mybatis中Mapper接口文件以及Example类实例解析

创建Condition类继承Example类：

public class Condition extends Example {
    public Condition(Class<?> entityClass) {
        super(entityClass);
    }

    public Condition(Class<?> entityClass, boolean exists) {
        super(entityClass, exists);
    }

    public Condition(Class<?> entityClass, boolean exists, boolean notNull) {
        super(entityClass, exists, notNull);
    }
}

在controller中调用Condition类：

@PostMapping("/kjlist")
    public Result kjlist() {
        Condition condition = new Condition(Zwsx.class);
        Condition.Criteria criteria = condition.createCriteria();   //創建實例
        criteria.andEqualTo("type","1").andEqualTo("flag", "1").andEqualTo("xsbz","1");
        condition.setOrderByClause("seq");  //將seq字段升序排列
        //相當於：select * from tb_zwsx where type = '1' and flag = '1' and xsbz = '1' order by seq asc
        //從tb_zwsx表查詢出快捷事項的四個結果：新生重名查詢、身份證進度辦理查詢、單位/從業人員、房屋/居住人員
        List<Zwsx> list = zwsxService.findByCondition(condition);
        return ResultGenerator.genSuccessResult(list);
    }

下列是Example类：

	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'