今天完成的事情：

今天主要解决多表查询问题，更准确的是一对一的查询

这是完成的Controller 但是用不了插件排序…………

@Autowired
StudyCollectionServer studyCollectionServer;

/**
 * 收藏列表查询
 * 查找当前用户收藏等于对应类型的所有学习对象
 * @param type 学习对象类型
 */
@GetMapping("/a/u/list/collection")
public Map<String, Object> collectionListSelect(Long id,Integer type,
                                                @RequestParam(value = "page", defaultValue = "1") Integer page,
                                                @RequestParam(value = "size", defaultValue = "10") Integer size) {
    log.info("获取第{}页共{}行{}类型的收藏学习对象信息", page, size, type);
    HashMap<String, Object> result = new HashMap<>(16);

    StudyCollection studyCollection = new StudyCollection();
    studyCollection.setCreateBy(id);

    StudyObject studyObject = new StudyObject();
    studyObject.setType(type);
    studyCollection.setStudyObject(studyObject);
    PageHelper.startPage(page,size);
    List studyCollectionList=studyCollectionServer.selectUserStudyCollection(studyCollection);
    PageInfo pageInfo=new PageInfo<>(studyCollectionList);
    Long total = pageInfo.getTotal();
    result.put("code", SUCCESS.getCode());
    result.put("msg", SUCCESS.getMsg());
    result.put("total", total);
    result.put("data", studyCollectionList);
    return result;
}

要弄mybatis的一对一查询，要三步

从表实体类要导入主表的类。生成get和set

private StudyObject studyObject;

public StudyObject getStudyObject() {
    return studyObject;
}

public void setStudyObject(StudyObject studyObject) {
    this.studyObject = studyObject;
}

在从表的mapper.xml里用association添加主表的返回类型。

<resultMap id="BaseResultMap" type="com.happynewyear.user.pojo.StudyCollection">
  <id column="id" jdbcType="BIGINT" property="id" />
  <result column="study_object_id" jdbcType="BIGINT" property="studyObjectId" />
  <result column="create_at" jdbcType="BIGINT" property="createAt" />
  <result column="update_at" jdbcType="BIGINT" property="updateAt" />
  <result column="create_by" jdbcType="BIGINT" property="createBy" />
  <result column="update_by" jdbcType="BIGINT" property="updateBy" />
  <association property="studyObject" column="id" javaType="com.happynewyear.user.pojo.StudyObject">
    <result property="id" column="id"/>
    <result property="title" column="title"/>
    <result property="type" column="type"/>
    <result property="cover" column="cover"/>
    <result property="price" column="price"/>
    <result property="discount" column="discount"/>
    <result property="content" column="content"/>
  </association>
</resultMap>

使用的SQL语句。

<select id="selectUserStudyCollection" resultMap="BaseResultMap">
  SELECT c.study_object_id ,o.title,c.id
  FROM
  study_collection as c,study_object as o
  WHERE
  c.study_object_id=o.id  AND c.create_by=#{createBy}
</select>

只能做到这步了。

明天计划的事情：

把收藏接口写完。把排序加上弄的出来的话

遇到的问题：

虽然做出来了，但是还不是太理解

收获：

mybatis一对一查询