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mybatis-plus:3

mybatis-plus-3初级入门(MP)

一、快速入门

1、Spring Boot 整合

1、pom.xml

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.2.0</version> <!-- mybatis-plus-3版本使用,Spring Boot 2.x -->
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.17</version>
</dependency>

2、application.yml

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/mp?useSSL=false&serverTimezone=GMT%2B8
    username: root
    password: root

3、启动类

@MapperScan("com.demo.dao")
@SpringBootApplication
public class Application {

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

}

4、实体

@Data
public class User {
    
    private Long id;  // 主键
    private String name;  // 姓名
    private Integer age;  // 年龄
    private String email;  // 邮箱
    private Long managerId;  // 直属上级
    private LocalDateTime createTime;  // 创建时间
}

5、dao

public interface UserMapper extends BaseMapper<User> {
    
}

6、测试

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void select(){
        // 参数为null，查询全部
        List<User> users = userMapper.selectList(null);
        // 断言(Assert)：断言的条件如果返回错误，则终止程序执行
        // 判断一下返回的users的长度是否为5
        Assert.assertEquals(5,users.size());
        users.forEach(System.out::println);
    }
    
}

二、通用Mapper

1、新增方法

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void insert(){
        User user = new User();
        user.setName("小明");
        user.setAge("23");
        user.setManagerId("1");
        user.setCreateTime(LocalDateTime.now());
        // 插入单条数据，返回影响记录数
        int rows = userMapper.insert(user);
        System.out.println("影响记录数：" + rows);
    }
    
}

2、常用注解

// 表名称
@TableName("表名")
public class User {
    
    // 主键
    @TableId
    private Long id;  // 主键
    // 指定数据库中对应的列
    @TableField("name")
    private String realName;  // 姓名
    // condition的查询控制
    @TableField(condition=SqlCondition.LIKE)
    private Integer age;  // 年龄
    private String email;  // 邮箱
    private Long managerId;  // 直属上级
    private LocalDateTime createTime;  // 创建时间
}

3、排除非表字段的三种方式

添加关键字transient(不能序列化)

private transient String remark; // 备注

添加关键字static

private static String remark; // 备注

// 省略 get set

@TableField(exist=false)

@TableField(exist=false)
private String remark; // 备注

4、查询

4.1、基本查询

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    // where id = ''
    public void selectById(){
       User user = userMapper.selectById(Id);
    }
    
    @Test
    // where id in ('','','')
    public void selectBatchIds(){
       List<Long> ids = Arrays.asList(id1,id2,id3);
       List<User> users = userMapper.selectBatchIds(Id);
       users.forEach(System.out::println);
    }
    
    @Test
    // where name = '' and age = ''
    public void selectByMap(){
       Map<String,Object> map = new HashMap<>();
       // key是数据库表中的列名
       map.put("name","张三");
       map.put("age","25");
       List<User> users = userMapper.selectByMap(map);
       users.forEach(System.out::println);
    }
    
}

4.2、条件构造器查询

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    // name like '%%' and age < ''
    public void selectList1(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // .like() .lt()：第一个参数都是 数据库表中的字段名
       queryWrapper.like("name","张").lt("age",30);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // name like '%%' and (age between '' and '') and email is not null
    public void selectList2(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // .like() .between() .isNotNull()：第一个参数都是 数据库表中的字段名
       queryWrapper.like("name","张").between("age",20,30).isNotNull("email");
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // name like '张%' or age >= '' order by age desc,id asc
    public void selectList3(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // .likeRight() .ge() .orderByDesc() .orderByAsc()：第一个参数都是 数据库表中的字段名
       queryWrapper.likeRight("name","张").or().ge("age",25).orderByDesc("age")
           		.orderByAsc("id");
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // date_format(create_time,'%Y-%m-%d') and manager_id in (select id from user where name like '王%')
    public void selectList4(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // apply：拼接sql。{0}代表后边的参数的索引。并且避免sql注入。
       queryWrapper.apply("date_format(create_time,'%Y-%m-%d')={0}","2019-02-14")
           .inSql("manager_id","select id from user where name like '王%'");
           		.orderByAsc("id");
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // name like '张%' and (age < ''or email is not null)
    public void selectList5(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();

       queryWrapper.likeRight("name","张")
           .and(
           		qw->qw.lt("age",40).or().isNotNull("email")
       	   );
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // name like '张%' or (age < '' and age > '' and email is not null)
    public void selectList6(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();

       queryWrapper.likeRight("name","张")
           .or(qw->qw.lt("age",40).gt("age",20).isNotNull("email"));
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // (age < '' or email is not null) and name like '张%'
    public void selectList7(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();

       queryWrapper.nested(qw->qw.lt("age",40).or().isNotNull("email"))
           .likeRight("name","张");
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // age in (30,31,34,35)
    public void selectList8(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();

       queryWrapper.in("age",Arrays.asList(30,31,34,35));
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // limit 1
    public void selectList9(){
       // QueryWrapper<User> queryWrapper = Wrappers.<User>query(); 效果与下等同
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // 只能调用一次，多次调用以最后一次为准，有sql注入的风险，请谨慎使用
       queryWrapper.in("age",Arrays.asList(30,31,34,35)).last("limit 1");
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
}

4.3、select 不列出全部字段

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectList1(){

       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // .select()：只查询指定的列
       queryWrapper.select("id","name").like("name","张").lt("age",30);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    public void selectList2(){

       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // .select()：!info.getColumn().equals("create_time")：排除指定列
       queryWrapper
           .select(
           		User.class,info->
           		!info.getColumn().equals("create_time")
           		&& !info.getColumn().equals("manager_id")
       	   );
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
}

4.4、condition作用

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void testCondition(){

       String name = "王";
       String email = "";
       
        
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       // condition：控制加不加入到where条件中
       queryWrapper.like(StringUtils.isNotEmpty(name),"name",name)
           like(StringUtils.isNotEmpty(email),"email",email);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    } 
}

4.5、条件构造器(实体参数)

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectByWrapperEntity(){
        
       User whereUser = new User();
	   whereUser.setName("张三");
       whereUser.setAge(20);
        
       // 将whereUser传入到QueryWrapper
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>(whereUser);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    } 
}

4.6、allEq

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectByWrapperAllEq(){
       Map<String,Object> map = new HashMap<>();
       // key是数据库表中的列名
       map.put("name","张三");
       map.put("age","25");
       
       // 将whereUser传入到QueryWrapper
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
        
       // 默认true，传入Null age is null
       queryWrapper.allEq(map);
        
       // 传入false，值为null被忽略
       queryWrapper.allEq(map,false);
        
       // 过滤掉name列，注意'!'
       queryWrapper.allEq((k,v)->!k.equals("name"),map);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    } 
}

4.7、其他

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectMaps1(){
       
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.like("name","张").lt("age",30);
        
       List<Map<String,Object>> users = userMapper.selectMaps(queryWrapper);
       users.forEach(System.out::println);
    } 
    
    @Test
    // select avg(age) avg_age,min(age) min_age,max(age) max_age
    // from user
    // group by manager_id
    // having sum(age) < 500
    public void selectMaps2(){
       
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.select("avg(age) avg_age","min(age) min_age","max(age) max_age")
           .groupBy("manager_id").having("sum(age)<{0}",500);
        
       List<Map<String,Object>> users = userMapper.selectMaps(queryWrapper);
       users.forEach(System.out::println);
    } 
    
    @Test
    public void selectObjs(){
       
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.like("name","张").lt("age",30);
        
       // 只返回一列数据时使用
       List<Object> users = userMapper.selectObjs(queryWrapper);
       users.forEach(System.out::println);
    } 
    
    @Test
    public void selectCount(){
       
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.like("name","张").lt("age",30);
        
       // 查询记录数
       Integer count = userMapper.selectCount(queryWrapper);
       System.out.print("总记录数：" + count);
    }
    
    @Test
    public void selectOne(){
       
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.like("name","张").lt("age",30);
        
       // 只能查询一条记录或者查询不到。查询多会报错。
       User user = userMapper.selectOne(queryWrapper);
       System.out.print("总记录数：" + count);
    }
}

4.8、lambda条件构造器

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectLambda1(){
       
        // 防误写
        // 构造方式1
       LambdaQueryWrapper<User> queryWrapper = new QueryWrapper<User>().lambda();
        // 构造方式2
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<User>();
        // 构造方式3
        LambdaQueryWrapper<User> queryWrapper = Wrappers.<User>lambdaQuery();
        
       queryWrapper.like(User::getName,"张").lt(User::getAge,30);
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    } 
    
    @Test
    // name like '张%' and (age < ''or email is not null)
    public void selectLambda2(){

       LambdaQueryWrapper<User> queryWrapper = Wrappers.<User>lambdaQuery();

       queryWrapper.likeRight(User::getName,"张")
           .and(
           		qw->qw.lt(User::getAge,40).or().isNotNull(User::getEmail)
       	   );
        
       List<User> users = userMapper.selectList(queryWrapper);
       users.forEach(System.out::println);
    }
    
    @Test
    // name like '张%' and (age < ''or email is not null)
    public void selectLambda3(){

       // 构造方式4：放入 userMapper
       List<User> users = 
           new LambdaQueryChainWrapper<User>(userMapper)
           		.likeRight(User::getName,"张")
           		.and(
           			qw->qw.lt(User::getAge,40).or().isNotNull(User::getEmail)
       	   		).list();
        
       users.forEach(System.out::println);
    }
}

4.9、自定义sql

条件
- 版本 >= 3.0.7

接口中用注解

public interface UserMapper extends BaseMapper<User> {
    
    @Select("select * from user ${ew.customSqlSegment}")
    List<User> selectAll(@Param(Constants.WRAPPER) Wrapper<User> wrapper);
    
}

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectAll(){
       LambdaQueryWrapper<User> queryWrapper = Wrappers.<User>lambdaQuery();
       queryWrapper.likeRight(User::getName,"张")
           .and(
           		qw->qw.lt(User::getAge,40).or().isNotNull(User::getEmail)
       	   );
        
       List<User> users = userMapper.selectAll(queryWrapper);
       users.forEach(System.out::println);
    }
    
}

xml配置

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/mp?useSSL=false&serverTimezone=GMT%2B8
    username: root
    password: root
mybatis-plus:
  mapper-locations:
  - com/mp/mapper/*

<select id="selectAll" resultType="com.mp.entity.User">
	select * from user ${ew.customSqlSegment}
</select>

4.10、分页查询

增加配置类

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

测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectPage(){
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.ge("age",30);
        
       // false 不返回总记录数
       // Page<User> page = new Page<User>(1,2,false);
       Page<User> page = new Page<User>(1,2);
        
       IPage<User> iPage = userMapper.selectPage(page,queryWrapper);
       System.out.println("总页数：" + iPage.getPages());
       System.out.println("总记录数：" + iPage.getTotal());
       List<User> users = iPage.getRecords();
       users.forEach(System.out::println);
    }
    
    @Test
    public void selectMapPage(){
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
        
       Page<User> page = new Page<User>(1,2);
       queryWrapper.ge("age",30);
        
       IPage<Map<String,Object>> iPage = userMapper.selectMapPage(page,queryWrapper);
       System.out.println("总页数：" + iPage.getPages());
       System.out.println("总记录数：" + iPage.getTotal());
       List<Map<String,Object>> users = iPage.getRecords();
       users.forEach(System.out::println);
    }
}

4.11、多表联查时的分页查询

mapper类

public interface UserMapper extends BaseMapper<User> {
    IPage<User> selectUserPage(Page<User> page,@Param(Constants.WRAPPER) Wrapper<User> wrapper);	
}

xml

<select id="selectUserPage" resultType="com.mp.entity.User">
	select * from user ${ew.customSqlSegment}
    left join ...
</select>

测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void selectUserPage(){
       QueryWrapper<User> queryWrapper = new QueryWrapper<User>();
       queryWrapper.ge("age",30);
        
       Page<User> page = new Page<User>(1,2);
       
       IPage<User> iPage = userMapper.selectUserPage(page,queryWrapper);
       System.out.println("总页数：" + iPage.getPages());
       System.out.println("总记录数：" + iPage.getTotal());
       List<User> users = iPage.getRecords();
       users.forEach(System.out::println);
    }
}

5、更新

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void updateById(){
       User user = new User();
       user.setId(id);
       user.setAge(26);
       user.setEmail("zhangsan@baomili.com");
       int rows = userMapper.updateById(user);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void update(){
       UpdateWrapper<User> updateWrapper = new UpdateWrapper<User>();
       updateWrapper.eq("name","李艺伟").eq("age",28);
        
       User user = new User();
       user.setEmail("zhangsan2020@baomili.com");
       user.setAge(27);
       int rows = userMapper.update(user,updateWrapper);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void update2(){
       User whereUser = new User();
       whereUser.setName("张三");

       UpdateWrapper<User> updateWrapper = new UpdateWrapper<User>(whereUser);
        
       User user = new User();
       user.setEmail("zhangsan2020@baomili.com");
       user.setAge(27);
        
       int rows = userMapper.update(user,updateWrapper);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void update3(){
       UpdateWrapper<User> updateWrapper = new UpdateWrapper<User>();
       updateWrapper.eq("name","李艺伟").eq("age",28).set("age",30);
        
       int rows = userMapper.update(null,updateWrapper);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void lambdaUpdate(){
       LambdaUpdateWrapper<User> lambdaUpdate = Wappers.<User>LambdaUpdate();
       lambdaUpdate.eq(User:getName,"张").eq(User::getAge,30).set(User::getAge,31);
        
       int rows = userMapper.update(null,updateWrapper);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void lambdaUpdate(){
       boolean status = new LambdaUpdateChainWrapper<User>(userMapper).
       			.eq(User:getName,"张").eq(User::getAge,30).set(User::getAge,31).update();
        
       System.out.println("是否修改成功：" + status);
    }
}

6、删除

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void deleteById(){
       int rows = userMapper.deleteById(id);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void deleteByMap(){
       Map<String,Object> map = new HashMap<>();
       // key是数据库表中的列名
       map.put("name","张三");
       map.put("age","25");
        
       int rows = userMapper.deleteByMap(map);
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void deleteBacthIds(){
       int rows = userMapper.deleteBacthIds(Arrays.asList(id1,id2,id3));
       System.out.println("影响记录数：" + rows);
    }
    
    @Test
    public void delete(){
       LambdaQueryWrapper<User> lambdaQueryWrapper = Wrappers.<User>lambdaQuery(); 
       lambdaQueryWrapper.eq(User::getName,"张三").eq(User:getAge,31);
        
       int rows = userMapper.delete(lambdaQueryWrapper);
       System.out.println("影响记录数：" + rows);
    }
}

三、ActiveRecord模式

实体类

@Data
// 如果不需要继承父类，则callSuper=false，压制警告
@EqualsAndHashCode(callSuper=false)
public class User extends Model<User> {
    
    private static final long serialVersionUID = 1L;
    
    private Long id;  // 主键
    private String name;  // 姓名
    private Integer age;  // 年龄
    private String email;  // 邮箱
    private Long managerId;  // 直属上级
    private LocalDateTime createTime;  // 创建时间
}

测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserMapper userMapper;
    
    @Test
    public void insert(){
        User user = new User();
        user.setName("小明");
        user.setAge("23");
        user.setManagerId("1");
        user.setCreateTime(LocalDateTime.now());
        // 插入单条数据，返回影响记录数
        boolean status = user.insert();
        System.out.println("是否插入成功：" + status);
    }
    
    @Test
    public void selectById(){
       // 查询出来的是个新对象
       User selectUser = user.selectById(id);
       System.out.println(selectUser);
    }
    
    @Test
    public void selectById2(){
       User user = new User();
       user.setId(id);
       // 查询出来的是个新对象
       User selectUser = user.selectById();
       System.out.println(selectUser);
       System.out.println(user);
    }
    
    @Test
    public void updateById(){
       User user = new User();
       user.setId(id);
       user.setName("小明");
       boolean status = user.updateById();
       System.out.println("是否修改成功：" + status);
    }
    
    @Test
    public void deleteById(){
       User user = new User();
       user.setId(id);
       boolean status = user.deleteById();
       System.out.println("是否删除成功：" + status);
    }
    
    @Test
    public void insertOrUpdate(){
        User user = new User();
        user.setName("小明");
        user.setAge("23");
        user.setManagerId("1");
        user.setCreateTime(LocalDateTime.now());
        // 插入单条数据，返回影响记录数
        boolean status = user.insertOrUpdate();
        System.out.println("是否插入成功：" + status);
    }
}

四、主键策略

1、局部策略

@Data
public class User {
    
    // 主键自增 -- IdType.AUTO
    // 默认策略(跟随全局) -- IdType.NONE
    // UUID -- IdType.UUID
    // 雪花算法的自增ID -- IdType.ID_WORKER_STR
    @TableId(type=IdType.AUTO)
    private Long id;  // 主键
    private String name;  // 姓名
    private Integer age;  // 年龄
    private String email;  // 邮箱
    private Long managerId;  // 直属上级
    private LocalDateTime createTime;  // 创建时间
}

2、全局策略

mybatis-plus:
  global-config:
    db-config:
      id-type: 策略

局部策略优先于全局策略

五、MP配置

配置文档

六、通用service

service

public interface UserService extends IService<User>{
    
}

serviceImpl

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper,User> implements UserService{
    
}

测试类

@RunWith(SpringRunner.class)
@SpringBootTest
public class SimpleTest{
    
    @Autowired
    private UserService userService;
    
    @Test
    public void getOne(){
       // 可多传false，取回多条数据，报警告，取第一条数据。
       User one = userService.getOne(Wrappers.<User>lambdaQuery().gt(User::getAge,25));
       System.out.println(one); // 多个报错
    }  
    
    @Test
    public void getBatch(){
        User user1 = new User();
        user.setName("小明");
        user.setAge("23");
        
        User user2 = new User();
        user.setName("大明");
        user.setAge("23");
        
        List<User> users = Arrays.asList(user1,user2);
        boolean status = userService.saveBatch(users);
        System.out.println(status); // 不报错就返回true
    }
    
    @Test
    public void getBatch2(){
        User user1 = new User();
        user.setName("小明");
        user.setAge("23");
        
        User user2 = new User();
        user.setId("1");	// 多插入一个id
        user.setName("大明2");
        user.setAge("23");
        
        List<User> users = Arrays.asList(user1,user2);
        boolean status = userService.saveOrUpdageBatch(users);
        System.out.println(status); // 不报错就返回true
    }
    
    @Test
    public void chain(){
        List<User> users = userService.lambdaQuery().gt(User::getAge,25).like(User::getName,"张").list();
        users.forEach(System.out::println);
    }
    
    @Test
    public void chain2(){
        boolean status = 	
            userService.lambdaUpdate().eq(User::getAge,25).set(User::getAge,26).update();
        System.out.println(status);
    }
    
    @Test
    public void chain3(){
        boolean status = 	
            userService.lambdaUpdate().eq(User::getAge,25).remove();
        System.out.println(status);
    }
}

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原文地址：https://www.cnblogs.com/luckyzs/p/13174631.html