仿9GAG制作过程(五)

有话要说:

在做完了数据展示功能之后,就想着完善整个APP。发现现在后台非常的混乱,有好多点都不具备,比方说:图片应该有略缩图和原图,段子、评论、点赞应该联动起来,段子应该有创建时间等。

于是就重新设计了数据库,重新爬取了数据,重新设计了后台接口。

这次主要讲这次重构的主要内容。

数据库设计:

图片描述

一共设计了六张表,分别为

  • 段子表,主要存放每一个段子的图片等信息
  • 评论表,主要存放评论信息,评论可以上传图片
  • 用户表
  • 标签表,每条段子发表之前会自定义标签,该表存放的就是这些标签
  • 点赞记录表,因为用户点赞与段子之间是多对多的关系,因此要加一张表用来存放点赞记录
  • 段子标签关联表,因为段子和标签是多对多的,因此需要多一张表存放关联关系

接口设计:

图片描述

橙色的为表,咖啡色为接口。

目前设计了十四个接口,上图写明了各接口和相关的表之间的关系。

后台结构:

图片描述

bean包下为基本实体类;

implement包下为消息实体类的子类;

dao包为涉及到数据库的具体实现类;

servlet为接口类;

util为过程中用到的工具类。

具体例子:

下面以查询段子接口为例,介绍具体的结构。

bean类:

消息实体类:

 public class MessageEntity {
 
     // 返回信息描述
     private String reason;
     // 返回码
     private int errorCode;
 
     public String getReason() {
         return reason;
     }
 
     public void setReason(String reason) {
         this.reason = reason;
     }
 
     public int getErrorCode() {
         return errorCode;
     }
 
     public void setErrorCode(int errorCode) {
         this.errorCode = errorCode;
     }
 
 }

段子消息实体类:

 public class TopicMessageEntity extends MessageEntity {
 
     // 获取段子的结果
     private List<TopicEntity> result;
 
     public List<TopicEntity> getResult() {
         return result;
     }
 
     public void setResult(List<TopicEntity> result) {
         this.result = result;
     }
 
 }

段子实体类:

 public class TopicEntity {
 
     // 段子标识
     private int id;
     // 段子作者
     private String author = "";
     // 段子标题
     private String title = "";
     // 段子点赞数
     private int upvote;
     // 段子评论数
     private int commentCount;
     // 段子略缩图地址
     private String thumbNail = "";
     // 段子原图地址
     private String orgPicture = "";
     // 段子发表时间
     private String postTime = "";
     
     // 点的是赞还是踩,0代表没点,1代表赞,-1代表踩
     private int like = 0;
 
     public int getId() {
         return id;
     }
 
     public void setId(int id) {
         this.id = id;
     }
 
     public String getAuthor() {
         return author;
     }
 
     public void setAuthor(String author) {
         this.author = author;
     }
 
     public String getTitle() {
         return title;
     }
 
     public void setTitle(String title) {
         this.title = title;
     }
 
     public int getUpvote() {
         return upvote;
     }
 
     public void setUpvote(int upvote) {
         this.upvote = upvote;
     }
 
     public int getCommentCount() {
         return commentCount;
     }
 
     public void setCommentCount(int commentCount) {
         this.commentCount = commentCount;
     }
 
     public String getThumbNail() {
         return thumbNail;
     }
 
     public void setThumbNail(String thumbNail) {
         this.thumbNail = thumbNail;
     }
 
     public String getOrgPicture() {
         return orgPicture;
     }
 
     public void setOrgPicture(String orgPicture) {
         this.orgPicture = orgPicture;
     }
 
     public String getPostTime() {
         return postTime;
     }
 
     public void setPostTime(String postTime) {
         this.postTime = postTime;
     }
 
     public int getLike() {
         return like;
     }
 
     public void setLike(int like) {
         this.like = like;
     }
 
 }

这里和数据库表略有不同,主要是like字段。

like字段代表的是当前获取数据的人对该段子是否点了赞。

dao层:

查询段子方法:

 public List<TopicEntity> query(int topicId, int count, boolean after) {
         List<TopicEntity> topicList = new ArrayList<TopicEntity>();
 
         if (topicId <= 0) {
             topicId = 0;
         }
 
         if (count <= 0) {
             count = 10;
         }
 
         if (after) {
             queryAfter(topicId, count, topicList);
         } else {
             queryBefore(topicId, count, topicList);
         }
 
         return topicList;
     }
 private void queryAfter(int topicId, int count, List<TopicEntity> topicList) {
         String queryAfter = "SELECT * FROM 9gag_topics WHERE id > ? LIMIT ?";
 
         Connection conn = DatabaseUtil.getConnection();
         PreparedStatement pstmt = null;
         ResultSet rs = null;
 
         try {
             pstmt = conn.prepareStatement(queryAfter);
             pstmt.setInt(1, topicId);
             pstmt.setInt(2, count);
             rs = pstmt.executeQuery();
 
             while (rs.next()) {
                 TopicEntity topicEntity = new TopicEntity();
                 topicEntity.setId(rs.getInt("id"));
                 topicEntity.setAuthor(rs.getString("author"));
                 topicEntity.setTitle(rs.getString("title"));
                 topicEntity.setUpvote(rs.getInt("upvote"));
                 topicEntity.setCommentCount(rs.getInt("commentcount"));
                 topicEntity.setThumbNail(rs.getString("thumbnail"));
                 topicEntity.setOrgPicture(rs.getString("orgpicture"));
                 topicEntity.setPostTime(rs.getString("posttime"));
                 topicList.add(topicEntity);
             }
         } catch (SQLException e) {
             e.printStackTrace();
         } finally {
             DatabaseUtil.close(conn, pstmt, rs);
         }
     }
 private void queryBefore(int topicId, int count, List<TopicEntity> topicList) {
         String queryBefore = "SELECT * FROM 9gag_topics WHERE id < ? ORDER BY id DESC LIMIT ?";
 
         Connection conn = DatabaseUtil.getConnection();
         PreparedStatement pstmt = null;
         ResultSet rs = null;
 
         try {
             pstmt = conn.prepareStatement(queryBefore);
             pstmt.setInt(1, topicId);
             pstmt.setInt(2, count);
             rs = pstmt.executeQuery();
 
             while (rs.next()) {
                 TopicEntity topicEntity = new TopicEntity();
                 topicEntity.setId(rs.getInt("id"));
                 topicEntity.setAuthor(rs.getString("author"));
                 topicEntity.setTitle(rs.getString("title"));
                 topicEntity.setUpvote(rs.getInt("upvote"));
                 topicEntity.setCommentCount(rs.getInt("commentcount"));
                 topicEntity.setThumbNail(rs.getString("thumbnail"));
                 topicEntity.setOrgPicture(rs.getString("orgpicture"));
                 topicEntity.setPostTime(rs.getString("posttime"));
                 topicList.add(topicEntity);
             }
         } catch (SQLException e) {
             e.printStackTrace();
         } finally {
             DatabaseUtil.close(conn, pstmt, rs);
         }
 
         // 获取完数据之后逆序,因为查找的时候是逆序
         Collections.reverse(topicList);
     }

这三个方法实现了查询指定段子前(或者后)count条记录。

servlet层:

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         response.setContentType("text/json; charset=utf-8");
         PrintWriter out = response.getWriter();
 
         TopicMessageEntity message = new TopicMessageEntity();
         TopicDAO topicDao = new TopicDAO();
         UpvoteDAO upvoteDao = new UpvoteDAO();
         Gson gson = GsonUtil.getGson();
 
         request.setCharacterEncoding("utf-8");
         response.setCharacterEncoding("utf-8");
 
         int topicId = Integer.parseInt(request.getParameter("topicId"));
         int count = Integer.parseInt(request.getParameter("count"));
         boolean after = Boolean.parseBoolean(request.getParameter("after"));
         String author = request.getParameter("author");
 
         if (count <= 0) {
             message.setErrorCode(-1);
             message.setReason("count值不能为负数!");
             out.print(gson.toJson(message));
             return;
         }
 
         try {
             List<TopicEntity> topics = topicDao.query(topicId, count, after);
             
             // 判断作者是否点过赞
             if (author != null) {
                 List<UpvoteEntity> upvoteList = upvoteDao.findUpvoteByAuthor(author, true);
                 if (upvoteList != null) {
                     for (TopicEntity topic : topics) {
                         for (UpvoteEntity upvote : upvoteList) {
                             if (upvote.getLikedId() == topic.getId()) {
                                 int like = upvote.isLiked() ? 1 : -1;
                                 topic.setLike(like);
                             }
                         }
                     }                    
                 }
             }
             
             Collections.reverse(topics);
             message.setErrorCode(0);
             message.setReason("success");
             message.setResult(topics);
         } catch (Exception e) {
             message.setErrorCode(-1);
             message.setReason(e.getMessage());
         } finally {
             out.print(gson.toJson(message));
         }
 
     }

主要逻辑:查找到需要的段子→遍历段子→如果段子被点过赞或者踩,就把段子相应字段更改为赞或者踩→由于查出来的数据时顺序的,要改为逆序展示。

反思:

这次主要重构了后台的设计逻辑,其实还有好多不完备的地方。

通过这次重构,明白了一个要点。要做一件事情首先要规划好,首先是设计,把一切的流程,框架设计好之后按部就班的做。这样做出来的东西才会比较好。

否则在过程中会很混乱,严重影响效率。

预告:

下一章准备讲述点赞的逻辑,因为点赞的逻辑比较复杂。

大家如果有什么疑问或者建议可以通过评论或者邮件的方式联系我,欢迎大家的评论~