关于通用Mapper问题

简单记录，避免再犯

1.通用mapper按条件查询

Example example = new Example(Users.class);
Example.Criteria criteria = example.createCriteria();
criteria.andEqualTo("username", username);

// 错误，会抛异常
// Users users = usersMapper.selectOneByExample(criteria);

// 正确。这里应该放 Example 而不应该放Criteria
Users users = usersMapper.selectOneByExample(criteria);