Webflux Spring 2.1.2 customize Content-Type - spring

Question

I am trying to post via WebClient to get microsoft token:
public WebClient getWebclient() {
TcpClient client = TcpClient.create()
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 10000)
.doOnConnected(connection -> connection.addHandlerLast(new ReadTimeoutHandler(15)).addHandlerLast(new WriteTimeoutHandler(15)));
ExchangeStrategies strategies = ExchangeStrategies.builder()
.codecs(configurer -> {
configurer.registerDefaults(true);
FormHttpMessageReader formHttpMessageReader = new FormHttpMessageReader();
formHttpMessageReader.setEnableLoggingRequestDetails(true);
configurer.customCodecs().reader(formHttpMessageReader);
})
.build();
return WebClient.builder()
.clientConnector(new ReactorClientHttpConnector(HttpClient.from(client).followRedirect(true)))
.exchangeStrategies(strategies)
.filter(logRequest())
.filter(logResponse())
.build();
}
MultiValueMap<String, String> credentials = new LinkedMultiValueMap<>();
credentials.add("grant_type", "password");
credentials.add("client_id", oauthClientId);
credentials.add("resource", oauthResource);
credentials.add("scope", oauthScope);
credentials.add("username", oauthUsername);
credentials.add("password", oauthPassword);
Mono<MicrosoftToken> response = webClientService.getWebclient().post()
.uri(oauthUrl)
.contentType(MediaType.APPLICATION_FORM_URLENCODED)
.body(BodyInserters.fromFormData(credentials))
.retrieve()
.onStatus(HttpStatus::is4xxClientError, clientResponse ->
Mono.error(new WebClientException(clientResponse.bodyToMono(String.class), clientResponse.statusCode())))
.bodyToMono(MicrosoftToken.class);
this.cachedToken = response.block();
The problem ist, that microsoft cannot handle a Content-type: application/x-www-form-urlencoded;charset=UTF-8.
Spring is automatically adding the charset=UTF-8 to the request. I need to get rid of this additional charset. I need a Content-Type: application/x-www-form-urlencoded. Is this possible? Otherwise i need to downgrade my spring version to 2.0.0 where the charset is not automatically be added.
My Debug Logs print:
2019-03-14 10:08:42 DEBUG [reactor.netty.channel.ChannelOperationsHandler]:
[id: 0x5d6effce, L:/192.168.148.14:52285 -
R:login.microsoftonline.de/51.4.136.42:443] Writing object
DefaultHttpRequest(decodeResult: success, version: HTTP/1.1)
POST /common/oauth2/token HTTP/1.1
user-agent: ReactorNetty/0.8.4.RELEASE
host: login.microsoftonline.de
Content-Type: application/x-www-form-urlencoded;charset=UTF-8
Content-Length: 205
2019-03-14 10:08:42 DEBUG [reactor.netty.channel.ChannelOperationsHandler]:
[id: 0x5d6effce, L:/192.168.148.14:52285 -
R:login.microsoftonline.de/51.4.136.42:443] Writing object
I tested this with spring version 2.0.0 and there the charset is not added as in the new version:
POST /common/oauth2/token HTTP/1.1
user-agent: ReactorNetty/0.7.5.RELEASE
host: login.microsoftonline.de
accept-encoding: gzip
Content-Type: application/x-www-form-urlencoded
Content-Length: 205

Answer 1

This took me the best part of a morning to find out, but I finally managed. The problem is that Webflux BodyInserters.fromFormData always sets the content type to application/x-www-form-urlencoded;charset=... regardless of what you set in the headers.
To solve this, first define this method:
/**
* This method is unfortunately necessary because of Spring Webflux's propensity to add {#code ";charset=..."}
* to the {#code Content-Type} header, which the Generic Chinese Device doesn't handle properly.
*
* #return a {#link FormInserter} that doesn't add the character set to the content type header
*/
private FormInserter<String> formInserter() {
return new FormInserter<String>() {
private final MultiValueMap<String, String> data = new LinkedMultiValueMap<>();
#Override public FormInserter<String> with(final String key, final String value) {
data.add(key, value);
return this;
}
#Override public FormInserter<String> with(final MultiValueMap<String, String> values) {
data.addAll(values);
return this;
}
#Override public Mono<Void> insert(final ClientHttpRequest outputMessage, final Context context) {
final ResolvableType formDataType =
ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class);
return new FormHttpMessageWriter() {
#Override protected MediaType getMediaType(final MediaType mediaType) {
if (MediaType.APPLICATION_FORM_URLENCODED.equals(mediaType)) {
return mediaType;
} else {
return super.getMediaType(mediaType);
}
}
}.write(Mono.just(this.data), formDataType,
MediaType.APPLICATION_FORM_URLENCODED,
outputMessage,
context.hints());
}
};
}
Then, to call your web service, do the following:
final SomeResponseObject response = WebClient
.builder()
.build()
.post()
.uri(someOrOtherUri)
.body(formInserter().with("param1", "value1")
.with("param2", "value2")
)
.retrieve()
.bodyToFlux(SomeReponseObject.class)
.blockLast();
Please note that the block above is mainly for demonstration purposes. You may or may not want to block and wait for the response.

Answer 2

Here's two ways to do it:
webClient
.mutate()
.defaultHeaders(headers -> {
headers.add("Content-Type", ContentType.APPLICATION_FORM_URLENCODED.getMimeType()
}).build()
. uri(uri)
...
OR
webClient
.post()
.uri(uri)
.body(body)
.headers(headers -> getHttpHeaders())
...
private HttpHeaders getHttpHeaders(){
HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", "application/x-www-form-urlencoded")
return headers;
}
Just a few ways you could utilize the headers consumer in .headers or .defaultHeaders..
But I don't think the charset is the issue to be honest. If you are getting application/json in your response it is probably because Microsoft is forwarding the request with that header through the redirect url you specified in your app registration.
The good news is this is probably desirable, since Microsoft returns the token fields as json, which allows you to call .bodyToMono(MicrosoftToken). I recall having issues with BodyInserters.fromFormData as it did not actually encode the values in the MultiValueMap.
This is what I'm using instead:
private BodyInserter<String, ReactiveHttpOutputMessage> getBodyInserter(Map<String,String> parameters) {
credentials.add("grant_type", encode("password"));
credentials.add("client_id", encode(oauthClientId));
credentials.add("resource", encode(oauthResource));
// and so on..
// note that parameters is a regular Map - not a MultiValueMap
BodyInserter<String, ReactiveHttpOutputMessage> bodyInserter = BodyInserters.fromObject(
parameters.entrySet().stream()
.map(entry -> entry.getKey().concat("=").concat(entry.getValue()))
.collect(Collectors.joining("&", "", "")));
return bodyInserter;
}
private String encode(String str) {
try {
return URLEncoder.encode(str, StandardCharsets.UTF_8.name());
} catch (UnsupportedEncodingException e) {
log.error("Error encoding req body", e);
}
}