Oauth2 in a Proxy - oauth-2.0

Question

I need to build a kind of Java Proxy+ that handle the OAuth2 flow. The idea is to login in this "Proxy+" and do the OAuth2 flow until the Proxy+ has received the token + refresh token.
After that you login onto the Proxy+ with Username and Password or something else that give you a session. The proxy will handle generically all your web requests and add the Oauth2 token to each request. If necessary the also refresh the token.
How would you implement the Proxy Part where requests are taken and enhanced and maybe a token refresh is requested. This question is NOT about the OAuth2 flow and NOT about how to get the token in the first place.
I think i try a servlet filter that intercepts all requests and enhance the request. This way it is also generic to all urls called. Any better ideas?

Answer 1

Found a better way, this is the Spring way of a generic Proxy :-)
#RequestMapping("/**")
public ResponseEntity<byte[]> genericRequest(RequestEntity<?> inboundRequestEntity, HttpServletRequest request) {
URI outboundUri = UriComponentsBuilder.fromHttpUrl(this.targetBaseUrl)
.path(removeUrlPart(request))
.query(request.getQueryString())
.build(true)
.toUri();
HttpHeaders headers = filterHeaders(inboundRequestEntity.getHeaders());
BodyBuilder builder = RequestEntity
.method(requireNonNull(inboundRequestEntity.getMethod()), outboundUri)
.headers(headers);
RequestEntity<?> outboundRequestEntity = inboundRequestEntity.hasBody() ? builder.body(requireNonNull(inboundRequestEntity.getBody())) : builder.build();
try {
LOGGER.info("Will call url '{}' with method '{}'", outboundRequestEntity.getUrl(), outboundRequestEntity.getMethod());
ResponseEntity<byte[]> responseEntity = this.restTemplate.exchange(outboundRequestEntity);
return ResponseEntity.status(responseEntity.getStatusCode())
.headers(filterHeaders(responseEntity.getHeaders()))
.body(responseEntity.getBody());
} catch (
HttpStatusCodeException e) {
return ResponseEntity.status(e.getRawStatusCode())
.headers(filterHeaders(e.getResponseHeaders()))
.body(e.getResponseBodyAsByteArray());
}
}
private static HttpHeaders filterHeaders(HttpHeaders originalHeaders) {
HttpHeaders filteredResponseHeaders = new HttpHeaders();
filteredResponseHeaders.putAll(originalHeaders);
filteredResponseHeaders.remove(CONTENT_LENGTH);
filteredResponseHeaders.remove(DATE);
return filteredResponseHeaders;
}