依赖

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
//    implementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter:2.1.2'
    implementation('com.baomidou:mybatis-plus-boot-starter:3.1.0')
    implementation('com.baomidou:mybatis-plus-generator:3.1.0')

    compileOnly 'org.projectlombok:lombok'
    runtimeOnly 'mysql:mysql-connector-java'
    annotationProcessor 'org.projectlombok:lombok'
    testImplementation('org.springframework.boot:spring-boot-starter-test') {
        exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
    }
}

• 主要是mybatis-plus-boot-starter这个注解，里面包含了mybatis，不需要重复引入

配置文件

server:
  port: 10000


spring:
  datasource:
    url: jdbc:mysql://localhost:3307/JLCredit
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis-plus:
  #mapper的xml文件所在
  mapper-locations: classpath:mapper/*.xml
  configuration:
    #开启驼峰命名
    map-underscore-to-camel-case: true

• 普通的连接mysql数据库
• mybatis若要在xml文件中写sql，需要注意xml文件位置，这里是直接放在了resources/mapper路径下

开启事务

@EnableTransactionManagement
@SpringBootApplication
public class MybatisPlusApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisPlusApplication.class, args);
    }

}

使用

配置

@Configuration
public class MyBatisPlusConfig {

    /**
     * mybatis-plus SQL执行效率插件【生产环境可以关闭】
     */
    @Bean
    public PerformanceInterceptor performanceInterceptor() {
        return new PerformanceInterceptor();
    }
    /**
     * 分页插件
     */
    @Bean
    public PaginationInterceptor paginationInterceptor() {
        return new PaginationInterceptor();
    }

}

• performanceInterceptor在开启之后每次使用mybatis-plus会打印出执行的sql语句
• paginationInterceptor则是分页工具

实体类

@Data
@TableName("user")
public class UserEntity implements Serializable {

    @TableId
    private String username;

    private String id;

    private String name;

    private String phone;


    @TableField(fill = FieldFill.INSERT) // 创建记录的时候需要填充
    private Date createTime;

    @TableField(fill = FieldFill.INSERT_UPDATE) // 创建和修改的时候都需要填充
    private Date updateTime;

}

• 实体类@TableName映射表名
• @TableField的自动填充通过以下配置实现创建时间和修改时间的插入与更新：

@Component
public class MyMetaObjectHandler implements MetaObjectHandler {

    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime", new Date(), metaObject);
    }

    @Override
    public void updateFill(MetaObject metaObject) {
        this.setFieldValByName("updateTime", new Date(), metaObject);
    }

}

mapper

@Mapper
public interface UserMapper extends BaseMapper<UserEntity> {

    UserEntity getUserById(@Param("id") String id);

    IPage<UserEntity> getUserPage(Page<?> page);

}

server

public interface UserServer extends IService<UserEntity> {


     UserEntity getUserById(String id);

     IPage<UserEntity> getUserPage(Page<UserEntity> page);
     
     void saveUser(UserEntity userEntity);
}

serverImpl

@Service
public class UserServerImpl extends ServiceImpl<UserMapper, UserEntity> implements UserServer {


    @Override
    public UserEntity getUserById(String id) {
        return baseMapper.getUserById(id);
    }

    @Override
    public IPage<UserEntity> getUserPage(Page<UserEntity> page) {
        return baseMapper.getUserPage(page);
    }


    @Transactional
    @Override
    public void saveUser(UserEntity userEntity) {
        save(userEntity);
    }

}

• 在编写完实体类，以及实体类对应的mapper，server，serverImpl之后，就可以使用这个server对该实体所映射的表进行增删改查的操作，mybatisplus提供的操作类基本满足了所有单表的需求，但是多表查询依旧建议自己写个sql
• 自己写原生sql有两种，一种是通过@Select，@Updata，@Delete，@Insert在mapper中写，要么就编写xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ladyishenlong.mybatisplus.mapper.UserMapper">


    <select id="getUserById" resultType="com.ladyishenlong.mybatisplus.model.UserEntity">
        select i.name from user i where i.id = #{id}
    </select>

    <select id="getUserPage" resultType="com.ladyishenlong.mybatisplus.model.UserEntity">
                select i.name from user i
    </select>

</mapper>

查询

    @Autowired
    private UserServer userServer;


    @GetMapping
    public Object test() {

        //分页查询
        IPage<UserEntity> page = new Page<>();
        page.setCurrent(0); //当前页
        page.setSize(1);    //每页条数
        userServer.page(page, new QueryWrapper<UserEntity>().lambda()
                .eq(UserEntity::getId, "666"));

        //xml分页查询
        Page<UserEntity> userEntityPage = new Page<>();
        userEntityPage.setCurrent(0);
        userEntityPage.setSize(1);
        IPage<UserEntity> userEntityIPage = userServer.getUserPage(userEntityPage);


        //xml语句
        userServer.getUserById("666");
        //自动生成查询
        userServer.list(new QueryWrapper<UserEntity>().lambda()
                .eq(UserEntity::getId, "666"));


        return userEntityIPage;

    }

• 这里的分页也可用于xml中自己写的查询语句

插入

    @Autowired
    private UserServer userServer;


    @GetMapping("/test2")
    public Object test2() {

        //插入数据，可以添加事务
        UserEntity userEntity = new UserEntity();
        userEntity.setId("2500");
        userEntity.setName("黑魔导");
        userEntity.setPhone("2500");
        userEntity.setUsername("2500");
        userServer.saveUser(userEntity);
        
        return "";
    }