Sending array of objects via POST not working - Angular

Question

I cannot send an array of FormGroup objects to my backend.

Error: It says: "Unsupported Media Type" "Content type 'text/plain;charset=UTF-8' not supported" error 415.

Previously, it could not deserialize the array into my Java object in my backend because it was not in JSON format, and now I am stuck with this.

I have tried to use JSON.stringify(arrayOfFormGroups) to convert it to JSON, but I do not know why it says I am sending plain/text.

This code gives you the content type error.

TS

// Inserts all the form data into one array
let dataArray: String[] = [this.form1.value, this.form2.value, this.form3.value, this.form4.value];

// Send the form data to the service, which then sends the data to the server (Spring-Boot)
this.data.sendFormData(JSON.stringify(dataArray)).subscribe(
      response => console.log("Success! ", response),
      error => console.error("Error: ", error)
    );
}

This code makes the array undeserializable for consumption in the backend.

TS

// Inserts all the form data into one array
let dataArray: String[] = [this.form1.value, this.form2.value, this.form3.value, this.form4.value];

// Send the form data to the service, which then sends the data to the server (Spring-Boot)
this.data.sendFormData(dataArray).subscribe(
      response => console.log("Success! ", response),
      error => console.error("Error: ", error)
    );
}

Service

sendFormData(userData) {
   return this.http.post<any>("http://localhost:8080/create", userData);
}

Expected

I want to POST my array of FormGroups to my backend as JSON String.

Actual

An error occurs when I POST, unsupported content-type plain/text even though I am sending JSON.

You shouldn't stringify it, that's why Angular thinks it's plain text. It's unclear what the deserialisation problem was, did you check whether the payload was as expected? — jonrsharpe
– jonrsharpe, Commented Jul 13, 2019 at 21:59
It could not deserialize it because it was not in JSON format. — Compiler v2
– Compiler v2, Commented Jul 13, 2019 at 22:01
When? Before you started stringifying it? What was being sent? — jonrsharpe
– jonrsharpe, Commented Jul 13, 2019 at 22:03
Yes, before I was stringifying it. I cannot send the array just as it is or it gives me an error. — Compiler v2
– Compiler v2, Commented Jul 13, 2019 at 22:03
And how do you expect that to help? What actually gets sent? What payload, what content type? And what exactly happens in the backend? What does the backend even look like? What's the right payload? Have you sent it successfully with a different client (e.g. Postman)? It's not even clear you're looking at the right side of the problem right now. — jonrsharpe
– jonrsharpe, Commented Jul 13, 2019 at 22:10

Compiler v2 · Accepted Answer · 2019-07-17 18:59:41Z

The solution is to store the data into an object, not an array. The reason is that you cannot send a JSON array to your backend if it only consumes one single object. They are incompatible.

TS

 // User object
  private user = {
    firstName: String,
    lastName: String
 };

....

// Populates the user object
this.user.firstName = this.form1.controls['firstName'].value;
this.user.lastName = this.form2.controls['lastName'].value;

// Sends the form data to the service
this.data.sendFormData(JSON.stringify(this.user)).subscribe(
   response => console.log("Success! ", response),
   error => console.error("Error: ", error)
);

I am using multiple form groups because I am using Angular material's stepper in linear mode, which requires each step to have its own FormGroup.

More on that: https://material.angular.io/components/stepper/overview#linear-stepper

Also, I had to add a header to my POST:

My Service

private header = new HttpHeaders({ 'content-type': 'application/json' });

constructor(private http: HttpClient) { }

ngOnInit() { }

sendFormData(userData) {
  return this.http.post("http://localhost:8080/createAccount", userData, { headers: this.header });
}

Good reading on converting objects to JSON VS arrays to JSON: https://alligator.io/js/json-parse-stringify/

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