Mybatis-Plus入门（Mapper CRUD接口）

Mybatis-plus是在Mybatis的基础上做增强，为简化开发而生

• 只做增强不做改变，引入它不会对现有工程产生影响，如丝般顺滑。
• 只需简单配置，即可快速进行 CRUD 操作，从而节省大量时间。
• 热加载、代码生成、分页、性能分析等功能一应俱全。

官网文档

环境搭建（Springboot）

建表

CREATE TABLE `t_hero`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `neck_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `create_time` datetime(0) NULL DEFAULT NULL,
  `update_time` datetime(0) NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 4 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

导入依赖

<dependency>
     <groupId>org.springframework.bootgroupId>
     <artifactId>spring-boot-starterartifactId>
dependency>
    
<dependency>
    <groupId>mysqlgroupId>
    <artifactId>mysql-connector-javaartifactId>
    <scope>runtimescope>
dependency>

<dependency>
    <groupId>com.baomidougroupId>
    <artifactId>mybatis-plus-boot-starterartifactId>
    <version>3.3.2version>
dependency>

<dependency>
    <groupId>org.projectlombokgroupId>
    <artifactId>lombokartifactId>
    <optional>trueoptional>
dependency>

<dependency>
    <groupId>org.springframework.bootgroupId>
    <artifactId>spring-boot-starter-testartifactId>
    <scope>testscope>
<dpendency>

application.yml配置文件

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
    driver-class-name: com.mysql.cj.jdbc.Driver
    
mybatis-plus:
  mapper-locations: classpath:/mapper/*.xml
  global-config:
    db-config:
      id-type: auto  
      table-prefix: t_
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

实体类

@Data
public class Hero {
    private int id;
    private String name;
    private String neckName;
    @TableField(fill = FieldFill.INSERT)
    private Date createTime;
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;
}

mapper接口

@Component
public interface HeroMapper extends BaseMapper<Hero> {
}

---

开始测试

INSERT

//添加操作，参数是一个实体类
int insert(T entity);

//测试
@Test
void testInsert(){
    int insert = heroMapper.insert(new Hero("史蒂夫", "美国队长"));
    System.out.println("添加的数据条数："+insert);
}
//SQL日志
/* ==>  Preparing: INSERT INTO t_hero ( name, neck_name, create_time, update_time ) VALUES ( ?, ?, ?, ? )
   ==> Parameters: 史蒂夫(String), 美国队长(String), 2020-07-29 10:39:24.823(Timestamp), 2020-07-29 10:39:24.823(Timestamp)
   <==    Updates: 1
*/

DELETE

// 根据自定义条件构造删除
int delete(@Param(Constants.WRAPPER) Wrapper<T> wrapper);
//根据ID 批量删除，参数为list
int deleteBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);
// 根据 ID 删除
int deleteById(Serializable id);
// 根据map删除，传入值为map，map的key对应表中的字段
int deleteByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);

//测试
@Test
void testDeleteBatchIds(){
    int i = heroMapper.deleteBatchIds(Arrays.asList(new Integer[]{1, 2, 3}));
    System.out.println("删除的数据条数："+i);
}
/**
 * ==>  Preparing: DELETE FROM t_hero WHERE id IN ( ? , ? , ? ) 
 * ==> Parameters: 1(Integer), 2(Integer), 3(Integer)
 * <==    Updates: 3
 */

@Test
void testDelete(){
    QueryWrapper<Hero> queryWrapper = new QueryWrapper<>();
    queryWrapper.gt("id",1)
            .likeLeft("neck_name","战士");
    heroMapper.delete(queryWrapper);
}
/**
 * ==>  Preparing: DELETE FROM t_hero WHERE (id > ? AND neck_name LIKE ?) 
 * ==> Parameters: 1(Integer), %战士(String)
 * <==    Updates: 1
 */

UPDATE

// 根据id更新，参数为实体类，只更新不为空的属性（字段）
int updateById(@Param(Constants.ENTITY) T entity);

//测试
@Test
void testUpdateById(){
    Hero hero = new Hero(1,"Tony");
    heroMapper.updateById(hero);
}
/**
 * ==>  Preparing: UPDATE t_hero SET name=?, update_time=? WHERE id=? 
 * ==> Parameters: Tony(String), 2020-07-29 11:00:07.754(Timestamp), 1(Integer)
 * <==    Updates: 1
 */

SELECT

// 根据 wrapper 条件，查询一条记录
T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 根据 wrapper 条件，查询全部记录
List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 根据 Wrapper 条件，查询总记录数
Integer selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
// 查询（根据 columnMap 条件）
List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
// 根据 entity 条件，查询全部记录（并翻页）
IPage<T> selectPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

//测试
@Test
void testSelectList(){
    List<Hero> list = heroMapper.selectList(new QueryWrapper<Hero>().gt("id", 1));
    list.forEach(hero -> System.out.println(hero));
}
/**
 * ==>  Preparing: SELECT id,name,neck_name,create_time,update_time FROM t_hero WHERE (id > ?)
 * ==> Parameters: 1(Integer)
 * <==    Columns: id, name, neck_name, create_time, update_time
 * <==        Row: 4, 史蒂夫, 美国队长, 2020-07-29 02:39:25, 2020-07-29 02:39:25
 * <==        Row: 5, Thor, 雷神, 2020-07-16 11:08:54, 2020-07-31 11:08:56
 * <==        Row: 6, Loki, 洛基, 2020-07-23 11:09:18, 2020-07-30 11:09:21
 * <==      Total: 3
 */

@Test
void testSelectCount(){
    Integer count = heroMapper.selectCount(new QueryWrapper<Hero>().gt("id", 1));
    System.out.println("数据总数："+count);
}
/**
 * ==>  Preparing: SELECT COUNT( 1 ) FROM t_hero WHERE (id > ?)
 * ==> Parameters: 1(Integer)
 * <==    Columns: COUNT( 1 )
 * <==        Row: 3
 * <==      Total: 1
 */

@Test
void testSelectOne(){
    QueryWrapper<Hero> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("id",1)
            .eq("name","Tony");
    Hero hero = heroMapper.selectOne(queryWrapper);
}
/**
 * ==>  Preparing: SELECT id,name,neck_name,create_time,update_time FROM t_hero WHERE (id = ? AND name = ?)
 * ==> Parameters: 1(Integer), Tony(String)
 * <==    Columns: id, name, neck_name, create_time, update_time
 * <==        Row: 1, Tony, 钢铁侠, 2020-07-16 10:51:38, 2020-07-29 03:00:08
 * <==      Total: 1
 */

@Test
void testSelectPage(){		  
    //limit 0,2 ,分页插件配置参考下文
    IPage<Hero> page = new Page<>(0,2);
    IPage<Hero> data = heroMapper.selectPage(page, new QueryWrapper<Hero>().lt("id",10));
    data.getRecords().forEach(hero -> System.out.println(hero));
}
/**
 ==>  Preparing: SELECT id,name,neck_name,create_time,update_time FROM t_hero WHERE (id < ?) LIMIT ?,?
 ==> Parameters: 10(Integer), 0(Long), 2(Long)
 */

@Test
void testSelectByMap(){
    Map<String,Object> map= new HashMap<>();
    map.put("id",1);
    map.put("name","Thor");
    List<Hero> list = heroMapper.selectByMap(map);
}
/**
 * ==>  Preparing: SELECT id,name,neck_name,create_time,update_time FROM t_hero WHERE name = ? AND id = ? 
 * ==> Parameters: Thor(String), 1(Integer)
 */

分页插件配置

@Configuration
public class MybatisPlusConfig {
    @Bean
    public PaginationInterceptor paginationInterceptor(){
        return new PaginationInterceptor();
    }
}

自动填充处理器

//设置fill为FieldFill枚举类型
//共四种类型：DEFAULT,INSERT,UPDATE,INSERT_UPDATE;
@TableField(fill = FieldFill.INSERT)
private Date createTime;
@TableField(fill = FieldFill.INSERT_UPDATE)
private Date updateTime;

/**
* 添加时间自动填充配置
* insertFill() : 插入时
* updateFill() : 更新时
*/
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    @Override
    public void insertFill(MetaObject metaObject) {
        this.setFieldValByName("createTime",new Date(),metaObject);
        this.setFieldValByName("updateTime",new Date(),metaObject);
    }

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