Spring WebClient not processing JSON content - json

Question

I have an app that uses WebClient to fetch JSON data from ComicVine as follows:
WebClient client = WebClient.builder()
.baseUrl(url)
.defaultHeaders(
headers -> {
headers.add(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE);
headers.add(HttpHeaders.USER_AGENT, "ComiXed/0.7");
})
.build();
Mono<ComicVineIssuesQueryResponse> request =
client
.get()
.uri(url)
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.bodyToMono(ComicVineIssuesQueryResponse.class);
ComicVineIssuesQueryResponse response = request.block();
For a time this worked. But then, all of a sudden, it's throwing the following root exception when it executes:
Caused by: org.springframework.web.reactive.function.UnsupportedMediaTypeException: Content type 'application/json' not supported for bodyType=org.comixed.scrapers.comicvine.model.ComicVineIssuesQueryResponse
at org.springframework.web.reactive.function.BodyExtractors.lambda$readWithMessageReaders$12(BodyExtractors.java:201)
I'm not sure why it all of a sudden won't process JSON data. My unit test, which is explicitly returning JSON data and setting the content type properly:
private MockWebServer comicVineServer;
this.comicVineServer.enqueue(
new MockResponse()
.setBody(TEST_GOOD_BODY)
.addHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE));
Any ideas why this is the case? It's happening across multiple classes that use this same setup for WebClient and for testing.

Answer 1

After doing some digging, I added the following code to get the JSON as a String and then use ObjectMapper to convert it to the target type:
Mono<String> request =
client
.get()
.uri(url)
.accept(MediaType.APPLICATION_JSON)
.retrieve()
.bodyToMono(String.class);
String value = request.block();
ObjectMapper mapper = new ObjectMapper();
ComicVineIssuesQueryResponse response = mapper.readValue(value, ComicVineIssuesQueryResponse.class);
This quickly exposed the underlying problem, which was that two instance variables in the response were annotated with the same JSON field name. Once I fixed that, things started working correctly again.

Answer 2

you can parse the json content to string without calling block method.
option 1) Jackson2Tokenizer
option 2) put your code which is calling "objectMapper.readValue(..) .." inside map operator.