src/app/services/user.service.ts

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

import { SessionContext } from '../common/session-context';
import { Globals } from '../common/globals';
import { BaseHttpService } from './base-http.service';
import { User } from '../model/user';

import { MessageService } from './message.service';

@Injectable()
export class UserService extends BaseHttpService  {

    constructor(
        private _http: Http,
        public messageService: MessageService,
        private _sessionContext: SessionContext) {
        super(messageService);        
    }

    public getUsers(): Observable<User[]> {
        const headers = new Headers();
        this.createCommonHeaders(headers, this._sessionContext);
        return this._http.get(super.getBaseUrl() + '/users', { headers: headers })
            .map(res => super.extractData(res, this._sessionContext))
             .catch(error => {        
                  return super.handleErrorPromise(error);      
                 });
    }
    
}