easyUI-form表单提交，正确返回但是不执行success

form表单

        submit0 :function(){
                  $("#flowSubmmit").form('submit',{  
                        type : 'POST',  
                        dataType : "json", 
                        url : '/flow/submitTask.do',  
                        success : function(result) {
                            var s=result;
                            var result = eval('(' + result + ')');  
                            if (result.message==("ok")) {  
                                $.messager.alert('提示!', '成功','info',  
                                        function() {  
                                            $('#supplementaryBudget').dialog('close');  
                                        });  
                            } else {  
                                $.messager.confirm('提示',"失败!");  
                                $('#supplementaryBudget').dialog('close');  
                            }  
                        }  
                    });

            },

请求头

Host     localhost:8080
User-Agent   Mozilla/5.0 (Windows NT 6.1; W…) Gecko/20100101 Firefox/55.0
Accept   text/html,application/xhtml+xm…plication/xml;q=0.9,*/*;q=0.8
Accept-Language  zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding  gzip, deflate
Content-Type     application/x-www-form-urlencoded
Content-Length   275
Referer  http://localhost:8080/basic/toTaskManager.do
Cookie   JSESSIONID=BB393F5999EC3BF6A85CBE64B96264BB
Connection   keep-alive
Upgrade-Insecure-Requests    1

响应头

Server  Apache-Coyote/1.1
Content-Type    text/plain;charset=UTF-8
Content-Length  16
Date    Thu, 28 Sep 2017 08:49:47 GMT

问题：
form表单提交，响应类型text/plain，不走sucess，直接结束
但是页面显示内容如下

即使后面我返回text/html，json也没有用。