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Unexpected JSon response from Spring Rest API Controller

I have a method in my Spring controller, in which I am returning an object containing a spring attribute with a value "\HelloWorld". To store it into Java String object I have to put escape character, then the string becomes "\\HelloWorld". When I print, that works totally fine and prints "\HelloWorld". but when I return it in JSon response, it's returning "\\HelloWorld".
But I want it to return "\HelloWorld".
Bellow is the snippet:
#RequestMapping("")
#ResponseBody
public MyDataObject greeting() {
MyDataObject f = new MyDataObject();
f.setMessage("\\HelloWorld");
return f;
}
It's Json response is "message":"\\HelloWorld", but I want it "\HelloWorld".
Note: I don't want to unescape manually specific to that string.

You can use a library such as Jakson and it will internally handle such complexities.
MyDataObject f = new MyDataObject();
f.setMessage("\\HelloWorld");
String payload = new ObjectMapper().writeValueAsString(params);

Spring MVC - Ajax call returns JSON with Unterminated string

I'm very new to this, like really, really new.
I'm using Spring MVC (5.0) and am making an ajax call, as shown below.
This all works fine.
#RestController
public class AjaxController
{
#RequestMapping(value="/search/users", method=RequestMethod.GET)
public Person getUsers(#RequestParam("username") String username)
{
persons = personService.findPersonByUsername(username);
return persons.size() == 0 ? null : persons.get(0);
}
}
The method gets the person from the database and returns it.
According to the Spring Restful guide,
"The XXX object must be converted to JSON.Thanks to Spring’s HTTP message converter support, you don’t need to do this conversion manually. Because Jackson 2 is on the classpath, Spring’s MappingJackson2HttpMessageConverter is automatically chosen to convert the XXX instance to JSON."
So, Spring is automatically generating the JSON which will be returned to the client. The problem is, I get an error message in my client javascript:
SyntaxError: JSON.parse: unterminated string literal at line 1 column 103911 of the JSON data
My client javascript is equally simple, consisting of only:
function ajax_get_users(input_box)
{
var xhttp = new XMLHttpRequest();
xhttp.open("GET", "users?username=" + username, true); // url of server-side ajax script, specify synchronous ajax call
// get asynchronous response
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
var person = JSON.parse(this.responseText); // this is where the unterminated String error occurs
}
};
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); // set http header
xhttp.send(); // send the ajax request to the web server
}
Since Spring is constructing the JSON, how do I even fix the problem?

AngularJS $http get return null status 0

I'm trying to create $http get request to fetch some json data generated by my web service, but it returns null error. However, the $http request works fine when I use this sample url instead (it returns json string too)
This is my angular code :
angular.module('ionicApp', ['ionic'])
.controller('ListCtrl', function ($scope, $http) {
$http.defaults.headers.post["Content-Type"] = "application/x-www-form-urlencoded";
$http.get("http://localhost:8080/InventoryCtrl_Service/webresources/IVC_Service/GetUserList")
.then(function(response) {
console.log("success ");
},
function(response) {
console.log("Error : " + response.data + " Status : " + response.status);
}
});
This is my web service code :
#GET
#Path("/GetUserList")
#Produces("application/json")
public Response GetUserList() throws SQLException {
net.sf.json.JSONObject json = new net.sf.json.JSONObject();
JSONObject obj1 = new JSONObject();
JSONObject obj2 = new JSONObject();
JSONObject outerObject = new JSONObject();
JSONArray arr = new JSONArray();
obj1.put("Name", "Sara");
obj2.put("Name","David");
arr.add(obj1);
arr.add(obj2);
outerObject.put("records", arr);
return Response.status(200).entity(outerObject.toString()).build();
}
When I run the above code, it returns json string like this :
{"records":[{"Name":"Sara"},{"Name":"David"}]}
The console log returns this :
Error : null Status : 0
What is the meaning of the null error? Or is there anything wrong with how I return the json string?

Try using JSON_STRINGIFY, this will convert your incoming data into String format.
console.log(JSON_STRINGIFY(response.data));
TO verify what data your web service is returning, you can always check it by hitting your web service via postman.

I managed to solve this by adding CORS (Access-Control-Allow-Origin) to the response header, based on another SO answer. There's no problem with my angular code, it's just that I need to modify my web service code to enable the CORS. So I just modified the part where it returns data to become like this :
return Response.status(200).entity(outerObject.toString()).header("Access-Control-Allow-Origin", "*").build();

How to create a Json Object with empty strings and send it as a Web Service Response

I was querying and getting data from database using Spring jdbctemplate rowmapper. Once I get the data I was mapping it to a Java object and converting it to a json object.
My json object contains contains a object with 2 fields
code
status
When I was getting the data from database I was passing 200 and success data to the above 2 fields and passing the json object as web service response.
My actual question is even if I didn't get any data, I need to pass the json object as web service response but with code as "404" amd message field as "no data" and other fields are to be empty strings ("") , similarly if any exception occurred, need to send json object with empty strings but with 503 code.
How can I do that?
My method code snippet:
userdtls= userDaoimpl.getUserdetails(userId);
if (userdtls== null) {
ResponseBuilder builder = Response.ok(convertToJson(userdtls),MediaType.APPLICATION_JSON).status(Status.NOT_FOUND).entity("No such user " + userdtls+);
throw new WebApplicationException(builder .build());
}
convertToJson.java
public String convertToJson(UserData userdtls) {
StatusData status = new StatusData ();
status.setCode("200");
status.setMessage("Success");
userdtls.setStatus(status);
PersonalData personal = new PersonalData();
personal.setdob("june11");
personal.setage("28");
userdtls.setPersonal(personal);
Gson gson = new GsonBuilder().serializeNulls().create();
return gson.toJson(userdtls));

Empty object in browser when returning JSONObject

I have this method :
#GET
#Path("/myservice")
#Produces(MediaType.APPLICATION_JSON)
public Response mysercice() {
boolean userExists = false;
CacheControl cacheControl = new CacheControl();
cacheControl.setNoCache(true);
cacheControl.setNoStore(true);
JSONObject jsonObject = new JSONObject();
jsonObject.put("userExists", userExists);
return Response.ok(jsonObject, MediaType.APPLICATION_JSON).cacheControl(cacheControl).build();
}
When accessing to the URL of the method in the browser, I get { }, it means that the object is empty.
So, I tried to use :
return Response.ok(jsonObject.toString(), MediaType.APPLICATION_JSON).cacheControl(cacheControl).build();
So, I get in the browser {"userExists" : false}
But I didn't understand why when returning simply the JSONObject, we get in the browser an empty object.

Most JAX-RS implementations come with a provider for mapping response entities to JSON. So when you write:
return Response.ok(jsonObject, MediaType.APPLICATION_JSON).build();
You are basically requesting that the JAX-RS provider marshall the JSONObject into JSON for you. The only problem being that JSONObject isn't really meant to be serialized this way. Instead its meant to be used to build a JSON representation incrementally, then convert that representation into a JSON string value. You have two options:
Create a POJO containing all the fields you want to send back to the client. Return this POJO in your method and it will be automatically converted to JSON (`return Response.ok(myPojo, MediaType.APPLICATION_JSON).build()
Return the JSON data directly as a String (which you already did in your example that works).