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

 使用Example 过程。

github ：https://github.com/foolchild/ibatis-example

1.添加依赖

<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper-spring-boot-starter</artifactId>
    <version>2.1.5</version>
</dependency>


2.解决mapper.xml文件不能随便放的问题。
1.添加build 属性

<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
            <filtering>false</filtering>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
        </resource>
    </resources>
</build>
2.添加配置properties

mybatis.mapper-locations=classpath*:com/test/test/mapper/*.xml

3.启动类添加配置

@MapperScan("com.ibatis.example.mapper")

##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("joe@163.com");  

##Mapper.insert(user);  

相当于：insert into user(ID,username,password,email) values  (101,'test','123','joe@163.com');  

 ④ updateByPrimaryKey() 和 updateByPrimaryKeySelective()  

User user =new User();  

user.setId(101);  

user.setUsername("joe");  

user.setPassword("joe");  

user.setEmail("joe@163.com");  

##Mapper.updateByPrimaryKey(user);  

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