Simple logging dump of WebClient request? - spring

Question

I'm trying to use Spring WebClient to make some basic REST API calls. I'm getting an error that the request is malformed, but I can't tell exactly why. Is there any way to easily log the contents of the request (really, just the request body)? Everything I find online is super complicated. Here's what I have:
LinkedMultiValueMap params = new LinkedMultiValueMap();
params.add("app_id", getOneSignalAppId());
params.add("included_segments", inSegment);
params.add("content_available", true);
params.add("contents", new LinkedMultiValueMap() {{
add("en", inTitle);
}});
BodyInserters.MultipartInserter inserter = BodyInserters.fromMultipartData(params);
WebClient client = WebClient.builder()
.baseUrl("https://onesignal.com")
.defaultHeader(HttpHeaders.AUTHORIZATION, "Basic " + getOneSignalKey())
.defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
.defaultHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE)
.build();
Mono<NotificationResponse> result = client
.post()
.uri("/api/v1/notifications")
.body(inserter)
.retrieve()
.bodyToMono(NotificationResponse.class);
I just want a string of the JSON that will be inserted into the request body.

Answer 1

You can create your own wrapper/proxy class around the JSON encoder (assuming you're using JSON) and intercept the serialized body before it is sent into the intertubes.
If your request is going to send JSON.
Specifically, you would extend the encodeValue method (or encodeValues in case of streaming data) of Jackson2JsonEncoder (the default encoder). Then you can do with that data what you wish, such as logging etc. And you could even do this conditionally based on environment/profile.
This custom logging-encoder can be specified when creating the WebClient, by providing it as a codec:
CustomBodyLoggingEncoder bodyLoggingEncoder = new CustomBodyLoggingEncoder();
WebClient.builder()
.codecs(clientDefaultCodecsConfigurer -> {
clientDefaultCodecsConfigurer.defaultCodecs().jackson2JsonEncoder(bodyLoggingEncoder);
clientDefaultCodecsConfigurer.defaultCodecs().jackson2JsonDecoder(new Jackson2JsonDecoder(new ObjectMapper(), MediaType.APPLICATION_JSON));
})
...
I made a blog post about this. You might be able to find the encoder for Multipart data and apply similar principles
For completeness, the encoder might look something like this:
public class CustomBodyLoggingEncoder extends Jackson2JsonEncoder {
#Override
public DataBuffer encodeValue(final Object value, final DataBufferFactory bufferFactory,
final ResolvableType valueType, #Nullable final MimeType mimeType, #Nullable final Map<String, Object> hints) {
// Encode/Serialize data to JSON
final DataBuffer data = super.encodeValue(value, bufferFactory, valueType, mimeType, hints);
// This is your code:
SomethingAmazing.doItWithThisData(extractBytes(data));
// Return the data as normal
return data;
}
private byte[] extractBytes(final DataBuffer data) {
final byte[] bytes = new byte[data.readableByteCount()];
data.read(bytes);
// We've copied the data above to our array, but must reset the buffer for actual usage
data.readPosition(0);
return bytes;
}
}
Hope that helps somehow!