Angular 2: Sending an HTTP GET request with custom headers and parameters

I have been encountering difficulties while attempting to retrieve data from a Stardog triple store into Angular. Despite successfully accessing the service using curl with matching headers and parameters, I am unable to replicate this functionality within my Angular application. Even after trying variations like omitting parameters and manually entering the full URL ('localhost:5820/myDB/query?reasoning=false&query=SELECT * WHERE {?s ?p ?o}'), I haven't had any success.

private _queryUrl = 'http://localhost:5820/myDB/query';

constructor(private _http: Http) {}

getData() {
    let username : string = 'admin';
    let password : string = 'admin';

    let headers = new Headers();
    headers.append('Authorization', "Basic " + btoa(username + ":" + password));
    headers.append('Content-Type', 'application/rdf+xml');
    headers.append('Accept', 'application/sparql-results+json');

    let params = new URLSearchParams();
    params.set('reasoning', 'false');
    params.set('query', 'SELECT * WHERE {?s ?p ?o}');

    let options = new RequestOptions({ headers: headers, search: params });

    return this._http
        .get(this._queryUrl, options)
        .map((res: Response) => res.json());
}

Answer №1

Make sure to specify the correct content type when querying with SPARQL. According to the SPARQL spec, there should be no content type specified when using application/rdf+xml. For other cases, consider using either application/x-www-form-urlencoded for URL-encoded POST queries or application/sparql-query for direct POST queries.

Answer №2

All I really needed was a solid night of rest. The challenge arose when I decided to create an in-memory test API to simulate a genuine API. Surprisingly, the code above worked flawlessly! 😄

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