无法从 Angular 调用 REST API 到 Spring REST 控制器

Question

I'm trying to make a rest call to my spring controller, it works when I put the URL in browser and able to see the JSON response. But, when I try the same by integrating into the Angular code, it doesn't throw any exception either in browser console or server console.

Here is my code.

Imports

import { Component, OnInit  } from '@angular/core';
import { Http, Response  } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';

class Result {
statusCode : number;
errorMsg: string;
result: string;

}


@Component({
selector: 'app-root',
templateUrl: './app.component.html',
 styleUrls: ['./app.component.css'],

 })
 export class AppComponent {
 ngOnInit() {
   this.getEmployees();
 }

public getEmployees(): Observable<Result[]> {

   return this.http
    .get(this.API_URL + '/employees')
    .map(response => {
     const todos = response.json();
     console.log(todos);
     return "";
})
.catch(this.handleError);
}

private handleError (error: Response | any) {
  console.error('ApiService::handleError', error);
  return Observable.throw(error);
}

And here is my spring code

  @RequestMapping(value ="/employees", method = RequestMethod.GET)
public ResultDto getEmployees(HttpServletRequest req) {
    ResultDto result = null;
    try {
        ServletContext ctx = req.getServletContext();
        @SuppressWarnings("unchecked")
        Map<String,String> users = (Map<String, String>) ctx.getAttribute("userRoles");
        result = new ResultDto();
        result.setStatusCode(EmapConstants.SUCCESS);
        result.setResult(users);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return result;
}

My ResultDto class is having three properties

private int statusCode;
private String errorMsg;
private Object result;

Any ideas why its not hitting the method?

Answer 1

Assuming you are using the HttpClient from @angular/common/http :

If you use the HttpClient you can either add a type to the http.get() which is your expected response json. Using this you only get the response body as your result. You could also add the option observe: 'response' to your get request in order to get the actual response back.

You would probably only want to use the latter if you need other information than the body eg the response status. If you only need the body your request could look something like this:

constructor(private httpClient: HttpClient) {}

getEmployees() Observable<Result[]>{
    return this.httpClient
        .get<Result[]> (this.API_URL + '/employees', {params: _params})
        .pipe(catchError(() => this.handleError()));

}

Yeah and you always have to subscribe to the observable that's right. As mentioned in the comments as well.