MyBatisPlus简介

1. 无侵入：只做增强不做改变，不会对现有工程产生影响
2. 强大的CRUD操作：内置通用的Mapper，少量配置即可实现CRUD操作
3. 支持Lambda：编写查询条件无需担心字段写错
4. 支持主键自动生成
5. 内置分页插件

所需的依赖

  <dependency>
      <groupId>com.baomidou</groupId>
      <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.4.3</version>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.2.16</version>
</dependency>
<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <scope>runtime</scope>
</dependency>

标准的CRUD操作

1. 首先定义对应的实体类
2. 创建对应的Mapper接口，让其继承于BaseMapper<>
3. 调用内置的CRUD方法

4. 实体类的编写

@Data
@AllArgsConstructor
@NoArgsConstructor
public class UserInfo {
    private int id;
    private String name;
    private int age;

    public UserInfo(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

5. Mapper接口的编写

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

6. 测试类的编写

@SpringBootTest
class Demo1ApplicationTests {

    @Autowired
    public UserMapper userMapper;
    @Test
    public void save(){
        UserInfo user = new UserInfo("jack",20);
        userMapper.insert(user);
    }
    @Test
    public void delete(){
        userMapper.deleteById(3);
    }
    @Test
    public void update(){
        UserInfo userInfo = new UserInfo();
        userInfo.setName("wang");
        userInfo.setId(1);
        userMapper.updateById(userInfo);
    }
    @Test
    public void getOne(){
        System.out.println(userMapper.selectById(1));
    }
    @Test
    public void getAll() {
        System.out.println(userMapper.selectList(null));
    }

}

MyBatisPlus的调试日志

spring:
  datasource:
      url: jdbc:mysql:///mybatis?serverTimeZone=UTC
      username: root
      password: 123456
      driver-class-name: com.mysql.cj.jdbc.Driver
      type: com.alibaba.druid.pool.DruidDataSource
  main:
    banner-mode: off #关闭SpringBoot 的banner
server:
  port: 8080 # 设置服务器的端口号
logging:
  level:
    root: error # 设置SpringBoot的日志为只有报错的时候打印日志


mybatis-plus:
  global-config:
    db-config:
      table-prefix: # 添加表名的前缀
      id-type: auto # 默认的id是采用雪花算法，auto后就是id自增了
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #标准日志输出

MybatisPlus分页操作

1. 创建MybatisPlus配置类

@Configuration
public class MyBatisPlusConfigration {
	//设置分页拦截器
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor(){
        MybatisPlusInterceptor mybatisPlusInterceptor = new MybatisPlusInterceptor();
        mybatisPlusInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return mybatisPlusInterceptor;
    }
}

2. 编写测试方法

 @Test
    void pageQuery(){
        IPage page = new Page(1,3);
        userMapper.selectPage(page,null);
        System.out.println(page.getPages());//总页数
        System.out.println(page.getCurrent());//当前页码
        System.out.println(page.getSize());//当前页的数量
        System.out.println(page.getTotal());//总数
        System.out.println(page.getRecords());//返回的集合
    }

MyBatisPlus条件查询

 @Test
    public void whereQuery(){
        String name = "j";
        LambdaQueryWrapper<UserInfo> queryWrapper = new LambdaQueryWrapper();
        /*
        * param 1: 判断字符是否为null值，可以省略，一但为null那么sql的模糊查询--> %null%
        * param 2: 根据那个字段进行匹配
        * parma 3: 模糊查询的内容
        */
        queryWrapper.like(Strings.isNotEmpty(name),UserInfo::getName,name);
        userMapper.selectList(queryWrapper);
    }