How can I receive just a string in Angular frontend from REST-Backend

Question

For my application I calculate some Value in my Java backend. The only thing I want to do is to receive this String in my Angular frontend, however I struggle with the Observable type.

This is my backend REST Call it uses Spring Boot/Jersey annotations:

@GET
@Path("/calculate/{auftragId}")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public String calculateAwWithJSON(@PathParam("auftragId") String auftragId) {
    restLog("receiving put request /put/auftragId ->> " + auftragId);
    for (AuftragREST anAuftragRepoList : auftragRepoList) {
        if (anAuftragRepoList.getId().replace(" ", "").equals(auftragId)) {
            restLog("successfully calculated AW the requested data!");
            return ObjektprotokollCalculator.calculateAW(anAuftragRepoList).toString();
        }
    }
    return "0";
}

Now the only thing I want to do is get that string in my Angular frontend. However I do not understand how this works with Observables, here is what I have:

public getFromHttpClient(url: string, json: any): Observable<string> {
    return this.httpClient.get<string>(`${this.basePath}/${url}/${json.id}`);
}

However when I try to assing this it doesn't work:

let m: string = this.getFromHttpClient("auftrag/calculate", this.myObject).subscribe();

What's the easiest way to do this? What am I doing wrong? I couldn't find a similar example, everyone always just shows how to do it with Arrays and such but none show how it's done for just a single string.

Karim · Accepted Answer · 2019-04-04 13:56:49Z

2

This is the proper syntax to do it:

this.getFromHttpClient("auftrag/calculate", this.myObject).subscribe((response) => let m: string = response;);

edited Apr 4, 2019 at 13:56

answered Apr 4, 2019 at 13:13

Karim

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7 Comments

Miger Over a year ago

thanks, but still I get this error error TS2322: Type 'Subscription' is not assignable to type 'string'.

Karim Over a year ago

@Miger Where did you call the .subscribe method ?

Miger Over a year ago

I do this:

let m: string = this.myService.getFromHttpClient("auftrag/calculate", this.myObject()).subscribe(response => { return response });

Karim Over a year ago

Yes but where is this line called ?

Miger Over a year ago

Yea, you made it wrong.. it has to be inside the subscription like this:

this.myService.getFromHttpClient("auftrag/calculate", this.myObject()).subscribe(response => { let m: string = response });

|

BeWu · Accepted Answer · 2019-04-04 13:16:01Z

0

You need to add a function to the subscribe:

let m: string;
this.getFromHttpClient("auftrag/calculate", this.myObject).subscribe((result: string) => {m = result;});

edited Apr 4, 2019 at 13:16

answered Apr 4, 2019 at 13:03

BeWu

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1 Comment

Miger Over a year ago

thanks, but still I get this error error TS2322: Type 'Subscription' is not assignable to type 'string'.

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