mybatis的Mapper接口以及Example的實例函數與SQL語句對應關係詳解
一、mapper接口中的方法解析
mapper接口中的函數及方法
方法 | 功能說明 |
---|---|
int countByExample(UserExample example) thorws SQLException | 按條件計數 |
int deleteByPrimaryKey(Integer id) thorws SQLException | 按主鍵刪除 |
int deleteByExample(UserExample example) thorws SQLException | 按條件查詢 |
String/Integer insert(User record) thorws SQLException | 插入數據(返回值爲ID) |
User selectByPrimaryKey(Integer id) thorws SQLException | 按主鍵查詢 |
ListselectByExample(UserExample example) thorws SQLException | 按條件查詢 |
ListselectByExampleWithBLOGs(UserExample example) thorws SQLException | 按條件查詢(包括BLOB字段)。只有當數據表中的字段類型有爲二進制的纔會產生。 |
int updateByPrimaryKey(User record) thorws SQLException | 按主鍵更新 |
int updateByPrimaryKeySelective(User record) thorws SQLException | 按主鍵更新值不爲null的字段 |
int updateByExample(User record, UserExample example) thorws SQLException | 按條件更新 |
int updateByExampleSelective(User record, UserExample example) thorws SQLException | 按條件更新值不爲null的字段 |
二、example實例解析
mybatis的逆向工程中會生成實例及實例對應的example,example用於添加條件,相當where後面的部分
xxxExample example = new xxxExample();
Criteria criteria = new Example().createCriteria();
方法 | 說明 |
---|---|
example.setOrderByClause(“字段名 ASC”); | 添加升序排列條件,DESC爲降序 |
example.setDistinct(false) | 去除重複,boolean型,true爲選擇不重複的記錄。 |
criteria.andXxxIsNull | 添加字段xxx爲null的條件 |
criteria.andXxxIsNotNull | 添加字段xxx不爲null的條件 |
criteria.andXxxEqualTo(value) | 添加xxx字段等於value條件 |
criteria.andXxxNotEqualTo(value) | 添加xxx字段不等於value條件 |
criteria.andXxxGreaterThan(value) | 添加xxx字段大於value條件 |
criteria.andXxxGreaterThanOrEqualTo(value) | 添加xxx字段大於等於value條件 |
criteria.andXxxLessThan(value) | 添加xxx字段小於value條件 |
criteria.andXxxLessThanOrEqualTo(value) | 添加xxx字段小於等於value條件 |
criteria.andXxxIn(List<?>) | 添加xxx字段值在List<?>條件 |
criteria.andXxxNotIn(List<?>) | 添加xxx字段值不在List<?>條件 |
criteria.andXxxLike(“%”+value+”%”) | 添加xxx字段值爲value的模糊查詢條件 |
criteria.andXxxNotLike(“%”+value+”%”) | 添加xxx字段值不爲value的模糊查詢條件 |
criteria.andXxxBetween(value1,value2) | 添加xxx字段值在value1和value2之間條件 |
criteria.andXxxNotBetween(value1,value2) | 添加xxx字段值不在value1和value2之間條件 |
三、應用舉例
1.查詢
① selectByPrimaryKey()
User user = XxxMapper.selectByPrimaryKey(100); //相當於select * from user where id = 1001
② selectByExample() 和 selectByExampleWithBLOGs()
UserExample example = new UserExample();
Criteria criteria = example.createCriteria();
criteria.andUsernameEqualTo("wyw");
criteria.andUsernameIsNull();
example.setOrderByClause("username asc,email desc");
List<?>list = XxxMapper.selectByExample(example);
//相當於:select * from user where username = 'wyw' and username is null order by username asc,email desc1234567
注:在iBator逆向工程生成的文件XxxExample.java中包含一個static的內部類Criteria,Criteria中的方法是定義SQL 語句where後的查詢條件。
2.插入數據
①insert()
User user = new User();
user.setId("dsfgsdfgdsfgds");
user.setUsername("admin");
user.setPassword("admin")
user.setEmail("[email protected]");
XxxMapper.insert(user);
//相當於:insert into user(ID,username,password,email) values ('dsfgsdfgdsfgds','admin','admin','[email protected]');1234567
3.更新數據
①updateByPrimaryKey()
User user =new User();
user.setId("dsfgsdfgdsfgds");
user.setUsername("wyw");
user.setPassword("wyw");
user.setEmail("[email protected]");
XxxMapper.updateByPrimaryKey(user);
//相當於:update user set username='wyw', password='wyw', email='[email protected]' where id='dsfgsdfgdsfgds'1234567
②updateByPrimaryKeySelective()
User user = new User();
user.setId("dsfgsdfgdsfgds");
user.setPassword("wyw");
XxxMapper.updateByPrimaryKey(user);
//相當於:update user set password='wyw' where id='dsfgsdfgdsfgds'12345
③ updateByExample() 和 updateByExampleSelective()
UserExample example = new UserExample();
Criteria criteria = example.createCriteria();
criteria.andUsernameEqualTo("admin");
User user = new User();
user.setPassword("wyw");
XxxMapper.updateByPrimaryKeySelective(user,example);
//相當於:update user set password='wyw' where username='admin'1234567
updateByExample()更新所有的字段,包括字段爲null的也更新,建議使用 updateByExampleSelective()更新想更新的字段
4.刪除數據
①deleteByPrimaryKey()
XxxMapper.deleteByPrimaryKey(1); //相當於:delete from user where id=11
②deleteByExample()
UserExample example = new UserExample();
Criteria criteria = example.createCriteria();
criteria.andUsernameEqualTo("admin");
XxxMapper.deleteByExample(example);
//相當於:delete from user where username='admin'12345
5.查詢數據數量
①countByExample()
UserExample example = new UserExample();
Criteria criteria = example.createCriteria();
criteria.andUsernameEqualTo("wyw");
int count = XxxMapper.countByExample(example);
//相當於:select count(*) from user where username='wyw'