update to rxJS

Author: linux-china

src/main/frontend/src/app/service/user.service.ts

@@ -1,13 +1,14 @@
 import {Injectable} from "@angular/core";
 import {HttpClient} from "@angular/common/http";
+import {Observable} from "rxjs/Observable";
 
 @Injectable()
 export class UserService {
 
     constructor(private httpClient: HttpClient) {
     }
 
-    findById(id: number): string {
-        return "nick"
+    findById(id: number): Observable<Object> {
+        return this.httpClient.get('/json');
     }
 }