Why is spring returning me an empty llist?

I dont seem to know why Spring is returning me an empty list enough I have passed in a JSON.stringify() string from reactJS

This is my code for reactJS

postData(item){
console.log(item)
fetch("http://localhost:8080/addSuspect", {
"method": "POST",
"headers": {
"content-type": "application/json"
},
"body": item
})
.then(response => {
console.log(response);
})
.catch(err => {
console.log(err);
});
}
uploadFile(event) {
let file
let file2
//Check if the movements andsuspected case profiles are uploaded
if(event.target.files.length !== 2){
this.setState({error:true, errorMsg:"You need to upload at least 2 files!"})
return
}
//Check if the file is the correct file
console.log("Files:")
for (var i=0, l=event.target.files.length; i<l; i++) {
console.log(event.target.files[i].name);
if (event.target.files[i].name.includes("_suspected")){
file = event.target.files[i]
}
else if (event.target.files[i].name.includes("_movements")){
file2 = event.target.files[i]
}
else{
this.setState({error:true, errorMsg:"You have uploaded invalid files! Please rename the files to <filename>_suspected (For suspected cases) or <filename>_movement (For suspected case movement)"})
return
}
}
//Reads the first file (Suspected profile)
if (file) {
const reader = new FileReader();
reader.onload = () => {
// Use reader.result
const lols = Papa.parse(reader.result, {header: true, skipEmptyLines: true}, )
console.log(lols.data)
// Posting csv data into db
// this.postData('"' + JSON.stringify(lols.data) + '"')
this.postData(JSON.stringify(lols.data))
// Adds names into dropdown
this.setState({dataList: ["None", ...lols.data.map(names => names.firstName + " " + names.lastName)]})
const data = lols.data
this.setState({suspectCases: data})
}
reader.readAsText(file)
}
}

Here is what I get from console.log():

>[{"id":"5","firstName":"Bernadene","lastName":"Earey","email":"bearey4@huffingtonpost.com","gender":"Female","homeLongtitude":"","homeLatitude":"","homeShortaddress":"","homePostalcode":"552209","maritalStatus":"M","phoneNumber":"92568768","company":"Yadel","companyLongtitude":"","companyLatitude":""},{"id":"14","firstName":"Mada","lastName":"Lafaye","email":"mlafayed@gravatar.com","gender":"Female","homeLongtitude":"","homeLatitude":"","homeShortaddress":"","homePostalcode":"447136","maritalStatus":"M","phoneNumber":"85769345","company":"Eare","companyLongtitude":"","companyLatitude":""}]

Below shows the Code in my Spring Controller

@RestController
public class HomeController {
private final profileMapper profileMapper;
private final suspectedMapper suspectedMapper;
public HomeController(@Autowired profileMapper profileMapper, @Autowired suspectedMapper suspectedMapper) {
this.profileMapper = profileMapper;
this.suspectedMapper = suspectedMapper;
}
@GetMapping("/listAllPeopleProfiles")
//Removes the CORS error
@CrossOrigin(origins = "http://localhost:3000")
private Iterable<Peopleprofile> getAllPeopleProfiles (){
return profileMapper.findAllPeopleProfile();
}
@GetMapping("/listAllSuspectedCases")
@CrossOrigin(origins = "http://localhost:3000")
private Iterable<Suspected> getAllSuspected(){
return suspectedMapper.findallSuspected();
}
@PostMapping("/addSuspect")
@CrossOrigin(origins = "http://localhost:3000")
private void newSuspectedcases(ArrayList<Suspected> unformattedcases){
//        try {
//            final JSONObject obj = new JSONObject(unformattedcases);
//
//            System.out.println(obj);
////            ObjectMapper mapper = new ObjectMapper();
////            List<Suspected> value = mapper.writeValue(obj, Suspected.class);
//        } catch (JSONException e) {
//            e.printStackTrace();
//        }
//
//        Gson gson = new Gson();
//        List<Suspected> suspectedCases = gson.fromJson(unformattedcases, new TypeToken<List<Suspected>>(){}.getType());
System.out.println(unformattedcases);
//        for (Suspected suspected : suspectedCases){
//            suspectedMapper.addSuspectedCase(suspected);
//        }
}
}

I am not sure I understand your issue. This is my best guess about what you meant and what you want to happen :

• You want your controller to receive ArrayList < Suspected > as the POST request body
• You want your controller to return ArrayList < Suspected > as the POST response body

If that's the case, try this :

[...]
@PostMapping("/addSuspect")
@CrossOrigin(origins = "http://localhost:3000")
@ResponseBody
private ArrayList<Suspected> newSuspectedcases(@RequestBody ArrayList<Suspected> unformattedcases){
[...]
System.out.println(unformattedcases);
[...]
return unformattedcases;
}

If it's not what you meant, please provide more information.

Firstly, your controller method is returning void and not, if I undestand correctly, the payload that you're trying to send. You have to make your controller method return List<Suspected> to receive a body in the response.

Another issue is that you're missing a @RequestBody annotation on the param, which tells Spring to get the body from the request and try to deserialize it to a ArrayList of Suspects.

Another thing to note, it is a good practice to use interfaces instead of implementation classes as parameters and return value in your methods. Consider using List<Suspected> instead of ArrayList<Suspected>

So the final method should look like this:

   @PostMapping("/addSuspect")
@CrossOrigin(origins = "http://localhost:3000")
private List<Suspected> newSuspectedcases(@RequestBody List<Suspected> unformattedcases){
[...]
System.out.println(unformattedcases);
[...]
return unformattedcases;
}

PS For CORS issues you may want to using a local proxy setup as described in React docs: https://create-react-app.dev/docs/proxying-api-requests-in-development/ And configure CORS for remote environments, without adding localhost:3000.