Java递归获取评论列表

「爱情、让人受尽委屈。」 2022-07-12 10:43 172阅读 0赞

递归算法是一种直接或间接地调用自身的算法。在计算机编写程序中，递归算法往往使算法的描述简洁而且易于理解，譬如获取具有明显父子级结构的数据时（部门树、评论列表等等）。

Service层关键代码

public List<CommentTreeVo> getCommentTree(String topicId,String type) {
    		List<CommentTreeVo> list=null;
    		try {
    			list=getTree(topicId,type);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		
    		return  list;
    	}
    	public List<CommentTreeVo> getTree(String topicId,String type)  throws Exception{
    		CommentTreeVo root = new CommentTreeVo(0, "root");
    		addTree(root,topicId,type);
    		List<CommentTreeVo> treeList=new ArrayList<CommentTreeVo>();
    		treeList.add(root);
    		return treeList;
    	}
    
    	private void addTree(CommentTreeVo parent,String topicId,String type) {
    		List<CommentHistory> historyList = commentHistoryDao.findCommentByParentId(parent.getId(),topicId,type);
    		if (historyList != null && historyList.size() > 0) {
    			if (parent.getChildren() == null) {
    				parent.setChildren(new ArrayList<CommentTreeVo>());
    			}
    			for (CommentHistory temp : historyList) {
    				CommentTreeVo vo = new CommentTreeVo();
    				vo.setId(temp.getId());
    				vo.setText(temp.getWords());
    				vo.setCreateTime(temp.getCreateTime());
    				SimpleUser fromUser = temp.getFromUser();
    				if (fromUser != null) {
    					vo.setUserId(fromUser.getId());
    					vo.setFromUserName(fromUser.getUsername());
    					vo.setFromUserAvatarUrl(fromUser.getHeadImage().getUrl());
    				}
    				SimpleUser toUser = temp.getToUser();
    				if (toUser != null) {
    					vo.setToUserId(toUser.getId());
    					vo.setToUserName(toUser.getUsername());
    					vo.setToUserAvatarUrl(toUser.getHeadImage().getUrl());
    				}
    				parent.getChildren().add(vo);
    				addTree(vo,topicId,type);
    			}
    			
    		}
    	}

CommentHistory实体

@Entity
    @Table(name = "comment_history")
    public class CommentHistory implements Serializable{
    
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    	@Id
    	@GeneratedValue(strategy = GenerationType.IDENTITY)
    	private long id;	
    	@OneToOne(cascade =  {CascadeType.REFRESH},optional = false)  
    	@JoinColumn(name = "userId")  
    	private SimpleUser fromUser;
    	private String topicId;
    	private long createTime;
    	private String type;  // 1视频 2 咨询 3电音节
    	private long pid;
    	@OneToOne(cascade =  {CascadeType.REFRESH},optional = false)  
    	@JoinColumn(name = "toUserId")  
    	private SimpleUser toUser;
    	private String words;
    	
    	public CommentHistory(){
    		this.createTime=System.currentTimeMillis();
    	}
    	public long getId() {
    		return id;
    	}
    	public void setId(long id) {
    		this.id = id;
    	}
    	
    	public String getTopicId() {
    		return topicId;
    	}
    	public void setTopicId(String topicId) {
    		this.topicId = topicId;
    	}
    	public String getType() {
    		return type;
    	}
    	public void setType(String type) {
    		this.type = type;
    	}
    	public long getCreateTime() {
    		return createTime;
    	}
    	public void setCreateTime(long createTime) {
    		this.createTime = createTime;
    	}
    	public long getPid() {
    		return pid;
    	}
    	public void setPid(long pid) {
    		this.pid = pid;
    	}
    	public String getWords() {
    		return words;
    	}
    	public void setWords(String words) {
    		this.words = words;
    	}
    	public SimpleUser getFromUser() {
    		return fromUser;
    	}
    	public void setFromUser(SimpleUser fromUser) {
    		this.fromUser = fromUser;
    	}
    	public SimpleUser getToUser() {
    		return toUser;
    	}
    	public void setToUser(SimpleUser toUser) {
    		this.toUser = toUser;
    	}
    	
    }

CommentTreeVo

public class CommentTreeVo  {
    	private long id;
    	private int userId;
    	private String fromUserAvatarUrl;
    	private String fromUserName;
    	private int toUserId;
    	private String toUserAvatarUrl;
    	private String toUserName;
    	private long createTime;
    	private String text;
    	private List<CommentTreeVo> children;
    	private String topicId;
    	private String type;
        public CommentTreeVo(){
    		
    	}
    	public CommentTreeVo(int id, String text) {
    		this.id = id;
    		this.text = text;
    	}
    	public long getId() {
    		return id;
    	}
    	public void setId(long id) {
    		this.id = id;
    	}
    	public String getText() {
    		return text;
    	}
    	public void setText(String text) {
    		this.text = text;
    	}
    	public List<CommentTreeVo> getChildren() {
    		return children;
    	}
    	public void setChildren(List<CommentTreeVo> children) {
    		this.children = children;
    	}
    	public int getUserId() {
    		return userId;
    	}
    	public void setUserId(int userId) {
    		this.userId = userId;
    	}
    	public int getToUserId() {
    		return toUserId;
    	}
    	public void setToUserId(int toUserId) {
    		this.toUserId = toUserId;
    	}
    	public long getCreateTime() {
    		return createTime;
    	}
    	public void setCreateTime(long createTime) {
    		this.createTime = createTime;
    	}
    	public String getFromUserAvatarUrl() {
    		return fromUserAvatarUrl;
    	}
    	public void setFromUserAvatarUrl(String fromUserAvatarUrl) {
    		this.fromUserAvatarUrl = fromUserAvatarUrl;
    	}
    	public String getFromUserName() {
    		return fromUserName;
    	}
    	public void setFromUserName(String fromUserName) {
    		this.fromUserName = fromUserName;
    	}
    	public String getToUserAvatarUrl() {
    		return toUserAvatarUrl;
    	}
    	public void setToUserAvatarUrl(String toUserAvatarUrl) {
    		this.toUserAvatarUrl = toUserAvatarUrl;
    	}
    	public String getToUserName() {
    		return toUserName;
    	}
    	public void setToUserName(String toUserName) {
    		this.toUserName = toUserName;
    	}
    	public String getTopicId() {
    		return topicId;
    	}
    	public void setTopicId(String topicId) {
    		this.topicId = topicId;
    	}
    	public String getType() {
    		return type;
    	}
    	public void setType(String type) {
    		this.type = type;
    	}
    	
    
    }

controller和dao层代码略

comment\_history表的结构及数据：

![Center][]

得到的json数据如下：

{
      "code": "200",
      "msg": "调用成功",
      "stat": "ok",
      "dataList": [
        [
          {
            "id": 0,
            "userId": 0,
            "fromUserAvatarUrl": null,
            "fromUserName": null,
            "toUserId": 0,
            "toUserAvatarUrl": null,
            "toUserName": null,
            "createTime": 0,
            "text": "root",
            "children": [
              {
                "id": 1,
                "userId": 5,
                "fromUserAvatarUrl": "/uploadFile/person/cropperImage/c8d23098-c4dd-4978-a6f2-1584285306f7.thumb.224_0.jpeg",
                "fromUserName": "李秀才",
                "toUserId": 0,
                "toUserAvatarUrl": null,
                "toUserName": null,
                "createTime": 1487583133008,
                "text": "我是一楼。",
                "children": [
                  {
                    "id": 2,
                    "userId": 5,
                    "fromUserAvatarUrl": "/uploadFile/person/cropperImage/c8d23098-c4dd-4978-a6f2-1584285306f7.thumb.224_0.jpeg",
                    "fromUserName": "李秀才",
                    "toUserId": 0,
                    "toUserAvatarUrl": null,
                    "toUserName": null,
                    "createTime": 1487583178371,
                    "text": "我是二楼。",
                    "children": null,
                    "topicId": null,
                    "type": null
                  },
                  {
                    "id": 3,
                    "userId": 5,
                    "fromUserAvatarUrl": "/uploadFile/person/cropperImage/c8d23098-c4dd-4978-a6f2-1584285306f7.thumb.224_0.jpeg",
                    "fromUserName": "李秀才",
                    "toUserId": 0,
                    "toUserAvatarUrl": null,
                    "toUserName": null,
                    "createTime": 1487583178371,
                    "text": "我是三楼。",
                    "children": null,
                    "topicId": null,
                    "type": null
                  }
                ],
                "topicId": null,
                "type": null
              },
              {
                "id": 4,
                "userId": 6,
                "fromUserAvatarUrl": "/uploadFile/person/cropperImage/2a4e72ee-1701-4380-a43e-3cb88c72f586.jpg",
                "fromUserName": "呵呵",
                "toUserId": 0,
                "toUserAvatarUrl": null,
                "toUserName": null,
                "createTime": 1487583178371,
                "text": "一出手就是十个字。",
                "children": null,
                "topicId": null,
                "type": null
              }
            ],
            "topicId": null,
            "type": null
          }
        ]
      ]
    }

[Center]: /images/20220710/29313260df37451f9f352c2d311cc4ed.png