mybatis逆向工程之生成文件解释

矫情吗；* 2022-05-14 01:49 210阅读 0赞

### 一、mapper接口中的方法解析 ###

mapper接口中的函数及方法

<table> 
 <thead> 
  <tr> 
   <th>方法</th> 
   <th>功能说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>int countByExample(UserExample example) thorws SQLException</td> 
   <td>按条件计数</td> 
  </tr> 
  <tr> 
   <td>int deleteByPrimaryKey(Integer id) thorws SQLException</td> 
   <td>按主键删除</td> 
  </tr> 
  <tr> 
   <td>int deleteByExample(UserExample example) thorws SQLException</td> 
   <td>按条件查询</td> 
  </tr> 
  <tr> 
   <td>String/Integer insert(User record) thorws SQLException</td> 
   <td>插入数据（返回值为ID）</td> 
  </tr> 
  <tr> 
   <td>User selectByPrimaryKey(Integer id) thorws SQLException</td> 
   <td>按主键查询</td> 
  </tr> 
  <tr> 
   <td>ListselectByExample(UserExample example) thorws SQLException</td> 
   <td>按条件查询</td> 
  </tr> 
  <tr> 
   <td>ListselectByExampleWithBLOGs(UserExample example) thorws SQLException</td> 
   <td>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。</td> 
  </tr> 
  <tr> 
   <td>int updateByPrimaryKey(User record) thorws SQLException</td> 
   <td>按主键更新</td> 
  </tr> 
  <tr> 
   <td>int updateByPrimaryKeySelective(User record) thorws SQLException</td> 
   <td>按主键更新值不为null的字段</td> 
  </tr> 
  <tr> 
   <td>int updateByExample(User record, UserExample example) thorws SQLException</td> 
   <td>按条件更新</td> 
  </tr> 
  <tr> 
   <td>int updateByExampleSelective(User record, UserExample example) thorws SQLException</td> 
   <td>按条件更新值不为null的字段</td> 
  </tr> 
 </tbody> 
</table>

### 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();

<table> 
 <thead> 
  <tr> 
   <th>方法</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>example.setOrderByClause(“字段名 ASC”);</td> 
   <td>添加升序排列条件，DESC为降序</td> 
  </tr> 
  <tr> 
   <td>example.setDistinct(false)</td> 
   <td>去除重复，boolean型，true为选择不重复的记录。</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxIsNull</td> 
   <td>添加字段xxx为null的条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxIsNotNull</td> 
   <td>添加字段xxx不为null的条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxEqualTo(value)</td> 
   <td>添加xxx字段等于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxNotEqualTo(value)</td> 
   <td>添加xxx字段不等于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxGreaterThan(value)</td> 
   <td>添加xxx字段大于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxGreaterThanOrEqualTo(value)</td> 
   <td>添加xxx字段大于等于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxLessThan(value)</td> 
   <td>添加xxx字段小于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxLessThanOrEqualTo(value)</td> 
   <td>添加xxx字段小于等于value条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxIn(List&lt;？&gt;)</td> 
   <td>添加xxx字段值在List&lt;？&gt;条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxNotIn(List&lt;？&gt;)</td> 
   <td>添加xxx字段值不在List&lt;？&gt;条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxLike(“%”+value+”%”)</td> 
   <td>添加xxx字段值为value的模糊查询条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxNotLike(“%”+value+”%”)</td> 
   <td>添加xxx字段值不为value的模糊查询条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxBetween(value1,value2)</td> 
   <td>添加xxx字段值在value1和value2之间条件</td> 
  </tr> 
  <tr> 
   <td>criteria.andXxxNotBetween(value1,value2)</td> 
   <td>添加xxx字段值不在value1和value2之间条件</td> 
  </tr> 
 </tbody> 
</table>

### 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");
    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("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'

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'

[Java]: http://lib.csdn.net/base/java