Java-Tree多种操作(递归)

Mybatis 直接返回tree结构

实体类环境搭建

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@Data
public class MyCloudDisk implements Serializable {
    /**
     * ID
     */
    private String id;

    /**
     * 名称
     */
    private String name;

    /**
     * 上级父ID
     */
    private String pid;
}
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@Data
public class MyCloudDiskTypeCustom extends MyCloudDisk {

    private Integer depth;
    private List<MyCloudDiskTypeCustom> children;
}

获取数据

**注意：要两个select标签都是这一个resultmap，第一个是查找根节点，第二个是递归查找节点 **

通过传入根节点的id查询下属子节点

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 <!-- start 根据子id查父类文件夹 -->
    <select id="selectByPid" resultMap="recursionFolderTypeMap">
         SELECT * FROM my_cloud_disk
         WHERE   pid = #{id} 
</select>

    <!-- start 根据子id查子类文件夹 -->
    <select id="findFolderByParentId" resultMap="recursionFolderTypeMap">
    SELECT * FROM my_cloud_disk WHERE pid = #{id}
</select>


    <resultMap id="recursionFolderTypeMap" type="MyCloudDiskTypeCustom">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="pid" jdbcType="VARCHAR" property="pid" />
        <collection property="children" ofType="MyCloudDiskTypeCustom"
                    column="id" select="findFolderByParentId">
        </collection>
    </resultMap>

通过传入子节点的id查询上级父类节点

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 <!-- start 根据子id查子类文件夹 -->
    <select id="findAllRecursion" resultMap="recursionNewsTypeMap">
         SELECT * FROM my_cloud_disk
         WHERE   id = #{id}
        ORDER BY `CREATE_TIME_` desc
</select>
    <!-- start 根据子id查父类文件夹 -->
    <select id="findNewsByParentId" resultMap="recursionNewsTypeMap">
    SELECT * FROM my_cloud_disk WHERE id = #{pid} ORDER BY `CREATE_TIME_` desc
</select>

    <resultMap id="recursionNewsTypeMap" type="MyCloudDiskTypeCustom">
        <id column="id" jdbcType="VARCHAR" property="id" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="pid" jdbcType="VARCHAR" property="pid" />
        <collection property="children" ofType="MyCloudDiskTypeCustom"
                    column="pid" select="findNewsByParentId">
        </collection>
    </resultMap>

Java

tree转list

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/**
    * tree转list
    * @param messageList
    * @return
    */
   private List<MyCloudDiskTypeCustom> treeToList(List<MyCloudDiskTypeCustom> messageList) {
       List<MyCloudDiskTypeCustom> result = new ArrayList<>();
       for (MyCloudDiskTypeCustom entity : messageList) {
           result.add(entity);
           List<MyCloudDiskTypeCustom> childMsg = entity.getChildren();
           if (childMsg != null && childMsg.size() > 0) {
               List<MyCloudDiskTypeCustom> entityList = this.treeToList(childMsg);
               result.addAll(entityList);
           }
       }
       if (result.size() > 0) {
           for (MyCloudDiskTypeCustom entity : result) {
               entity.setChildren(null);
           }
       }
       return result;
   }

list 转 tree

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/**
 * list 转 tree
 * @param msgEntity
 * @param allList
 * @return
 */
private List<MyCloudDiskTypeCustom> messageListToTree(MyCloudDiskTypeCustom msgEntity, List<MyCloudDiskTypeCustom> allList) {
    List<MyCloudDiskTypeCustom> msgList = new ArrayList<>();
    for (MyCloudDiskTypeCustom messageEntity : allList) {
        if (messageEntity.getPid().equals(msgEntity.getId())) {
            if (msgEntity.getChildren() == null) {
                msgEntity.setChildren(new ArrayList<>());
            }
            msgEntity.getChildren().add(findChild(messageEntity, allList));
        }
    }
    msgList.add(msgEntity);
    return msgList;
}
private MyCloudDiskTypeCustom findChild(MyCloudDiskTypeCustom messageEntity, List<MyCloudDiskTypeCustom> allList) {
    for (MyCloudDiskTypeCustom entity : allList) {
        if (entity.getPid().equals(messageEntity.getId())) {
            if (messageEntity.getChildren() == null) {
                messageEntity.setChildren(new ArrayList<>());
            }
            messageEntity.getChildren().add(findChild(entity, allList));
        }
    }
    return messageEntity;
}

tree 加层级Depth

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/**
   *  tree 加层级Depth
   * @param messageList
   * @param level
   * @return
   */
  private List<MyCloudDiskTypeCustom> treeSetDepth(List<MyCloudDiskTypeCustom> messageList ,Integer level) {
      // 子节点

      List<MyCloudDiskTypeCustom> childList = new ArrayList<>();
      for (MyCloudDiskTypeCustom entity : messageList) {
          entity.setDepth(level);
          if (entity.getChildren()!=null)
          {
              childList.add(entity);
          }

      }
      for (MyCloudDiskTypeCustom bean : childList) {
          if (bean.getChildren()!=null)
          {
            this.treeSetDepth(bean.getChildren(),level+1);
          }
      }

      return childList;
  }