值：" + userPage.getCurrent());
           System.out.println("每页显示数：" + userPage.getSize());
           System.out.println("一共多少页：" + userPage.getPages());
           System.out.println("一共多少条数据：" + userPage.getTotal());
           System.out.println("要查询到的数据：" + userPage.getRecords());
       }
   
   /**
   ==>  Preparing: SELECT id,name,password,age,tel FROM user LIMIT ?
   ==> Parameters: 2(Long)
   <==    Columns: id, name, password, age, tel
   <==        Row: 1, zhangsan, 123, 12, null
   <==        Row: 2, lisi, 123, 12, null
   <==        Total: 2
   */
   

   

   

条件查询：

1. lambdaquerywrapper

   @Test
       void testSelect(){
           LambdaQueryWrapper<User> wrapper = new LambdaQueryWrapper<>();
           // SELECT id,name,password,age,tel FROM user WHERE (age > ?)
           wrapper.gt(User::getAge,11);
           List<User> users = userMapper.selectList(wrapper);
           System.out.println(users);
       }
   
   /**
   ==>  Preparing: SELECT id,name,password,age,tel FROM user WHERE (age > ?)
   ==> Parameters: 11(Integer)
   <==    Columns: id, name, password, age, tel
   <==        Row: 1, zhangsan, 123, 12, 123
   <==        Row: 2, lisi, 123, 12, 123
   <==        Row: 3, wangwu, 123, 12, 123
   <==      Total: 3
   */
   

   更多方法：https://mybatis.plus/guide/wrapper.html#abstractwrapper

2. 字段映射和表名映射

   // 设计表的名称
   @TableName("tbl_user")
   public class User{
       private Long id;
       private String name;
       // 在数据表中为pwd,且查询时不参与查询 即 selct id name from user;没有pwd
       @TableField(value = "pwd",select = false)
       private String password;
       // 数据库中不存在这个字段
       @TableField(exist = false)
       private Integer online;
   }
   

3. id生成策略

   AUTO(0)	使用数据库id自增策略控制id生成
   NONE(1)	不设置id生成策略
   INPUT(2)	用户手工输入id
   ASSIGN_ID(3)	雪花算法生成id(可兼容数值型和字符串型)
   ASSIGN_UUID(4)	以UUID生成算法作为id生成策略

   雪花算法

   

   public class User{
       @TableId(type = IdType.AuTo)
       private Long id;
   }
   

4. 逻辑删除

   为数据设置是否可用状态字段，删除时设置状态字段为不可用状态，数据保留在数据库中

   // value 为 默认不删除的值  delval 为 默认删除的值
   @TableLogic(value = "0",delval = "1")
    private Integer deleted;
   
   ==>  Preparing: UPDATE user SET deleted=1 WHERE id=? AND deleted=0
   ==> Parameters: 1(Long)
   <==    Updates: 1
   

   

5. 全局配置

   mybatis-plus:
     configuration:
       log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
     global-config:
       db-config:
         id-type: assign_id
         logic-delete-field: deleted
         logic-delete-value: 1
         logic-not-delete-value: 0
   

6. 乐观锁

   1. 配置拦截器

      @Configuration
      public class MpConfig {
          @Bean
          public MybatisPlusInterceptor mybatisPlusInterceptor(){
              // 1、定义拦截器
              MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
              // 2、添加分页拦截器
              mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
              // 3、添加乐观锁拦截器
              mybatisPlusInterceptor.addInnerInterceptor(new OptimisticLockerInnerInterceptor());
              return mybatisPlusInterceptor;
          }
      }
      

   2. 设置version

      @Version
      private Integer version;
      

   3. 测试方法

       	@Test
          void testUpdate(){
              User user = new User();
              user.setId(3L);
              user.setName("ligeng");
              user.setVersion(1);
              userMapper.updateById(user);
          }
      
      
      /**
      ==>  Preparing: UPDATE user SET name=?, version=? WHERE id=? AND version=? AND deleted=0
      ==> Parameters: ligeng(String), 2(Integer), 3(Long), 1(Integer) 这里第二个参数为2，即执行了version = version + 1
      <==    Updates: 1
      */
      

7. 代码生成器 （使用mybatisx插件生成即可）