通用mapper 根据条件修改、查询 Example的实例函数及例子

**

通用mapper 根据条件修改、查询 Example的实例函数及例子

**
条件：
Example example = new Example(User.class);
Criteria criteria = example.createCriteria();

注意：
criteria.andEqualTo(property, value)；
property 对应的是实体类中的属性字段
1、根据条件查询

    /**
     * 根据名称，id,ntype等获取其对应节点总数
     * 用于判断名称是否重复
     */
    public int getCountByNameAndUId(String name, Long id, Long userId) {

        Example example = new Example(User.class);
        Criteria criteria = example.createCriteria();


        criteria.andEqualTo("name", name);
        criteria.andNotEqualTo("id", id);
        criteria.andEqualTo("userId", uid);

        int count = categoryMapper.selectCountByExample(example);

        return count;
    }

等效于：
Select count(0) from user where name = #{name} and id != #{id} and uid != #{uid}

2、and or 查询

public Example test(List ids, String name, String des) {
Example example = new Example(User.getClass());
        // where 条件
        Criteria criteria = example.createCriteria();
        Criteria criteria1 = example.createCriteria();


        criteria.andIn("id", ids);
        criteria1.orLike("des", "%" + des + "%");
        criteria1.orLike("name", "%" + name + "%");
        example.and(criteria1);

       return example;
}

等效于：
 where id in ( #{ids} ) and ( name like concat(‘%’, #{name} ,’%’) or des like concat(‘%’, #{des} ,’%’) )

3、根据条件修改

    Example example = new Example(User.getClass());
        // where 条件
        Criteria criteria = example.createCriteria();
        criteria.andEqualTo("name", name);
        userMapper.updateByExampleSelective(user, example);
等效于：
Update user set ... where name = #{name}

参照：
MyBatis的Mapper接口以及Example的实例函数及详解(http://blog.csdn.net/biandous/article/details/65630783)
通用mapper