MybatisPlus Conditional constructor

This is the 11th day of my participation in the Gwen Challenge in November. Check out the details: The last Gwen Challenge in 2021

Conditional constructor

Conditional constructors are used to write complex SQL

Matters needing attention

Transmission of Wrapper in RPC calls is not supported or approved

1. wrapperVery heavy
2. transmissionwrapperCan be compared to yourscontroller 用 mapReceived value (develop instant gratification, maintain crematorium)
3. The correctRPCCall posture is write oneDTOTransfer, the called party according toDTOPerform the corresponding operations

Stitching method

isNotnullandgedemo

@Test  
void test1(a) {  
 // Query name is not empty and mailbox is not empty, age is greater than 15
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.  
            isNotNull("name").  
            isNotNull("email").  
            ge("age".15);  
    userMapper.selectList(wrapper).forEach(System.out::println);  
}
Copy the code

eqandselectOnedemo

@Test  
void test2(a) {  
 / / query name = test2
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.eq("name"."test2");  
    //selectOne can query only one selectOne
 User user = userMapper.selectOne(wrapper);  
    System.out.println(user);  
}
Copy the code

betweenandselectCountdemo

@Test  
void test3(a) {  
 // query the user whose age is between [20,30]
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.between("age".20.30);  
    long count = userMapper.selectCount(wrapper);  
    System.out.println(count);  
}
Copy the code

notLikeandlikeRightandselectMapsdemo

@Test  
void test4(a) {  
 //name does not contain BC and email starts with t (t%)
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.  
            notLike("name"."bc").  
            likeRight("email"."t");  
    List<Map<String, Object>> maps = userMapper.selectMaps(wrapper);  
    maps.forEach(System.out::println);  
}
Copy the code

inSqlandselectObjsAnd subquery demo

@Test  
void test5(a) {  
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.inSql("id"."SELECT id FROM user WHERE id < 10");  
    List<Object> objects = userMapper.selectObjs(wrapper);  
    objects.forEach(System.out::println);  
}
Copy the code

orderByDescdemo

@Test  
void test6(a) {  
 QueryWrapper<User> wrapper = new QueryWrapper<>();  
    wrapper.orderByDesc("id");  
    List<User> users = userMapper.selectList(wrapper);  
    users.forEach(System.out::println);  
}
Copy the code