Question

我正在阅读一本书来学习ajax，因为我的Servlet响应（只是文本）没有出现在我的JavaScript警报中，所以我陷入困境。单击该按钮时，它会调用JavaScript函数，然后异步发送http请求。

我不明白为什么String没有显示在响应中。感谢任何人都可以解决这个问题。

编辑：此外，在发送＆＃34; get＆＃34;之后，我得到状态代码200请求。当我在控制台下查看firebug时，我看到带有200状态代码的Get请求。有3个选项卡 - Params，Headers和XML。在Params下我看到我在请求中发送的虚拟参数。在标题下有2个节点 - 响应标头和请求标头。当我展开Response Header节点时，我看到一个名为content-length的东西，后面有一个0。这是否意味着我的回答中没有任何内容？

这是我的HTML

<html>
 <head>
  <title>Boards 'R' Us</title>
  <link rel="stylesheet" type="text/css" href="boards.css" media="screen" />
  <script type="text/javascript" src="ajax.js"> </script>
  <script type="text/javascript" src="text-utils.js"> </script>
  <script type="text/javascript" src="boards.js"> </script>
 </head>

 <body>
  <h1>Boards 'R' Us :: How Much Butt We're Kicking</h1>
  <div id="boards">
   <table>
    <tr><th>Snowboards Sold</th>
     <td><span id="boards-sold">1672</span></td></tr>
    <tr><th>What I Sell 'em For</th>
     <td>$<span id="boards-price">249.95</span></td></tr>
    <tr><th>What it Costs Me</th>
     <td>$<span id="boards-cost">84.22</span></td></tr>
   </table>
   <table>
    <tr><th>Boots Sold</th>
     <td><span id="boots-sold">312</span></td></tr>
    <tr><th>What I Sell 'em For</th>
     <td>$<span id="boots-price">175.47</span></td></tr>
    <tr><th>What it Costs Me</th>
     <td>$<span id="boots-cost">54.23</span></td></tr>
   </table>
   <table>
    <tr><th>Bindings Sold</th>
     <td><span id="bindings-sold">82</span></td></tr>
    <tr><th>What I Sell 'em For</th>
     <td>$<span id="bindings-price">146.92</span></td></tr>
    <tr><th>What it Costs Me</th>
     <td>$<span id="bindings-cost">98.03</span></td></tr>
   </table>
   <h2>Cash for the Slopes: 
    $<span id="cash">318936.42</span></h2>
   <form>
    <input value="Show Me the Money" type="button" 
           onClick="getNewTotals();" /> 
   </form>
  </div>
 </body>
</html>

和我的JavaScript

function getNewTotals() {
    console.log("Getting new totals");
    var url = "boards.do";
    url = url + "?dummy=" + new Date().getTime();
    request.open("GET", url, true);
    request.onreadystatechange = updatePage;
    request.send(null);
}

function updatePage() {
    if (request.readyState == 4) {
        if (request.status == 200) {
            var reply = request.responseText;
            alert("returned: " + reply);
        } else {
            alert("Error! Request status = " + request.status);
        }
    }
}

和我的Servlet

import java.io.IOException;
import java.io.PrintWriter;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.gmail.gmjord.controller.BoardSalesController;

/**
 * Servlet implementation class BoardSalesController
 */
//@WebServlet("/BoardSalesController")
public class BoardSalesController extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final Logger LOGGER = Logger.getLogger(BoardSalesController.class.getClass().getName());
    private static final Level INFO = Level.INFO;
    private static final Level[] LEVELS = {Level.SEVERE, Level.WARNING, Level.INFO, Level.CONFIG,
        Level.FINE, Level.FINER, Level.FINEST};

    /**
     * @see HttpServlet#HttpServlet()
     */
    public BoardSalesController() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        LOGGER.log(INFO, "in doGet()");
        String info = request.getParameter("dummy");
        LOGGER.log(INFO, "Request info: " + info);
        response.setContentType("text/plain");
        response.setCharacterEncoding("UTF-8");
        String reply = "Do you see this?";
        response.getWriter().write(reply);


    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

Answer 1

我了解到您正在正确调用servlet并获得http-header状态= 200的响应，但是您没有收到字符串内容，不是吗？

然后我认为你必须在编写器上调用flush()来提交响应。如果您查看getWriter()中javax.servlet.ServletResponse javax.servlet.http.HttpServletResponse servlet container的界面，您可以看到：

在PrintWriter上调用flush（）会提交响应。

然而，这通常不是必需的，因为doGet为您做了这些，但是在您的情况下似乎不是这样尝试在您的servlet上的String reply = "Do you see this?"; PrintWriter writer = response.getWriter(); writer.write(reply); writer.flush();方法中使用此代码：

{{1}}

希望这有帮助，

为什么servlet响应没有显示在我的JavaScript中

1 个答案: