我有一个extjs表单，我试图从中使用ext.ajax.request将参数发布到servlet。调用正在工作，正在调用servlet，但由于某些原因，未发送参数的值。我会发布我的代码，有人能告诉我我做错了什么吗。提前谢谢。
这是来自extjs表单的调用：

buttons: [{

        text: 'Search',
        handler: function(){

                          var fName = Ext.getCmp("fName").getValue();

                          Ext.Ajax.request({

                               url : 'LookUPCustomer',

                               method: 'POST',
                               headers: { 'Content-Type': 'application/json'},                    
                               params : fName, // this value isn't being passed to servlet

                               success: function ( result, request ) {
                                    var resultData1 = JSON.parse(result.responseText);
                               },

                               failure: function ( result, request ) {
                                 resultData = JSON.parse(xmlhttp.responseText);
                               }        

                          });

               }];

下面是servlet代码：

protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {

         PrintWriter out = response.getWriter();

         // value of fName is null, not being passed from the form
         String fName = request.getParameter("fName");

         // does some processing....

    // print back to the form
         response.setContentType("application/json");

     out.println(jsArray);      
   }