Tips for resolving the problem when encountering the "undefined data" issue in the success callback of an AJAX request

Question

Tips for resolving the problem when encountering the "undefined data" issue in the success callback of an AJAX request

I am facing an issue with my JSP page where I have a button that calls an Ajax method named "sendmail()" upon click. The send mail API is in the Controller, and I am trying to display an alert message in the Ajax success function using data.message, but it shows that data is undefined.

I attempted to set the response object in the controller with a message string as 'success' and return it as a string. Please note that to achieve this, I had to change the return type of my controller's sendmail method to String. However, I noticed that the Ajax call does not enter the success function in this scenario. It works fine when the method has a void return type. Upon checking with the Chrome Developer tools, the network call returns a 404 error (not found). The email is sent successfully, but the Ajax success function is not triggered.

Below is the code snippet for the button and Ajax method:

<div class="uk-width-large-2-5">

  <div class="uk-form-row">
  <label>Message</label>
  <textarea id="message" cols="30" rows="4" class="md-input"></textarea>
  </div>
  <div class="uk-form-row">
  <button type="submit" class="md-btn md-btn-success md-btn-large" onclick="sendMail()">Send Message</button>
 </div>
 </div>

Ajax method :

<script>
function sendMail() {
 var reqJson = {};
 reqJson.msg = $("#message").val();


$.ajax({
type : "POST",
url : "sendMail",
data : JSON.stringify(reqJson),
dataType: 'json',
contentType: "application/json",
  success : function(data) {    
  console.log("data :"+data.message);
               }
 error: function()
 {
}
    });                                 
}
</script>

Maincontroller.java

 @RequestMapping(value = "/sendMail", method = RequestMethod.POST, produces = "application/json")
   public void sendContact(HttpServletRequest request, HttpServletResponse response, @RequestBody String payload) {
        JSONObject jRespObj = new JSONObject();

      try {
        System.out.println("Welcome");
        JSONObject jPayload = new JSONObject(payload);
         System.out.println("jobj : "+jPayload);
         String message = jPayload.getString("msg");
         InputStream inputStream = UserController.class.getResourceAsStream("/Contactusrequest.htm");
      StringWriter writer = new StringWriter();
      try {
          IOUtils.copy(inputStream, writer);
         } catch (IOException e) {
          e.printStackTrace();
         }
      HttpSession session = request.getSession(true);

        String from = (String) session.getAttribute("email");
        String to ="<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="1068696a507172733e737f7d">[email protected]</a>";
        String emailContent = writer.toString();
        emailContent = emailContent.replace("replaceMeFromEmail",from);
        emailContent = emailContent.replace("replaceMeToEmail", to);
        emailContent = emailContent.replace("replaceMeReason", message);

         emailClient.sendMail("", to, null, "Contact Us Request", emailContent);
        jRespObj.put("message", "Mail sent successfully");
        response.setStatus(HttpServletResponse.SC_OK);

     } catch (Exception ex) {
          ex.printStackTrace();
        response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
     }
    return jRespObj.toString();
   }

I am looking to receive the response object from the controller in the Ajax success callback to access the data.message.

javascript ajax jsp controller form-submit

Answer 1

Answer №1

Solution 1. When working with Ajax, be cautious of undefined errors when returning the response. To avoid this issue, consider writing the JSON response in the body using Gson or JSONObject instead of simply returning it.

For example.

//Write the json response in body
  //return jRespObj.toString();
  response.getWriter().write(jRespObj.toString());

Solution 2 - Eliminate all other System.out.println statements and present a single response in JSON format like so:

System.out.print(jRespObj.toString());

When working with Ajax, you can retrieve the response using the following code snippet:

$ajax({
----
success : function(data) {    
  console.log("data :"+data['message']);
},
 error: function()
 {
}

Answer 2

Solution 1. When working with Ajax, be cautious of undefined errors when returning the response. To avoid this issue, consider writing the JSON response in the body using Gson or JSONObject instead of simply returning it.

For example.

//Write the json response in body
  //return jRespObj.toString();
  response.getWriter().write(jRespObj.toString());

Solution 2 - Eliminate all other System.out.println statements and present a single response in JSON format like so:

System.out.print(jRespObj.toString());

When working with Ajax, you can retrieve the response using the following code snippet:

$ajax({
----
success : function(data) {    
  console.log("data :"+data['message']);
},
 error: function()
 {
}

Answer 3

Answer №2

After much trial and error, I finally discovered the solution: By adding @Responsebody and parsing the data received in Ajax success, I was able to make everything work smoothly. Here is the code snippet:

@RequestMapping(value = "/sendMessage", method = RequestMethod.POST)
@ResponseBody
public String sendMessage(HttpServletRequest request, HttpServletResponse response, @RequestBody String payload) throws JSONException, IOException {
    JSONObject jRespObj = new JSONObject();

    try {
        System.out.println("Welcome");
        JSONObject jPayload = new JSONObject(payload);
        System.out.println("jobj : " + jPayload);
        String message = jPayload.getString("message");

        InputStream inputStream = UserController.class.getResourceAsStream("/Contactusrequest.htm");
        StringWriter writer = new StringWriter();
        
        try {
            IOUtils.copy(inputStream, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }

        HttpSession session = request.getSession(true);
        String from = (String) session.getAttribute("email");
        String to ="<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="760e0f0c36131a1315020419181905191a03021f1918055815191b">[email protected]</a>";
        
        String emailContent = writer.toString();
        emailContent = emailContent.replace("replaceMeFromEmail",from);
        emailContent = emailContent.replace("replaceMeToEmail", to);
        emailContent = emailContent.replace("replaceMeReason", message);
        
        emailClient.sendMail("", to, null, "Contact Us Request", emailContent);
        jRespObj.put("message", "Mail sent successfully");

    } catch (Exception ex) {
        ex.printStackTrace();
    }
    
    return jRespObj.toString();
}

Ajax process:

<script>
function sendMessage() {
    console.log("page load");

    var reqJson = {};
    reqJson.message = $("#message").val();
    
     $.ajax(
     {
         url : "sendMessage/",
         type: "POST",
         data : JSON.stringify(reqJson),
         contentType: "application/json",
         success:function(data)
         {
            var msg = JSON.parse(data);
            console.log(msg);

            UIkit.notify('<a href="#" class="notify-action">Clear</a> ' + msg.message, {
             pos : 'top-center',
             status:'success',
             timeout : 2000
           });

          setTimeout(function(){ location.reload(); }, 2000);
         }, 
         error: function(data)
         {

           UIkit.notify('<a href="#" class="notify-action">Clear</a> ' + "Mail not sent", {
             pos : 'top-center',
             status:'warning',
             timeout : 6000
           }); 
         }
       });

    }
 </script>

Answer 4

After much trial and error, I finally discovered the solution: By adding @Responsebody and parsing the data received in Ajax success, I was able to make everything work smoothly. Here is the code snippet:

@RequestMapping(value = "/sendMessage", method = RequestMethod.POST)
@ResponseBody
public String sendMessage(HttpServletRequest request, HttpServletResponse response, @RequestBody String payload) throws JSONException, IOException {
    JSONObject jRespObj = new JSONObject();

    try {
        System.out.println("Welcome");
        JSONObject jPayload = new JSONObject(payload);
        System.out.println("jobj : " + jPayload);
        String message = jPayload.getString("message");

        InputStream inputStream = UserController.class.getResourceAsStream("/Contactusrequest.htm");
        StringWriter writer = new StringWriter();
        
        try {
            IOUtils.copy(inputStream, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }

        HttpSession session = request.getSession(true);
        String from = (String) session.getAttribute("email");
        String to ="<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="760e0f0c36131a1315020419181905191a03021f1918055815191b">[email protected]</a>";
        
        String emailContent = writer.toString();
        emailContent = emailContent.replace("replaceMeFromEmail",from);
        emailContent = emailContent.replace("replaceMeToEmail", to);
        emailContent = emailContent.replace("replaceMeReason", message);
        
        emailClient.sendMail("", to, null, "Contact Us Request", emailContent);
        jRespObj.put("message", "Mail sent successfully");

    } catch (Exception ex) {
        ex.printStackTrace();
    }
    
    return jRespObj.toString();
}

Ajax process:

<script>
function sendMessage() {
    console.log("page load");

    var reqJson = {};
    reqJson.message = $("#message").val();
    
     $.ajax(
     {
         url : "sendMessage/",
         type: "POST",
         data : JSON.stringify(reqJson),
         contentType: "application/json",
         success:function(data)
         {
            var msg = JSON.parse(data);
            console.log(msg);

            UIkit.notify('<a href="#" class="notify-action">Clear</a> ' + msg.message, {
             pos : 'top-center',
             status:'success',
             timeout : 2000
           });

          setTimeout(function(){ location.reload(); }, 2000);
         }, 
         error: function(data)
         {

           UIkit.notify('<a href="#" class="notify-action">Clear</a> ' + "Mail not sent", {
             pos : 'top-center',
             status:'warning',
             timeout : 6000
           }); 
         }
       });

    }
 </script>

Tips for resolving the problem when encountering the "undefined data" issue in the success callback of an AJAX request

Answer №1

Answer №2

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