Ajax無法正常工作？

Question

這裏是我的Ajax代碼

$('.AllTaskDownloadButton').live('click', '.CheckBoxesForDownload', function(){ 

    var n = $("input:checked.CheckBoxesForDownload").length; 
    var arr=[] 
    for(i=0;i<n;++i){ 
     arr.push($($("input:checked.CheckBoxesForDownload")[i]).val()) 
    } 
    alert(arr) 
    //passing requestId to servlet 
    $.ajax({ 
     url:"/test/DownloadDeleteTask", 
     type:"POST", 
     dataType:'json', 
     data: {requestIds:arr, 
       operationType:'download' }, 
     success:function(result){ 
      alert(result); 
      dowloadTasks(); 
     } 
    });//ajax 

    }); 

，這裏是我的servlet代碼：

PrintWriter out = response.getWriter(); 

String operationType = request.getParameter("operationType"); 

if (operationType.equalsIgnoreCase("download")) { 

     out.print("download"); 

    }// if 

但我downloadTasks()是沒有得到調用。

請幫忙解決這個問題？

Answer 1

字符串化的Ajax調用的數據部分的JSON和添加的contentType：

$.ajax({ 
    url: "/test/DownloadDeleteTask", 
    type: "POST", 
    dataType: "json", 
    contentType: "application/json; charset=utf-8", 
    data: JSON.stringify({requestIds:arr, 
     operationType:"download" 
    }), 
    success:function(result){ 
     alert(result); 
     dowloadTasks(); 
    } 
});