Angular2 : detect error from HTTP post - http

Question

I cannot interecept error from http post
a part of my mservice (http post method)
addApplicationLink(applicationLink: ApplicationLink){
let body = JSON.stringify(applicationLink);
let requestHeaders = new Headers();
var headers = new Headers();
headers.set('Content-Type', ['application/json; charset=utf-8']);
let reqoptions = new RequestOptions({
headers: headers
});
return this._http.post(this._applicationLinksUrl + this._linkServicePath,body,{headers: headers});
in my component :
addApplicationLink() {
//todo
this.addNewLink = false;
/* check if must be done after call real rest service */
//this.applicationLinks.push(this.applicationLinkAdd);
this._applicationLinkService.addApplicationLink(this.applicationLinkAdd)
.subscribe(data => {
this.applicationLinks.push(this.applicationLinkAdd)
},
error => {
// handle error
console.error('this an erreor ' + error.status)
}
)
When user tries to add two same applicationlinks , the backend returns an error 409
But when I execute , error.status displays 200 in browser console
I see also in browser console
XMLHttpRequest cannot load http://localhost:7001...... No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. The response had HTTP status code 409.
rem : Http post is made with json , thus there is a prefligth call
Have you an idea to intercept error 409 ?

Answer 1

In fact, your server doesn't send back the CORS header (Access-Control-Allow-Origin' header is missing). This prevent the browser from providing the actual 409 error to the Angular2 application within the browser.
You need to fix first the problem on the server and you will be able to see this 409 error.
For more details about how CORS works, you could have a look at this article:
http://restlet.com/blog/2015/12/15/understanding-and-using-cors/