Let’s give this a try…
//FileName: login.service.ts
import { Injectable } from '@angular/core';
import { HttpParams, HttpClient, HttpHeaders } from '@angular/common/http';
import { HttpErrorResponse, HttpResponse } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError, retry } from 'rxjs/operators';
@Injectable()
export class LoginService {
private _loginUrl="http://1.2.3.4/signin"; //the api url where we need to make a call
constructor(private _http: HttpClient) {} //this initialized the HttpClient which we use to do a post or get call
//setting body of the parameters to send via post
private body = new HttpParams()
.set('username', 'onetap')
.set('password', '123456');
checkLogin(){
return this._http.post(this._loginUrl,
this.body.toString(),
{
headers: new HttpHeaders()
.set('Content-Type', 'application/x-www-form-urlencoded')
}
)
.pipe(
catchError(this.handleError) // then handle the error
);
}
private handleError(error: HttpErrorResponse) {
if (error.error instanceof ErrorEvent) {
// A client-side or network error occurred. Handle it accordingly.
console.error('An error occurred:', error.error.message);
} else {
// The backend returned an unsuccessful response code.
// The response body may contain clues as to what went wrong,
console.error(
`Backend returned code ${error.status}, ` +
`body was: ${error.error}`);
}
// return an observable with a user-facing error message
return throwError(
'Something bad happened; please try again later.');
}
}Let me explain this now…
First things first… go and refer this link , which is the basic guide with live example on how setup httpclient and use it.
In this code lets start with imports:
Injectable: A decorator which will help you inject this service into any component you need. Just import then set it in @Component providers then create instance of it in constructor and use it using this.
HttpParams: Set the parameter or data to send for ‘Content-Type’: ‘application/x-www-form-urlencoded’.
HttpClient: This is the module using which we implement the get, post put methods.
throwError, catchError, retry: This could be your homework to research on.
checkLogin() implements the post method. Using HttpParams we create the body instance and pass it to checkLogin.
Post request will take 3 parametes. 1. Url, 2. Data or body to send, 3. Optional headers.
Now we call this checkLogin from our components onSubmit method given below
onSubmit() {
this.loginService.checkLogin()
.subscribe(resp => {
this.user = {
username: resp['username'],
email: resp['email'],
password: resp['password']
};
console.log(this.user);//Check if we are getting data from server
});
}After all this is done. If you are getting a CORS issue which you might get if you are on local host or a different server. Use the code below
This is at the server end code
do
npm install cors --save
and just add these lines in your main file where your request is going.
const cors = require('cors');
const express = require('express');
let app = express();
app.use(cors());
app.options('*', cors());