Call from angular frontend to java backend fails without error

Question

I'm building a project in angular which connects to my java-backend (restapi). The project basics are already done, but now I'm adding one by one some advanced calls. Suddenly, I come to the point where I'm implementing a new method, but therequest just doesn't reach the method in the controller. I don't even get an error in the frontend, the backend just doesn't react. The frontend service creates the right url, makes the call, no error.. backend receives nothing.

I tried changing the request to get, losing the pathvariables and using RequestBody, creating a simple test-controller that returns a String, .. nothing seems to work anymore, except what was already their. What am I doing wrong? Why doesn't this specific request doesn't reach my backend?

angular service:

const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type':  'application/json'
  })
};

@Injectable({
  providedIn: 'root'
})

export class ProductService {
url = "http://localhost:8080/products/";

  constructor(private http: HttpClient) { }

  extendDateWithMonths(month : number, id:number | undefined): Observable<Response> {
    console.log("service reached");
    console.log("month: " + month);
    console.log("id: " + id);
    const specificUrl = this.url + "extenddate/"+ `${month}` +"/"+ `${id}`;
    console.log("url: " + specificUrl);
    return this.http.post<any>(specificUrl, month, httpOptions);
   
  }
}

console.out request:

• service reached
• month: 3
• id: 1
• url:http://localhost:8080/products/extenddate/3/1

java backend controller running on localhost 8080:

@RestController
@RequestMapping("/products")
@CrossOrigin(exposedHeaders = "http://localhost:4200")
public class ProductController {

    @Autowired
    ProductService productService;

    @PostMapping("/extenddate/{month}/{id}")
    public ResponseEntity<?> extenddate(@PathVariable int month, @PathVariable long id){
        System.out.println("extenddate reached");
        productService.extendProductsFromBon(month, id);
        return ResponseEntity.ok(new MessageResponse("date extended successfully!"));
    }
}

Why doesn't this specific request doesn't reach my backend? Why don't I get an error or anything from the console? Either it can reach the restapi or it cannot, but this is very strange.

Answer 1

You call the method, that is why you see the console logs. The return value, however is a cold observable. In order to actually send the request to the backend you need to subscribe to the observable.

I expect that you simply call the method like this somewhere:

const response = this.productService.extendDateWithMonths(1, 2);

What you need to do:

this.productService.extendDateWithMonths(1, 2).subscribe(
  response => this.response = response;
);