javascript - 如何使用 Javascript/AJAX 和 Java Servlet 逐步设置 HTML 表？

Question

大家好!我在开发一个小网络应用程序时遇到问题。目标是从服务器上的指定文件夹中的文件中搜索特定单词。

为此，我使用 java.io.File 和 BufferReader 实现了递归算法。当我得到结果时，我使用 jsp 文件中的脚本将它们放在一个表中:

// Posting founded files in a table.
var files = response.getElementsByTagName("file");
// -> Creating the results table.
var table = "<table width=\"100%\">\n";

for (var i = 0, c = files.length; i < c; i++) {
// -> Building the number of apparence in each file.
var nb = files[i].getAttribute("nb");
var nbSentence = "";
if (nb == 1) { nbSentence = nb + " time in this file."; }
else { nbSentence = nb + " times in this file."; }

// Building and filling the table. 
if (i % 2 == 0) { table += "<tr class=\"pair\"><td><a href=" + files[i].firstChild.nodeValue + " target=\"_blank\" >"
                + files[i].getAttribute("name") + "</a></td><td>" + nbSentence + "</td></tr>\n"; }
else { table += "<tr class=\"impair\"><td><a href=" + files[i].firstChild.nodeValue + " target=\"_blank\" >"
                + files[i].getAttribute("name") + "</a></td><td>" + nbSentence + "</td></tr>\n"; }
}
table += "</table>\n";
// -> To end the procedure, we had the table to the right div.
document.getElementById("files").innerHTML = table;

我的问题是，使用这段代码，所有结果都会一次性打印在目标表中。每次在算法中找到文件时，我希望看到结果一一出现。

我尝试在 onreadystatestage 函数中将就绪状态更改为“3”:

xhr.onreadystatechange = function() {
if (xhr.readyState >= 3 && (xhr.status == 200 || xhr.status == 0)) {
    callback(xhr.responseXML);
    document.getElementById("loader").style.display = "none";
    document.getElementById("btn").value = "Search";
} else if (xhr.readyState < 3) {
    document.getElementById("loader").style.display = "inline";
    document.getElementById("btn").value = "Cancel";
}
};

但这并没有改变任何事情。有人有想法吗？如何将创建的每个文件一一发送？我不必在 servlet 类中执行此操作吗？

servlet 类中的 for 指令:

// If the input word name isn't empty, the algorithm is launched.
if (null != wordToSearch && !"".equals(wordToSearch))
{
lstFiles.clear();
searching(new File(contextPath), wordToSearch);

int n = lstFiles.size();
// Priting a message that indicate how many files have been found with the word to search.
emptyFieldMessage = n + " files has been found containing the word '" + wordToSearch + "'!";
output.append("<message>").append(emptyFieldMessage).append("</message>\n");
output.append("<lstFiles>\n");
// Then, files list with :
// - File path in "name" parameter,
// - Number of apparence of the word in "nb" parameter,
// - Formatted path as the value.
for(int i = 0; i < n; i++)
{
    output.append("<file name=\"" + lstFiles.get(i) + "\" nb=\"" + lstNbApparence.get(i) + "\" >").append(lstFilesPath.get(i)).append("</file>\n");
}
output.append("</lstFiles>\n");
}

为了更完整，整个脚本代码:

<script>
// Creating xhr variable.
var xhr = null;

// Creating the "Search" button function.
function request(callback) {

   // "Cancel" button case.
   if (xhr && xhr.readyState != 0)
   {
       xhr.abort();
   }
   // "Search" button case.
   else
   {
       // Calling the good function from external file.
       xhr = getXMLHttpRequest();

       // Callback and loading icon management.
       xhr.onreadystatechange = function() {
        if (xhr.readyState >= 3 && (xhr.status == 200 || xhr.status == 0)) {
            callback(xhr.responseXML);
            document.getElementById("loader").style.display = "none";
            document.getElementById("btn").value = "Search";
        } else if (xhr.readyState < 3) {
            document.getElementById("loader").style.display = "inline";
            document.getElementById("btn").value = "Cancel";
        }
      };

      // Calling the Servlet in charge of the recursion algorithm.
      var input = encodeURIComponent(document.getElementById("wordName").value);
      xhr.open("GET", "/webApp_Search_Merge/ActionServlet?wordName=" + input, true);
      xhr.send(null);
      }
}

// Creating the reponse function.
function readData(response) {

if (null != response)
{
    // Posting the message include in the XML file sending back by the Servlet.
    var message = response.getElementsByTagName("message");
    document.getElementById("message").innerHTML = message[0].firstChild.nodeValue;

    // Posting founded files in a table.
    var files = response.getElementsByTagName("file");
    // -> Creating the results table.
    var table = "<table width=\"100%\">\n";

    for (var i = 0, c = files.length; i < c; i++) {
        // -> Building the number of apparence in each file.
        var nb = files[i].getAttribute("nb");
        var nbSentence = "";
        if (nb == 1) { nbSentence = nb + " time in this file."; }
        else { nbSentence = nb + " times in this file."; }

        // Building and filling the table. 
        if (i % 2 == 0) { table += "<tr class=\"pair\"><td><a href=" + files[i].firstChild.nodeValue + " target=\"_blank\" >"
            + files[i].getAttribute("name") + "</a></td><td>" + nbSentence + "</td></tr>\n"; }
        else { table += "<tr class=\"impair\"><td><a href=" + files[i].firstChild.nodeValue + " target=\"_blank\" >"
            + files[i].getAttribute("name") + "</a></td><td>" + nbSentence + "</td></tr>\n"; }
    }
    table += "</table>\n";
    // -> To end the procedure, we had the table to the right div.
    document.getElementById("files").innerHTML = table;
}

}

提前感谢您的帮助，托马斯。

Answer 1

我尝试设置一个工作演示，但没有结果。我也在寻找为什么我找不到“ sleep ”函数并在 1000 毫秒后重新执行或任何你想要的方法。已经找到了答案，但我认为这并不是您所期望的:

A sleep function will kill the browser and possibly the machine. Javascript is single threaded, so the browser will block while this executes, and the loop itself will just take up a lot of CPU. I’ve heard of some libraries that actually do sleep correctly in an asynchronous manner, but I can’t remember the name right now.

---

This is a very bad idea. JavaScript is single threaded so while that for loop is running nothing else can execute (js timers, browser events, even the UI in most browsers). Try to sleep for 5 or more seconds and the browser will even warn the user that a script is running slowly.

Just use setTimeout.

还谈到了 sleep 功能Native Javascript 。看起来就像是一个框架之类的东西。您可以下载并自行尝试。我对此不能说什么，因为我从未测试过，这只是我在互联网上发现的。

很抱歉给您带来坏消息。