MyBatis通用Mapper接口Example的实例

⼀、mapper接⼝中的⽅法解析

mapper接⼝中的函数及⽅法

⽅法

int countByExample(UserExample example) thorws SQLExceptionint deleteByPrimaryKey(Integer id) thorws SQLException

int deleteByExample(UserExample example) thorws SQLExceptionString/Integer insert(User record) thorws SQLExceptionUser selectByPrimaryKey(Integer id) thorws SQLExceptionListselectByExample(UserExample example) thorws SQLExceptionListselectByExampleWithBLOGs(UserExample example) thorwsSQLException

int updateByPrimaryKey(User record) thorws SQLExceptionint updateByExample(User record, UserExample example) thorwsSQLException

int updateByExampleSelective(User record, UserExample example)thorws SQLException

按条件计数按主键删除按条件查询

插⼊数据（返回值为ID）按主键查询按条件查询

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。按主键更新

功能说明

int updateByPrimaryKeySelective(User record) thorws SQLException按主键更新值不为null的字段

按条件更新

按条件更新值不为null的字段

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();

⽅法

example.setOrderByClause(“字段名 ASC”);example.setDistinct(false)criteria.andXxxIsNullcriteria.andXxxIsNotNullcriteria.andXxxEqualTo(value)criteria.andXxxNotEqualTo(value)criteria.andXxxGreaterThan(value)criteria.andXxxLessThan(value)

criteria.andXxxLessThanOrEqualTo(value)criteria.andXxxIn(List<？>)criteria.andXxxNotIn(List<？>)criteria.andXxxLike(“%”+value+”%”)criteria.andXxxNotLike(“%”+value+”%”)criteria.andXxxBetween(value1,value2)criteria.andXxxNotBetween(value1,value2)

说明

添加升序排列条件，DESC为降序

去除重复，boolean型，true为选择不重复的记录。添加字段xxx为null的条件添加字段xxx不为null的条件添加xxx字段等于value条件添加xxx字段不等于value条件添加xxx字段⼤于value条件添加xxx字段⼩于value条件添加xxx字段⼩于等于value条件添加xxx字段值在List<？>条件添加xxx字段值不在List<？>条件添加xxx字段值为value的模糊查询条件添加xxx字段值不为value的模糊查询条件添加xxx字段值在value1和value2之间条件添加xxx字段值不在value1和value2之间条件

criteria.andXxxGreaterThanOrEqualTo(value)添加xxx字段⼤于等于value条件

三、应⽤举例

1.查询

① selectByPrimaryKey()

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\");Listlist = 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(\"wyw@163.com\");XxxMapper.insert(user);

//相当于：insert into user(ID,username,password,email) values ('dsfgsdfgdsfgds','admin','admin','wyw@126.com');

3.更新数据

①updateByPrimaryKey()

User user =new User();

user.setId(\"dsfgsdfgdsfgds\");user.setUsername(\"wyw\");user.setPassword(\"wyw\");

user.setEmail(\"wyw@163.com\");

XxxMapper.updateByPrimaryKey(user);

//相当于：update user set username='wyw', password='wyw', email='wyw@163.com' 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'