mybatis中的mapper接口文件以及example类的实例函数以及详解

Posted 2020-10-03

##Example example = new ##Example();    
example.setOrderByClause("字段名 ASC"); //升序排列，desc为降序排列。    
example.setDistinct(false)//去除重复，boolean型，true为选择不重复的记录。    
Criteria criteria = new Example().createCriteria();    
is null;is not null;    
equal to(value);not equal to(value);    
GreaterThan(value);GreaterThanOrEqualTo(value);    
LessThan(value); LessThanOrEqualTo(value);    
in(item,item,item,...);not in(item,item,item,...);    
like("%"+value+"%");not like("%"+value+"%");    
Between(value1,value2);not between(value1,value2)        
mybatis中mapper的实例函数:    
int countByExample(UserExample example) thorws SQLException：按条件计数。    
int deleteByPrimaryKey(Integer id) thorws SQLException：按主键删除。    
int deleteByExample(UserExample example) thorws SQLException：按条件删除。    
String/Integer insert(User record) thorws SQLException：插入(返回值为id值)    
User selectByPrimaryKey(Integer id) thorws SQLException：按主键查询。    
List<?>selectByExample(UserExample example) thorws SQLException：按条件查询    
List<?>selectByExampleWithBLOGs(UserExample example) thorws SQLException：按    
    
条件查询（包括BLOB字段）。只有当数据表中的字段类型有为二进制的才会产生。    
int updateByPrimaryKey(User record) thorws SQLException：按主键更新    
int updateByPrimaryKeySelective(User record) thorws SQLException：按主键更新    
    
 值不为null的字段    
int updateByExample(User record, UserExample example) thorws SQLException：     
按条件更新    
int updateByExampleSelective(User record, UserExample example) thorws          
SQLException：按条件更新值不为null的字段        
mybatis中mapper的实例函数详解：    
① selectByPrimaryKey()        
User user = ##Mapper.selectByPrimaryKey(100); 相当于select * from user where      
id = 100        
② selectByExample() 和 selectByExampleWithBLOGs()        
UserExample example = new UserExample();    
Criteria criteria = example.createCriteria();    
criteria.andUsernameEqualTo("joe");    
criteria.andUsernameIsNull();    
example.setOrderByClause("username asc,email desc");    
List<?>list = ##Mapper.selectByExample(example);    
相当于：select * from user where username = ‘joe‘ and username is null order        
by username asc,email desc        
注：在iBator 生成的文件UserExample.java中包含一个static 的内部类 Criteria ，       
在Criteria中有很多方法，主要是定义SQL 语句where后的查询条件。        
③ insert()       
User user = new User();    
user.setId(101);    
user.setUsername("test");    
user.setPassword("123")    
user.setEmail("[email protected]");    
##Mapper.insert(user);    
相当于：insert into user(ID,username,password,email) values        
(101,‘test‘,‘123‘,‘[email protected]‘);        
 ④ updateByPrimaryKey() 和 updateByPrimaryKeySelective()        
User user =new User();    
user.setId(101);    
user.setUsername("joe");    
user.setPassword("joe");    
user.setEmail("[email protected]");    
##Mapper.updateByPrimaryKey(user);    
相当于：update user set username=‘joe‘,password=‘joe‘,email=‘[email protected]‘        
where id=101       
User user = new User();    
user.setId(101);    
user.setPassword("joe");    
##Mapper.updateByPrimaryKeySelective(user);    
相当于：update user set password=‘joe‘ where id=101        
⑤ updateByExample() 和 updateByExampleSelective()        
UserExample example = new UserExample();    
Criteria criteria = example.createCriteria();    
criteria.andUsernameEqualTo("joe");    
User user = new User();    
user.setPassword("123");    
##Mapper.updateByPrimaryKeySelective(user,example);    
相当于：update user set password=‘123‘ where username=‘joe‘       
⑥ deleteByPrimaryKey()       
##Mapper.deleteByPrimaryKey(101);  相当于：delete from user where id=101       
⑦ deleteByExample()       
UserExample example = new UserExample();    
Criteria criteria = example.createCriteria();    
criteria.andUsernameEqualTo("joe");    
##Mapper.deleteByExample(example);    
相当于：delete from user where username=‘joe‘        
⑧ countByExample()        
UserExample example = new UserExample();    
Criteria criteria = example.createCriteria();    
criteria.andUsernameEqualTo("joe");    
int count = ##Mapper.countByExample(example);    
相当于：select count(*) from user where username=‘joe‘