javascript - How to force Angular2 to POST using x-www-form-urlencoded

Question

I have a project that needs to use Angular2 (final) to post to an old, legacy Tomcat 7 server providing a somewhat REST-ish API using .jsp pages.

This worked fine when the project was just a simple JQuery app performing AJAX requests. However, the scope of the project has grown such that it will need to be rewritten using a more modern framework. Angular2 looks fantastic for the job, with one exception: It refuses to perform POST requests using anything option but as form-data, which the API doesn't extract. The API expects everything to be urlencoded, relying on Java's request.getParameter("param") syntax to extract individual fields.

This is a snipped from my user.service.ts:

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

@Injectable()
export class UserService {
    private loggedIn = false;
    private loginUrl = 'http://localhost:8080/mpadmin/api/login.jsp';
    private headers = new Headers({'Content-Type': 'application/x-www-form-urlencoded'});

    constructor(private http: Http) {}

    login(username, password) {
        return this.http.post(this.loginUrl, {'username': username, 'password':  password}, this.headers)
            .map((response: Response) => {
                let user = response.json();
                if (user) {
                    localStorage.setItem('currentUser', JSON.stringify(user));
                }
            }
        );
    }
}

No matter what I set the header content type to be, it always ends up arriving as non-encoded form-data. It's not honoring the header I'm setting.

Has anyone else encountered this? How do you go about forcing Angular2 to POST data in a format that can be read by an old Java API using request.getParameter("param")?

Edit: For anyone else who finds this in the future, the solution is actually really simple. Set the body of the post like this:

let body = `username=${username}&password=${password}`;`

See Brad's example below.

Answer 1

For Angular 4.3+/5+ (New HTTPClient) use the following:

let body = new URLSearchParams();
body.set('user', username);
body.set('password', password);

let options = {
    headers: new HttpHeaders().set('Content-Type', 'application/x-www-form-urlencoded')
};

this.http
    .post('//yourUrl.com/login', body.toString(), options)
    .subscribe(response => {
        //...
    });

Note 3 things to make it work as expected:

1. Use URLSearchParams for your body
2. Convert body to string
3. Set the header's content-type

Attention: Older browsers do need a polyfill! I used: npm i url-search-params-polyfill --save and then added to polyfills.ts: import 'url-search-params-polyfill';