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Trying to make an Ajax call to a web form method and getting an internal server error. I have tried almost all solutions to similar questions

The function getClientData() gets called from one of the anchor tags in a grid's column. The anchor tag has a couple of Data-Tags which are passed to the code behind method. I have to perform some DB operation through these parameters but before that I wanted to make sure if this prototype would work.
This is how the anchor tag looks:
Show
This is my Javascript method:
function getClientData() {
//var dataValue = { "keyData": this.event.target.getAttribute("data-kt"), "valueData": this.event.target.getAttribute("data-kv")};
$.ajax({
type: "GET",
url: "Clients.aspx/GetClientData",
contentType: 'application/json; charset=utf-8',
data: JSON.stringify({ keyData: this.event.target.getAttribute("data-kt"), valueData: this.event.target.getAttribute("data-kv")}),
dataType: 'json',
error: function (error) {
alert(error.statusText);
},
success: function (result) {
alert("Success: " + result );
}
});
}
I put a break point here and it never gets triggered. This is my web method in the code behind file:
[WebMethod]
[ScriptMethod(UseHttpGet = false)]
public string GetClientData(string keyData, string valueData)
{
string result = string.Empty;
if (!string.IsNullOrEmpty(keyData) && !string.IsNullOrEmpty(valueData))
{
result = "Decrypted String!";
}
return result;
}
This is the URL that gets created for the POST request "http://localhost:60825/Clients.aspx/GetClientData?{%22keyData%22:%22Cpuqsrtsotmfegrhsi-jikdbCvuwsxtcodmeelrmI-Dn-ovpcqSresctrfegthKiejy%22,%22valueData%22:%221p7q9%22}". Please let me know if I am doing something wrong.

I am not sure how you configured routing but based on your API method (code behind) your data should be formatted in following manner:
Method 1:
http://localhost:60825/Clients.aspx/GetClientData?keyData=Cpuqsrtsotmfegrhsi-jikdbCvuwsxtcodmeelrmI-Dn-ovpcqSresctrfegthKiejy&valueData=1p7q9
As you can see, instead passing stringified JSON object I am sending data in format of query string where keyData and valueData has corresponding values.
Method 2:
If you prefer to send stringified JSON you can modify your Payload in URL like this:
http://localhost:60825/Clients.aspx/GetClientData?data=%7BkeyData%22%3A%22Cpuqsrtsotmfegrhsi-jikdbCvuwsxtcodmeelrmI-Dn-ovpcqSresctrfegthKiejy%22%2C%22valueData%22%3A%221p7q9%22%7D
Here I am sending stringified JSON as data parameter in query string. For that purpose your code behing method needs to be like this:
[WebMethod]
[ScriptMethod(UseHttpGet = false)]
public string GetClientData(string data)
{
string result = string.Empty;
if (!string.IsNullOrEmpty(keyData) && !string.IsNullOrEmpty(valueData))
{
result = "Decrypted String!";
}
return result;
}

JQuery/AJAX call is not hitting Spring MVC controller

I am trying to verify username and other fields while creating a change password page.The problem is AJAX call in Jquery script is not hitting my controller.i tried giving hard coded path also in url field of the ajax request.
Below is my Script
this checkUname function is triggering on onblur event from one of the input field.
<script type="text/javascript">
function checkUname()
{
// get the form values
var uName = $('#username').val();
var secQues = $('#secQues').val();
var secAns = $('#secAns').val();
var dataObject = JSON.stringify({
'uName' : uName,
'secQues': secQues,
'secAns' : secAns
});
$.ajax({
url:"validateCredentials.do" ,
type: "POST" ,
data: dataObject ,
contentType: "application/json; charset=utf-8" ,
dataType : 'json' ,
success: function(response)
{
alert(response);
} ,
error: function()
{
alert('Error fetching record.... Sorry..');
}
});
}
</script>
This is my MVC controller
#Controller
public class ArsController
{
#RequestMapping(value="validateCredentials.do", method = RequestMethod.POST)
public String changePass(#RequestParam("uName") String uName ,#RequestParam("secQues")String secQues,
#RequestParam("secAns") String secAns)
{
System.out.println("AJAX request");
Users dummyUSer = null;
String msg = null;
try
{
dummyUSer = servObj.findUser(uName);
}
catch (ArsException e)
{
System.out.println("error occurred while validating user data during password change");
e.printStackTrace();
}
if(dummyUSer == null)
{
msg = "No user exists with this username";
}
else
{
if(!secQues.equals(dummyUSer.getSecQues()))
{
msg = "Security question is not correct";
}
else
{
if(!secAns.equals(dummyUSer.getSecAns()))
{
msg = "Security answer does not match";
}
}
}
return msg;
}

Instead of using RequestParam in controller, you should use String. Because when we are posting JSON data it will not come as individual parameters in Request, instead it will be received as String in your controller. Once you get the String convert it to JSON object and then get your values accordingly.

try remove content-type and data-type.
You are not sending a json that should be parsed in a object, you are sending controller's parameters.
The way to do that is using an object in the Ajax 's data (as you did) but without the content-type or data-type that saying "I'm sending one json parameter"

How I send the result of the AJAX back to the JSP?

I post some via AJAX in my servet from my jsp
$.ajax({
url: 'myServlet?action=FEP',
type: 'post',
data: {machine: i, name: txt}, // i, txt have some values.
success: function (data) {
alert('success');
}
});
and in my Serlvlet
String jspAction = request.getParameter("action");
//...
if(jspAction.equals("FEP")){
int idMachine = Integer.parseInt(request.getParameter("machine"));
String name = request.getParameter("name");
double value = actions.getValue(idMachine, name); //<-- this variable I want to send it back to the JSP.
}
The data are sent succesfully. However I haven't understand how I send back the vaule to the jsp..

returning a string would go as follows:
response.getWriter().write("a string");
return null;
If you want to return json, you can use many libraries like: http://www.json.org/
This would result in something like following code:
response.setContentType("application/json");
JSONObject jsonObject = new JSONObject();
double aDouble = 38d;
jsonObject.put("returnValue", aDouble);
response.getWriter().write(jsonObject.toString());
return null;

Use
response.getWriter().write(value);
return null;
And in your ajax success block access the value.
See the following link for more understanding http://www.javacodegeeks.com/2014/09/jquery-ajax-servlets-integration-building-a-complete-application.html

how can pass array to java servlet

On my jsp, this is my code :
$('.save').on("click",function(){
var array = $.map($('table tr'), function (val, i) {
var obj = {}, inputs = $(val).find('td input:not(:hidden)');
obj[inputs.filter(':first').val()] = $.map(inputs.not(':first'), function (val, i) {
return val.value;
});
return obj;
});
var data = JSON.stringify(array);
$.post("Controller.html", data, function(response) {
/// i dont know what to put here,so i think this where i get trouble with
});
});
but still data is null when i check on servlet.
this is my servlet :
protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String data=request.getParameter("data");
if (data== null) {
System.out.println("null");
}
RequestDispatcher view = request.getRequestDispatcher("/page.jsp");
view.forward(request, response);
}
fiddle here

First you need to send the data, you can use an ajax post method:
$.post("yourservlet", data=JSON.stringify(array), function(response) {
// handle response from your servlet.
alert(response)
});
In servlet, you retrieve the data with the command:
String data=request.getParameter("data");
Then you need to parse the json, you can use a library like JSON simple:
Object obj = JSONValue.parse(data);
JSONArray array = (JSONArray) obj;
Or you can manually parse it. Based on your code, your json string will look like this:
data = "[{'orange':['1.00','5']},{'apple':['2.00','5']}]";
You can use split() method or StringTokenizer to separate each object, but you should write your own parser method, for this you can find many tutorials on google.

Javascript is in client-side. And java servlet is for server-side.
You must use ajax to make a call from client-side to your servlet.

How to download file from System.Web.HttpContext.Current.Response.BinaryWrite(byteArray); from javascript instead of C#

I have a C# method that works if you call it from another C# method, but not from javascript. How do I make it work from my ajax call?
I need to get a file based on an ID that is passed in, so I have an ajax post with the statusID. That ID is pulling the proper file in my C# method, it is just not giving the file save dialog.
However, if I call this from my C# page load method with a static statusID for testing purposes, it works just fine.
Here is the C# method:
public void Get_Attachment_By_StatusID(int statusID)
{
SqlDataReader _reader = null;
string _connString = "Data Source=133.31.32.33;Initial Catalog=Reports;Integrated Security=True";
string sql = "SELECT a.StatusID ,a.DocumentName ,a.MIMETypeID ,a.Binary ,a.CreatedDate ,a.CreatedBy " +
",b.MIMEType FROM Attachments a Inner join MIME_Types b on a.MIMETypeID = b.ID " +
"WHERE [StatusID] = {0} ";
sql = string.Format(sql, statusID);
try
{
_connection = new SqlConnection(_connString);
_connection.Open();
using (SqlCommand cmd = new SqlCommand(sql, _connection))
{
cmd.CommandType = System.Data.CommandType.Text;
_reader = cmd.ExecuteReader();
if (_reader.HasRows)
{
while (_reader.Read())
{
System.Web.HttpContext.Current.Response.ClearContent();
System.Web.HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
System.Web.HttpContext.Current.Response.ContentType = _reader["MIMEType"].ToString();
System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + _reader["DocumentName"].ToString() + ";");
byte[] b = (byte[])_reader["Binary"];
System.Web.HttpContext.Current.Response.BinaryWrite(b);
System.Web.HttpContext.Current.Response.Flush();
System.Web.HttpContext.Current.Response.Close();
}
}
_reader.Close();
_connection.Close();
}
}
catch (Exception ex)
{
//Log exception to error Logging app
string err = ex.ToString();
}
finally
{
if (_connection != null)
_connection.Close();
if (_reader != null)
_reader.Close();
}
}
Here is how I am calling it from my page, in javascript:
function GetFile(statusID) {
var url = '/Home/Get_Attachment_By_StatusID';
$.ajax({
url: url,
type: 'post',
cache: false,
data: JSON.stringify({ "statusID": statusID }),
contentType: 'application/json',
success: function (data) {
}
});
}
Nothing happens. In Chrome, I don't see anything in the javascript console, and in IE, my console spits this out: "XML5619: Incorrect document syntax."
Again, if I go into the controller, and call the method in my page load method, it presents the save file dialog and saves the file just fine. So I must be doing something wrong with my javascript/jquery/ajax...
I am new to MVC4 and know I'm missing something here. What am I missing?

Use window.open('CONTROLLER_URL/STATUS_ID'); instead of an AJAX request.
<a target="_blank" href="javascript:window.open('/Home/Get_Attachment_By_StatusID/12345');">Test</a>

Here's one suggestion, largely based on answer from LastCoder:
Decorate your action with the [HttpGet] attribute and change the parameter name to id:
[HttpGet]
public void Get_Attachment_By_StatusID(int id) ...
Now in your client-side code, simply do this:
function GetFile(statusID) {
var url = '/Home/Get_Attachment_By_StatusID/'+statusID;
window.location=url;
}