So I am trying to load the data from a REST source into my Angular 6 app using http: HttpClient from '@angular/common/http'. Calling the app in the browser using ng serve --open though doesn't do the job. I assume CORS to be the problem here. I guess I either have to set the server or the client headers with Access-Control-Allow-Origin or something, but I have already tried multiple ways without any success in making this simple REST call work. So what follows below is what I coded.
Calling the Angular app in the browser responds the following error:
Failed to load http://localhost:8080/mysite-backend/rest/report/single/d83badf3:
Response to preflight request doesn't pass access control check:
No 'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'http://localhost:4200' is therefore not allowed
access.
Calling the same URL (http://localhost:8080/mysite-backend/rest/report/single/d83badf3) within the Chrome browser works perfectly though:
{"id":"d83badf3","language":"en","categoryId":"a5","title":"Simcity","created":1527723183880,"modified":1527723183880}
Within Angular 6 I use the following service class that I generated with ng generate service tour. Within that I created the method getTour(id: string) which does non more than call REST at the URL and return the retrieved JSON-string as a Tour object:
import { Injectable } from '@angular/core';
import { HttpHeaders, HttpClient } from '@angular/common/http';
import { Observable, of } from 'rxjs';
import { Tour } from './tour';
import { catchError, tap } from 'rxjs/operators';
const httpOptions = {
headers: new HttpHeaders({
'Content-Type': 'application/json'
})
};
@Injectable({
providedIn: 'root'
})
export class TourService {
// URL to the web api.
private tourUrl = 'http://localhost:8080/mysite-backend/rest/report';
constructor(
private http: HttpClient
) { }
/**
*
* @param id: string GET tour report by id. Will 404 if id not found.
*/
getTour(id: string): Observable<Tour> {
httpOptions.headers.append('Access-Control-Allow-Origin', 'http://localhost:8080');
httpOptions.headers.append('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
httpOptions.headers.append('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
httpOptions.headers.append('Access-Control-Allow-Credentials', 'true');
const url = `${this.tourUrl}/single/${id}`;
console.log("XXX URL GET " + url)
return this.http.get<Tour>(url, httpOptions).pipe(
tap(_ => this.log(`fetched tour id=${id}`)),
catchError(this.handleError<Tour>(`getHero id=${id}`))
);
}
private handleError<T> (operation = 'operation', result?: T) {
return (error, any): Observable<T> => {
console.error(error);
this.log(`${operation} failed: ${error.message}`);
return of(result as T);
};
}
private log(message: string) {
console.log("Log message: " + message);
}
}
This is the Tour object:
export class Tour {
id: string;
language: string;
categoryId: string;
created: Date;
modified: Date;
title: string;
content: string;
}
I also added HttpClientModule from '@angular/common/http' to the imports array and the providers array within app.module.ts.
The RESTful WebService is built in Java. Here I have the getReport(@PathParam("reportId") String reportId) method, that gets an Report object and returns it within a Reponse:
import java.util.List;
import javax.inject.Inject;
import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
/**
* Describes the RESTful access for reports.
*/
@Path("/report")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class ReportResource {
@Inject
private Logger logger;
@GET
@Path("/single/{reportId}")
public Response getReport(@PathParam("reportId") String reportId) {
//return Mock.getReport(reportId);
return Response.ok() // 200
.entity(Mock.getReport(reportId))
.header("Access-Control-Allow-Origin", "*")
.header("Access-Control-Allow-Methods", "GET, POST, DELETE, PUT")
.allow("OPTIONS").build();
}
...
}
What must I do to make a successful call from the Angular 6 client to the Java RESTful WebService?
