本文详细介绍Ajax基础教程（4）- 实现基本Ajax技术 4.5 显示进度条
这个例子的服务器代码“模拟”了一个长时间运行的事务（见代码清单4-10）。在真实环境中，这期间可能还要同时创建多个新实例并注册，之前还需要客户发出请求。为简单起见，我们忽略了这点，也没有编写线程代码。
代码清单4-10 ProgressBarServlet.java
package ajaxbook.chap4;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ProgressBarServlet extends HttpServlet {
private int counter = 1;
/** Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String task = request.getParameter("task");
String res = "";
if (task.equals("create")) {
res = "<key>1</key>";
counter = 1;
}
else {
String percent = "";
switch (counter) {
case 1: percent = "10"; break;
case 2: percent = "23"; break;
case 3: percent = "35"; break;
case 4: percent = "51"; break;
case 5: percent = "64"; break;
case 6: percent = "73"; break;
case 7: percent = "89"; break;
case 8: percent = "100"; break;
}
counter++;
res = "<percent>" + percent + "</percent>";
}
PrintWriter out = response.getWriter();
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
out.println("<response>");
out.println(res);
out.println("</response>");
out.close();
}
}图4-10显示了实际工作中的进度条，图4-11显示了完成时的情况。
图4-10 进度条示例
图4-11 进度条完成
来源：CSDN 责编：豆豆技术应用
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