将会话值附加到 Java 中的数组

Question

我正在尝试处理 Java 中的会话。每次有人进入新页面时，我都需要增加视图值，但每个用户每次会话只增加一次。目前下面的代码并没有这样做，它一直在增加它。我认为问题可能是每次加载页面时，arraylist 都会再次新建？我不确定如何处理这个问题。因为刷新后对象不会留在数组中。

处理会话并尝试增加计数的代码 // 获取图片的名字 session.setAttribute("pictureName", pictureName);

    // create a list of objects that will store all the pages a user visits
    ArrayList<String> listOfObjects = new ArrayList<String>();

    // make a image_id variable but assign it the value of the page name
    String image_id = (String) session.getAttribute("pictureName");

    // go and compare each element in the list, to the id.
    // This should NOT match on the first viewing since it's the first time the user
    // visits the page
    // this should then increment the view count
    if (Utilities.isFirstVisit(listOfObjects, image_id) == true) {
        Utilities.IncreaseCount(out, pictureName);
        out.println("its worked");

    } else {
        // if a match is found then the user has already visited this page
        // therefore don't increment the view count for the love of christ
        out.println("A match was found");

    }

调用的方法将对象添加或不添加到数组列表中

public static boolean isFirstVisit(ArrayList <String> listOfObjects,
            String image_id) {
        System.out.println(listOfObjects);
        System.out.println(image_id);

    if(listOfObjects.contains(image_id)) {
        System.out.println("It does contain");
        System.out.println(image_id);
        return false;
    }

    else { 
        listOfObjects.add(image_id);
        System.out.println("It does not contain");
        System.out.println(image_id);
        return true;
        }
    }

增加浏览量的方法

//Increase the access count on the picture
    public static void IncreaseCount(PrintWriter out, String pictureName) {

        Connection con = null;
        try { // Connect to the database
            con = openConnection(out);
        } catch (Exception e) { // Failed to open the connection
            out.println("<P>" + e.getMessage());
            return;
        }

        try {

            Statement stmt = con.createStatement();
            String query;
            ResultSet rs1;

            query = "UPDATE Statistics SET AccessCount = AccessCount + 1 WHERE PictureNo = (SELECT PictureNo FROM Pictures WHERE FileName = '"
                    + pictureName + "')";

            stmt.executeUpdate(query);

            stmt.close();

        } catch (SQLException ex) {
            out.println("<P>SQLException: " + ex.getMessage());
        }

    }

#

更新只是在每个会话中更新一张图片，而不是在每个会话中更新所有访问过的图片

   if(session.getAttribute("myVisitedPages") == null) {
           ArrayList<String> listOfPages = new ArrayList<String>();

           session.setAttribute("myVisitedPages", listOfPages);

            if (Utilities.isFirstVisit(listOfPages, pictureName) == true) {
                Utilities.IncreaseCount(out, pictureName);
                out.println("its worked");

            } 
       }

Answer 1

您必须在会话中存储访问过的页面列表。

流程如下：

1. 尝试从“myVisitedPages”会话中获取属性
2. 第一次是null。创建一个new ArrayList()，使用setAttribute 将其附加到会话中，并为其添加第一个页面ID。
3. 第二次以后，该列表将作为会话属性提供，您可以获取该列表并查看该列表。

（顺便说一句，我不确定为什么您当前访问的页面 ID 需要出现在会话中。）

更新后。 If 不应该嵌套：

  ArrayList<String> listOfPages = session.getAttribute("myVisitedPages");
  if(listOfPages == null) {
       listOfPages = new ArrayList<String>();

       session.setAttribute("myVisitedPages", listOfPages);
   }

   if (Utilities.isFirstVisit(listOfPages, pictureName) == true) {
       Utilities.IncreaseCount(out, pictureName);
       out.println("its worked");
   } 

Answer 2

好吧，据我了解，你也想增加 每次有新访问时的计数器也是网络 看法 如果是这样。 声明一个

HttpSession obj = request.getSession();
obj.setSessionAttribute("image_id", null);
  
  If (obj.getAttribute("image_id") == null){
     Write_to_db();
     string value="user counted";
     obj.setSessionAttribute("image_id", value); 
     }