一、mapper接口中的方法解析
mapper接口中的函数及方法
二、example实例解析
mybatis的逆向工程中会生成实例及实例对应的example,example用于添加条件,相当where后面的部分
xxxExample example = new xxxExample();
Criteria criteria = new Example().createCriteria();
三、应用举例
1.查询
① selectByPrimaryKey()
1 User user = XxxMapper.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("wyw"); criteria.andUsernameIsNull(); example.setOrderByClause("username asc,email desc"); List>list = XxxMapper.selectByExample(example); //相当于:select * from user where username = 'wyw' and username is null order by username asc,email desc
注:在iBator逆向工程生成的文件XxxExample.java中包含一个static的内部类Criteria,Criteria中的方法是定义SQL 语句where后的查询条件。
2.插入数据
①insert()
User user = new User(); user.setId("dsfgsdfgdsfgds"); user.setUsername("admin"); user.setPassword("admin") user.setEmail("[email protected]"); XxxMapper.insert(user); //相当于:insert into user(ID,username,password,email) values ('dsfgsdfgdsfgds','admin','admin','[email protected]');
3.更新数据
①updateByPrimaryKey()
User user =new User(); user.setId("dsfgsdfgdsfgds"); user.setUsername("wyw"); user.setPassword("wyw"); user.setEmail("[email protected]"); XxxMapper.updateByPrimaryKey(user); //相当于: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); //相当于: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); //相当于:update user set password='wyw' where username='admin'
updateByExample()更新所有的字段,包括字段为null的也更新,建议使用 updateByExampleSelective()更新想更新的字段
4.删除数据
①deleteByPrimaryKey()
XxxMapper.deleteByPrimaryKey(1); //相当于:delete from user where id=1
②deleteByExample()
UserExample example = new UserExample(); Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("admin"); XxxMapper.deleteByExample(example); //相当于:delete from user where username='admin'
5.查询数据数量
①countByExample()
UserExample example = new UserExample(); Criteria criteria = example.createCriteria(); criteria.andUsernameEqualTo("wyw"); int count = XxxMapper.countByExample(example); //相当于:select count(*) from user where username='wyw'