[Java知识库]（三）基础知识-3：关于Mapper，LambdaQueryWrapper，MyBatis-Plus

目录

1-Mapper：

1.1-**Mapper.java

1.2-**Mapper.xml

2- LambdaQueryWrapper+MyBatis-Plus

小记：

查询user_name==’rushi’, role_state==3的数据。

1-Mapper：

小记：

如果有分表的库表，使用Mapper实现增删改查较方便些。

1.1-**Mapper.java

List<UserBlogDTO>?getUserByNameState(@Param("userName")?String?userName,?@Param("roleState")?Integer?roleState);

1.2-**Mapper.xml

?????<select?id="getUserByNameState"?resultType="org.lcy.com.data.entity.BlogUsers">
?????????select?id,?user_name,?nick_name
?????????from?blog_users
?????????where?user_id=#{userId}?and?role_state=#{roleState}
?????</select>

2- LambdaQueryWrapper+MyBatis-Plus

public?List<BlogUsersDTO>?getUserByNameState(String?userName,?Integer?roleState)?{
????????LambdaQueryWrapper<BlogUsers>?queryWrapper?=?new?LambdaQueryWrapper<>();
????????queryWrapper.eq(BlogUsers::getUserName,?userName);
????????queryWrapper.eq(BlogUsers::getRoleState,?roleState);
????????queryWrapper.select(BlogUsers::getId,?BlogUsers::getUserName,BlogUsers::getNickName);

????????List<BlogUsers>?blogUsers?=?list(queryWrapper);

????????return?blogUsers.stream().map(BlogUsersConverter::convertToDTO).collect(Collectors.toList());
????}

--------------------
作者：Username1898625
创作不易，转载已注明出处
--------------------