angular2-jwt provides an AuthHttp wrapper for the native Angular http class that automatically includes the http authorization header with each request. In my services I am usually calling a backend api like this
getThings(): Observable<Thing[]> {
return this.http.get(environment.apiEndpoint + '/things')
.map(res => res.json().data)
.catch(res => this.handleError(res));
}
with an error handler like
private handleError(error: Response | any) {
let errMsg: string;
if (error instanceof Response) {
const body = error.json() || '';
const err = body.error || JSON.stringify(body);
errMsg = `${error.status} - ${error.statusText || ''} ${err}`;
} else {
errMsg = error.message ? error.message : error.toString();
}
// If JWT is expired open a new window to log in again
if (errMsg.indexOf('No JWT present or has expired') !== -1) {
window.open(environment.apiEndpoint + '/loginToApp?expired', '_blank', 'height=570,width=520');
}
console.error(error);
return Observable.throw(errMsg);
}
I keep repeating the handleError method in all my services and I would like to know if there is a way to make this DRY. Is there a way to define a generic error handler for all http requests?
I'd like to avoid having to call catch each time if possible. Is there a way to extend the http class to automatically catch errors on each request and then in special situations I can add custom catch logic on a case by case basis?
I could export the method from another file and import it in each of my services but I think there has got to be a better way. Thanks for any suggestions.
UPDATE: I ended up extending the AuthHttp class from angular2-jwt.
import { Http, RequestOptions, Response, Request, RequestOptionsArgs } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';
import { AuthHttp, AuthConfig } from 'angular2-jwt';
export class ApiHttp extends AuthHttp {
public request(url: string | Request, options?: RequestOptionsArgs): Observable<Response> {
return super.request(url, options).catch(res => this.handleError(res));
}
private handleError(error: Response | any) {
// error handling then rethrow the error
return Observable.throw(error);
}
}
You can create custom service CustomAuthHttp like AuthHTTP Wrapper. Like wrapper adds header, in CustomAuthHttp you can catch error. Then in your code inject CustomAuthHttp instead of AuthHTTP and use.
@Injectable()
export class CustomAuthHttp {
constructor(private http: AuthHttpWrapper) { }
get(url: string) {
return this.http.get(url)
.catch(res => this.handleError(res));
}
private handleError(error: Response | any) {
// your code
return Observable.throw('');
}
}