Handling CORS when calling 3rd party API

问题

yes this is a very famous question , I have tried many ways mentioned in the previous stack-overflow QnA, but nothing worked. I am trying to use BANZAI-Cloud API in my application , but it gives the following error

here is my code of the service class

import { Injectable } from '@angular/core';
import {HttpClient} from '@angular/common/http';
import { Observable } from 'rxjs';
import { HttpHeaders } from '@angular/common/http';

@Injectable({providedIn:"root"})
export class PriceTableService{

    private priceurl = "https://banzaicloud.com/cloudinfo/api/v1/providers/google/services/compute/regions/asia-east2/products"
    // private priceurl = "https://jsonplaceholder.typicode.com/posts"

    constructor(private http:HttpClient){}
    httpOptions = {
        headers: new HttpHeaders({
            'Access-Control-Allow-Methods':'DELETE, POST, GET, OPTIONS',
            'Access-Control-Allow-Headers':'Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With',
            'Content-Type':  'application/json',
            'Access-Control-Allow-Origin':'http://localhost:4200'
        })
      };
    getPrices(){
            this.http.get(this.priceurl,this.httpOptions).subscribe(result=>{
            console.log(result);
            return(result);
        })
     }
    ngOnInit() {
    }
}

this API works in the POSTMAN and CHROME but cannot get data into my angular application , when I replace the URL with any other fake API I can get data ,but the above mentioned API is not giving data ,If anyone can help me to clear this problem it would be a great help.

回答1:

First, you need to understand that the CORS check is done by the browser. It's a W3C specification. Any extensions or tools like Postman are not bound with that. That's the reason you got the result through Postman.

And the other thing is, you have tried to add Access-Control-Allow-Origin header to the request. That's not what CORS specification expects. You need to have the Access-Control-Allow-Origin header in the response. That means it needs to be added by the server-side.

Since you are calling a 3rd party API, I believe you don't have control over the server. Therefore asking to handle the CORS issue by setting up Access-Control-Allow-Origin will not be possible.

There are 3 ways you can resolve this problem assuming you don't have access to the server.

By disabling CORS check in the browser(Not Recommended for Production).
By using a CORS plugin in the browser(Not Recommended for Production).
By requesting the resource through a proxy - The simplest way, what you can do is, write a small node server (or if you already have a back-end associate it with your front-end you can use it) which does the request for the 3rd party API and sends back the response. And in that server response now you can allow cross-origin header.

回答2:

As per this answer's 3rd way I have made a small node server with express and called BANZAICLOUD using the following code.

const express=require('express');
const request = require('request');
const app=express();

app.get('/data',(req,res,next)=>{
    request('https://banzaicloud.com/cloudinfo/api/v1/providers/google/services/compute/regions/asia-east2/products',
     function (error, response, body) {
         res.send(body)
    });  
});
const port =process.env.port || 3000;
app.listen(port,()=>{
    console.log(`From port ${port}`);
});

Then you can use the http://localhost:3000/data in the front end and get data.

回答3:

Check your headers. You might be sending headers that the external API doesnt like (like Authorization etc.) which might lead to this error.

来源：https://stackoverflow.com/questions/58122615/handling-cors-when-calling-3rd-party-api

标签

cors

angular-httpclient