MyBatis-Plus梳理

@Mapper //这块不标注,就需要引导类进行 mapper 的扫描
public interface PersionMapper extends baseMapper {
}

六 mp的Service:

用不用这个Service看我们自己,若是我们不需要在Service中做业务处理,只是中转调用,直接使用mp提供的即可,否则我们自己写Service做相关的业务处理,mp的Service实现:

1 定义接口继承IService接口

2 定义实现类继承ServiceImpl,然后实现定义的接口即可:

示例:

接口:

public interface PersionService extends IService {
}

实现类:

@Service
public class PersionServiceImp extends ServiceImplimplements PersionService {
}

在使用 mybatisplus 的分页查询时必须配置拦截器, 否则无法实现分页的拦截:

直接粘贴,谁写都一样,没有任何的技术含量:

@Configuration
public class PageConfig {

    
   

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

关于分页查询,下面做方法调用时候解释

 示例:

@Component
public class MymetaObjectHandler implements metaObjectHandler {
    
    @Override
    public void insertFill(metaObject metaObject) {

//根据 getFieldValByName 方法将 mataObject 对象(其实就是一个个使用@TableField注解标注的属性的集合),指定属性检测赋值请款
        Object created = getFieldValByName("createdate", metaObject);
//如果 created 字段为空进行自动填充.(如果不为空,忽略)
        if (null == created) {
//为该属性赋值设置自动填充数据
            setFieldValByName("createdate", new Date(), metaObject);
        }
        Object updated = getFieldValByName("updatedate", metaObject);
//如果 update 字段为空进行自动填充.(如果不为空,忽略)
        if (null == created) {
//为该属性赋值设置自动填充数据
            setFieldValByName("updatedate", new Date(), metaObject);
        }
    }

    @Override
    public void updateFill(metaObject metaObject) {
        
        //只要改属性有变动就自动实现
        setUpdateFieldValByName("updatedate", new Date(), metaObject);
        strictUpdateFill(metaObject, "updateTime", LocalDateTime.class, LocalDateTime.now());
        fillStrategy(metaObject, "updateTime", LocalDateTime.now());
    }
}

没啥好说的,直接看例子吧!

@SpringBootTest
@RunWith(SpringRunner.class)
class UserMapperTest {
@Autowired
private UserMapper userMapper;

@Test
public void testSelectById() {
User user = userMapper.selectById(1L);
System.out.println(user);
}

@Test
public void testInsert() {
User user = new User();
//user.setId(6L);
user.setUserName("zahnsgan");
user.setPassword("root123");
int count = userMapper.insert(user);
System.out.println(count);
}

@Test
public void testDelete() {


//3. 根据 map 构造条件，删除
Map map = new HashMap<>();
//delete from tb_user where user_name = ? and age = ?
map.put("user_name","zhangsan");
map.put("age","18");
userMapper.deleteByMap(map);} }

@Test
public void testUpdateById() {
User user = new User();
user.setId(2L);
user.setPassword("1111111");
int count = userMapper.updateById(user);
}

@Test
public void testSelectPage() {
int current = 1;//当前页码
int size = 2;//每页显示条数
IPage page = new Page(current,size);
userMapper.selectPage(page,null);
List records = page.getRecords();//当前页的数据
long pages = page.getPages();//总页数 2
long total = page.getTotal();//总记录数 4
System.out.println(records);
System.out.println(pages);
System.out.println(total);
}
}

条件构造器:

基本的运算符号和对应的方法:

eq( ) :  等于 =
ne( ) :  不等于 <>
gt( ) :  大于 >
ge( ) :  大于等于  >=
lt( ) :  小于 <
le( ) :  小于等于 <=
between ( ) :  BETWEEN 值1 AND 值2 
notBetween ( ) :  NOT BETWEEN 值1 AND 值2 
in( ) :  in
notIn( ) ：not in

条件构造器查询
@SpringBootTest
@RunWith(SpringRunner.class)
public class WrapperTest {
@Autowired
private UserMapper userMapper;

@Test
public void testWrapper1() {
//1.创建查询条件构建器
QueryWrapper wrapper = new QueryWrapper<>();
//2.设置条件
wrapper.eq("user_name", "lisi")
.lt("age", 23)
.in("name", "李四", "王五");

List users = userMapper.selectList(wrapper);
System.out.println(users);
}
@Test
public void testWrapper2() {
//1.创建查询条件构建器
QueryWrapper wrapper = new QueryWrapper<>();
//2.设置条件
wrapper.eq("user_name", "lisi")
.or()
.lt("age", 23)
.in("name", "李四", "王五");

List users = userMapper.selectList(wrapper);
System.out.println(users);
}

@Test
public void testWrapper3() {
//1.创建查询条件构建器
QueryWrapper wrapper = new QueryWrapper<>();
//2.设置条件
wrapper.likeLeft("user_name", "zhang");

List users = userMapper.selectList(wrapper);
System.out.println(users);
}

@Test
public void testWrapper4() {
//1.创建查询条件构建器
QueryWrapper wrapper = new QueryWrapper<>();
//2.设置条件
wrapper.eq("user_name", "lisi")
.or()
.lt("age", 23)
.in("name", "李四", "王五")
//.orderBy(true,true,"age")
.orderByDesc("age"); //倒序查询.顺序为 asc

List users = userMapper.selectList(wrapper);
System.out.println(users);
}

@Test
public void testWrapper5() {
//1.创建查询条件构建器
QueryWrapper wrapper = new QueryWrapper<>();
//2.设置条件
wrapper.eq("user_name", "lisi")
.or()
.lt("age", 23)
.in("name", "李四", "王五")
//.orderBy(true,true,"age")
.orderByDesc("age")
.select("id", "user_name");

List users = userMapper.selectList(wrapper);
System.out.println(users);
}

@Test
public void testWrapper6() {
int current = 1;//当前页码
int size = 2;//每页显示条数
//1. 构建分页对象
Page page = new Page<>(current, size);
//2. 构建条件对象
QueryWrapper wrapper = new QueryWrapper();
wrapper.lt("age", 23);
userMapper.selectPage(page, wrapper);
List records = page.getRecords();
long total = page.getTotal();
long pages = page.getPages();
System.out.println(records);
System.out.println(total);//2
System.out.println(pages);//1
}

@Test
public void testWrapper7() {
LambdaQueryWrapper wrapper = new LambdaQueryWrapper<>();
wrapper.eq(User::getUserName, "zhangsan");
User user = userMapper.selectOne(wrapper);
}

@Test
public void testWrapper8() {
QueryWrapper wrapper = new QueryWrapper<>();
wrapper.eq("user_name", "bbb");
userMapper.delete(wrapper);
}

@Test
public void testWrapper9() {
UpdateWrapper wrapper = new UpdateWrapper<>();
//条件
wrapper.eq("user_name", "lisi")
.set("password", "22222");
//update tb_user set password = ? where user_name = ?
userMapper.update(null, wrapper);
}
@Test
public void testWrapper10() {
UpdateWrapper wrapper = new UpdateWrapper<>();
//条件
wrapper.eq("user_name", "lisi");
//update tb_user set password = ?,age = ? where user_name = ?
User user = new User();
user.setPassword("3333");
user.setAge(33);
userMapper.update(user, wrapper);
  }
}

mp实现的修改只是将指定的字段做了修改,原来没有指定的字段还是原来数据,并不是null 

 需要注意的是修改条件构造器和lam格式的条件构造器,大致上增删改查就这样完成了!!!

方式一:

在mapper中添加自己的方法即可:

示例:

public interface UserMapper extends baseMapper {
    
    @Select("select name, age from tb1,tb2 where id=1")
    public User selectManyTable();
}

方式二:

持久层进行单表查询,业务层实现pojo的数据重组

plication.properties # datasource spring.datasource.url = jdbc:mysql://47.119.137.8:3306/mytest spring.datasource.password = root spring.datasource.username = root spring.datasource.driver-class-name = com.mysql.jdbc.Driver # myatisplus 配置 # 表前缀,根据情况填写 #mybatis-plus.global-config.db-config.table-prefix= # id 策略 mybatis-plus.global-config.db-config.id-type = auto # 日志,查看生成的 sql 语句 mybatis-plus.configuration.log-impl = org.apache.ibatis.logging.stdout.StdOutImpl # 枚举包的扫描(该枚举完成对一些不变数据的赋值) mybatis-plus.type-enums-package = com.nanfeng.nan.mybatisplus.enums

使用mp注意事项: