Using Http Rest APIs with Angular 2

Using http rest apis with angular 2

Well good answer provided by @langley but I would like to add some more points so posting as an answer.

First of all for consuming Rest APIs we need the Http and HTTP_PROVIDERS modules to be imported. As we are talking about Http the very first step is obviously.

<script src="node_modules/angular2/bundles/http.dev.js"></script>

But yes it is a good practice to provide HTTP_PROVIDERS in the bootstrap file because by using this way it is provided on a global level and is available to the whole project like this.

bootstrap(App, [
HTTP_PROVIDERS, some_more_dependencies
]);

and the imports to be included are....

import {Http, Response, RequestOptions, Headers, Request, RequestMethod} from 'angular2/http';

Sometimes we need to provide Headers while consuming API's for sending access_token and many more things which is done this way:

this.headers = new Headers();
this.headers.append("Content-Type", 'application/json');
this.headers.append("Authorization", 'Bearer ' + localStorage.getItem('id_token'))

Now to RequestMethods: bascially we use GET, POST but there are some more options you can refer here...

We can use requestmethods as RequestMethod.method_name

There are some more options for the APIs but for now I have posted one example for POST request which will help you by using some important methods:

PostRequest(url,data) {
this.headers = new Headers();
this.headers.append("Content-Type", 'application/json');
this.headers.append("Authorization", 'Bearer ' + localStorage.getItem('id_token'))

this.requestoptions = new RequestOptions({
method: RequestMethod.Post,
url: url,
headers: this.headers,
body: JSON.stringify(data)
})

return this.http.request(new Request(this.requestoptions))
.map((res: Response) => {
if (res) {
return [{ status: res.status, json: res.json() }]
}
});
}

you can refer here too for more info.

see also -

  • How to deal with http status codes other than 200 in Angular 2.

Update

import has been changed from

import {Http, Response, RequestOptions, Headers, Request, RequestMethod} from 'angular2/http';

to

import {Http, Response, RequestOptions, Headers, Request, RequestMethod} from '@angular/http';

Angular2 HttpClient to consume Rest API

I got the solution.

@AJT_82 gave me the main clue.

As It was said in the app module (app.module.js) file, my app was taking the data from an InMemory storage system.

When I commented this line:

//InMemoryWebApiModule.forRoot(InMemoryDataService)

it just started to get the data from the URL provided to the localhost:8080/heroes Rest API.

Sorry for making you waste your time.

How to call an rest api while bootstrapping angular 2 app

You can use APP_INITIALIZER to call a service method at bootstrap. You will require to define a provider for it in your AppModule.

Here is an example of how to do this.

StartupService (startup.service.ts)

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';

import 'rxjs/add/operator/map';
import 'rxjs/add/operator/toPromise';

@Injectable()
export class StartupService {

private _startupData: any;

constructor(private http: Http) { }

// This is the method you want to call at bootstrap
// Important: It should return a Promise
load(): Promise<any> {

this._startupData = null;

return this.http
.get('REST_API_URL')
.map((res: Response) => res.json())
.toPromise()
.then((data: any) => this._startupData = data)
.catch((err: any) => Promise.resolve());
}

get startupData(): any {
return this._startupData;
}
}

AppModule (app.module.ts)

import { BrowserModule } from '@angular/platform-browser';
import { NgModule, APP_INITIALIZER } from '@angular/core';

import { StartupService } from './startup.service';

// ...
// Other imports that you may require
// ...

export function startupServiceFactory(startupService: StartupService): Function {
return () => startupService.load();
}

@NgModule({
declarations: [
AppComponent,
// ...
// Other components & directives
],
imports: [
BrowserModule,
// ..
// Other modules
],
providers: [
StartupService,
{
// Provider for APP_INITIALIZER
provide: APP_INITIALIZER,
useFactory: startupServiceFactory,
deps: [StartupService],
multi: true
}
],
bootstrap: [AppComponent]
})
export class AppModule { }

EDIT (How to handle startup service failure):

AppComponent (app.component.ts)

import { Component, OnInit } from '@angular/core';
import { Router } from '@angular/router';

import { StartupService } from './startup.service';

@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.scss']
})
export class AppComponent implements OnInit {

constructor(private router: Router, private startup: StartupService ) { }

ngOnInit() {

// If there is no startup data received (maybe an error!)
// navigate to error route
if (!this.startup.startupData) {
this.router.navigate(['error'], { replaceUrl: true });
}
}

}

Fetching data from REST Web Service using Angular 2 Http

Since http requests are async, this.jsonData won't be set at the time where you try to log it to console. Instead put that log into the subscribe callback:

getData(myArg: string){     
this._myService.fetchData(myArg)
.subscribe(data => {
this.jsonData = JSON.stringify(data)
console.log(this.jsonData);
},
error => alert(error),
() => console.log("Finished")
);
}

Express rest api call with angular 2 How to

The Http get takes only url and not body as parameter.It is not a post to have body.

Try:

let params: URLSearchParams = new URLSearchParams();
params.set('roomName', roomName);
return this
.http
.get(`/api/room/byName/${roomName}`)
.map((response: Response) => response.json());


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