类似于：select * from user where name={#user.name} and sex={#user.sex} order by age asc;
UserExample example = new UserExample();
UserExample.Criteria criteria1 = example.createCriteria();
UserExample.Criteria criteria2 = example.createCriteria();
if(!StringUtils.isNotBlank(user.getName())){
Criteria1.andNameEqualTo(user.getName());
}
if(!StringUtils.isNotBlank(user.getSex())){
Criteria2.andSexEqualTo(user.getSex());
}
Example.or(criteria2);
List<User> userList=userMapper.selectByExample(example);
example.setOrderByClause(“age asc"); //升序
example.setDistinct(false); //不去重
