一、mapper介面中的方法解析 mapper介面中的函數及方法
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 |
插入資料(傳回值為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欄位)。只有當資料表中的欄位類型有為二進位的才會產生。 |
int updateByPrimaryKey(User record) thorws SQLException |
按主鍵更新 |
int updateByPrimaryKeySelective(User record) thorws SQLException |
按主鍵更新值不為null的欄位 |
int updateByExample(User record, UserExample example) thorws SQLException |
按條件更新 |
int updateByExampleSelective(User record, UserExample example) thorws SQLException |
按條件更新值不為null的欄位 |
二、example執行個體解析mybatis的逆向工程中會產生執行個體及執行個體對應的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(“欄位名 ASC”); |
添加升序排列條件,DESC為降序 |
example.setDistinct(false) |
去除重複,boolean型,true為選擇不重複的記錄。 |
criteria.andXxxIsNull |
添加欄位xxx為null的條件 |
criteria.andXxxIsNotNull |
添加欄位xxx不為null的條件 |
criteria.andXxxEqualTo(value) |
添加xxx欄位等於value條件 |
criteria.andXxxNotEqualTo(value) |
添加xxx欄位不等於value條件 |
criteria.andXxxGreaterThan(value) |
添加xxx欄位大於value條件 |
criteria.andXxxGreaterThanOrEqualTo(value) |
添加xxx欄位大於等於value條件 |
criteria.andXxxLessThan(value) |
添加xxx欄位小於value條件 |
criteria.andXxxLessThanOrEqualTo(value) |
添加xxx欄位小於等於value條件 |
criteria.andXxxIn(List<?>) |
添加xxx欄位值在List<?>條件 |
criteria.andXxxNotIn(List<?>) |
添加xxx欄位值不在List<?>條件 |
criteria.andXxxLike(“%”+value+”%”) |
添加xxx欄位值為value的模糊查詢條件 |
criteria.andXxxNotLike(“%”+value+”%”) |
添加xxx欄位值不為value的模糊查詢條件 |
criteria.andXxxBetween(value1,value2) |
添加xxx欄位值在value1和value2之間條件 |
criteria.andXxxNotBetween(value1,value2) |
添加xxx欄位值不在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 = 100
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 desc
註:在iBator逆向工程產生的檔案XxxExample.Java中包含一個static的內部類Criteria,Criteria中的方法是定義SQL 陳述式where後的查詢條件。 2.插入資料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]‘);
3.更新資料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‘
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‘
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‘
updateByExample()更新所有的欄位,包括欄位為null的也更新,建議使用 updateByExampleSelective()更新想更新的欄位 4.刪除資料①deleteByPrimaryKey() XxxMapper.deleteByPrimaryKey(1); //相當於:delete from user where id=1
②deleteByExample() UserExample example = new UserExample();Criteria criteria = example.createCriteria();criteria.andUsernameEqualTo("admin");XxxMapper.deleteByExample(example);//相當於:delete from user where username=‘admin‘
5.查詢資料數量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‘
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