Spring REST Controller is not responding to Angular request

Question

I have an app to create server certificate requests, just as if one were using java keytool or something. I'm trying to return the created certificate request and the key in a zip file, but for the life of me, I can't get my REST controller to respond to the http request. CORRECTION: The controller responds, but the code within the method is never executed.

The server does receive the request, because my CORS filter is executed. But I have a debug set in the controller method, and it's never triggered. Is the signature of the method correct? I need another set of eyes, please?

Here is my controller code:

@RequestMapping(method = RequestMethod.POST, value = "/generateCert/")
public ResponseEntity<InputStreamResource> generateCert(@RequestBody CertInfo certInfo) {
    System.out.println("Received request to generate CSR...");

    byte[] responseBytes = commonDataService.generateCsr(certInfo);
    InputStreamResource resource = new InputStreamResource(new ByteArrayInputStream(responseBytes));

    System.out.println("Generated CSR with length of " + responseBytes.length);
    return ResponseEntity.ok()
            .header(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=certificate.zip")
            .contentType(MediaType.parseMediaType("application/zip"))
            .contentLength(responseBytes.length)
            .body(resource);
}

And here is the Angular request:

generateCertificate(reqBody: GenerateCert) {
   let headers = new Headers();
   headers.append('Content-Type', 'application/json');

   this.http.post(this.urlGenerateCert, JSON.stringify(reqBody), {headers: headers}).subscribe(
    (data) => {
        let dataType = data.type;
        let binaryData = [];
        binaryData.push(data);
        this.certBlob = new Blob(binaryData);
    });
    return this.certBlob;
 }

And finally, the request and response headers I copied from the Network Panel:

Response
Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: Content-Type, Authorization, Accept, X-Requested-With, remember-me
Access-Control-Allow-Methods: POST, GET, OPTIONS
Access-Control-Allow-Origin: *
Access-Control-Max-Age: 3600
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Content-Length: 0
Date: Thu, 27 Dec 2018 22:48:00 GMT
Expires: 0
Location: http://localhost:8102/login
Pragma: no-cache
Set-Cookie: JSESSIONID=EDACE17328628D579670AD0FB53A6F35; Path=/; HttpOnly
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 1; mode=block

Request
Accept: application/json, text/plain, */*
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9
Connection: keep-alive
Content-Length: 205
Content-Type: application/json
Host: localhost:8102
Origin: http://localhost:4200
Referer: http://localhost:4200/generateCerts
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36

I really struggled with getting CORS working, so maybe that's interfering with the request? I hate to post all that code unless absolutely necessary. Anybody got any ideas?

Here we go again. http.post returns an Observable<Blob>. Not a Blob. Why? Because AJAX is asynchronous. So it returns an observable, that allows you to be notifid, much later, when the response is finally available. When you execute this.certBlob, you do it immediately after you've sent the request. The response has not come back yet. So this.certBlob is undefined. A service must return an observable. The component interested in the response must subscribe to the returned observable, to be notified when the certificate has come back. — JB Nizet
– JB Nizet, Commented Dec 27, 2018 at 23:07
You do subscribe. The, right after you've subscribed, and thus sent the request, you return this.certBlob, which is undefied, since it will only be populated much later, after the method has returned for a long time, when the callback passed to subscribe has been called because the response has finally comes back from the server. You can't eat a toast immediately after you've put it in the toaster. You need to wait until the toaster tells you that the toast s grilled. — JB Nizet
– JB Nizet, Commented Dec 27, 2018 at 23:15
I told you already. Read my first comment. The service must return an abservable. I.e. return this.http.post(...); The component which calls te service and wants to access the certificate must subscribe to the observable returned by the service. Do NOT subscribe in the service. — JB Nizet
– JB Nizet, Commented Dec 27, 2018 at 23:18
Why not use a REST Client e.g. Postman to test the endpoint first. This will help to know exactly if the problem is with the angular app or the spring-boot app. — Olantobi
– Olantobi, Commented Jan 2, 2019 at 20:50

Nikhil · Accepted Answer · 2019-01-04 17:12:34Z

1

When Angular encounters this statement

this.http.post(url,body).subscribe(data => # some code
);

It comes back immediately to run rest of the code while service continues to execute. Just like Future in Java.

Here if you

return this.cert;

You will not get the value that may eventually get populated by the this.http service. Since the page has already rendered and the code executed. You can verify this by including this within and outside the Observable.

console.log(“Inside/outside observable” + new Date().toLocalTimeString());

answered Jan 4, 2019 at 17:12

Nikhil

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Oleg Kurbatov · Accepted Answer · 2019-01-06 19:20:14Z

1

Listing of request/response headers lack information on URL, method and most important response status code.

Seeing Location: http://localhost:8102/login among response headers I can guess that it could be 401 Unauthorized or anything else that redirects to the login page. Hence, if there is an auth filter in the filter chain, it may be a culprit.

The following request headers

Host: localhost:8102
Origin: http://localhost:4200

suggests that you are doing CORS and the CORS filter may be involved indeed and fulfill response before the request gets routed to the controller. I suggest setting a breakpoint into the CORS filter (and into others if any) and debug it to the point where the response is returned.

answered Jan 6, 2019 at 19:20

Oleg Kurbatov

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1 Comment

aatuc210 Over a year ago

Yes, that's exactly what I did, and I discovered the request was making it to the server, but not my controller method.

this_is_om_vm · Accepted Answer · 2019-01-04 10:43:43Z

0

define a proxy.conf.json

{
"/login*": {
    "target":"http://localhost:8080",
    "secure":false,
    "logLevel":"debug"
    }
}

now in your package.json

"scripts": {
    "start":"ng serve --proxy-config proxy.config.json"
}

I think there is issue while getting connection in both webapp.please try .

answered Jan 4, 2019 at 10:43

this_is_om_vm

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aatuc210 · Accepted Answer · 2019-01-08 21:56:24Z

0

Thanks to everyone who contributed. I discovered the error was due to the headers of my controller method. After changing them, the method was invoked properly. This is what worked:

@RequestMapping(method = RequestMethod.POST, path = "/generateCert", 
    produces = {MediaType.APPLICATION_OCTET_STREAM_VALUE}, consumes = {MediaType.APPLICATION_JSON_VALUE})
public ResponseEntity<byte[]> generateCert(@RequestBody CertInfo certInfo) {
    byte[] responseBytes = commonDataService.generateCsr(certInfo);    
    return ResponseEntity.ok()
            .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_OCTET_STREAM_VALUE)
            .contentLength(responseBytes.length)
            .body(responseBytes);
}

answered Jan 8, 2019 at 21:56

aatuc210

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