Spring webClient generate NullPointException after going through the filter - spring

Question

I want to do exception handling. When StatusCode 200, but not the desired body.
To make the processing global I am using filter.
below is the code.
public WebClient webClient() {
return WebClient.builder()
.filter(ExchangeFilterFunction.ofResponseProcessor(response -> {
// statusCode 400 || 500
if (response.statusCode().isError()) {
return response.bodyToMono(String.class)
.flatMap(body ->
Mono.error(new ExternalClientException(body))
)
);
}
// statusCode 200
return response.bodyToMono(String.class)
.flatMap(body -> {
if (YanoljaConstants.EMPTY_BODY.contains(body)) {
return Mono.error(new ExternalClientException(body))
.cast(ClientResponse.class);
}
return Mono.just(response); // normal
});
}))
.build();
}
And the actual client code is shown below.
public Foo getPlace(int no) {
return Objects.requireNonNull(contentsApiV2Client.get()
.uri(uriBuilder -> uriBuilder.path("/path").build(no))
.retrieve()
.bodyToMono(new ParameterizedTypeReference<Foo>() {
})
.block());
}
When using this, NullPointerException occurs when responding normally after going through the filter(return Mono#just(response)).
I want clear this issue.
For reference, the below code works normally.
public WebClient webClient() {
return WebClient.builder()
.filter(ExchangeFilterFunction.ofResponseProcessor(response -> {
// statusCode 400 || 500
if (response.statusCode().isError()) {
return response.bodyToMono(String.class)
.flatMap(body ->
Mono.error(new ExternalClientException(body))
)
);
}
return Mono.just(response); // normal
}))
.build();
}
Thank you. waiting for your answer!
Solve!
public WebClient webClient() {
return WebClient.builder()
.filter(ExchangeFilterFunction.ofResponseProcessor(response -> {
// statusCode 400 || 500
if (response.statusCode().isError()) {
return response.bodyToMono(String.class)
.flatMap(body ->
Mono.error(new ExternalClientException(body))
)
);
}
// statusCode 200
return response.bodyToMono(String.class)
.flatMap(body -> {
if (YanoljaConstants.EMPTY_BODY.contains(body)) {
return Mono.error(new ExternalClientException(body))
.cast(ClientResponse.class);
}
return Mono.just(ClientResponse.create(HttpStatus.OK)
.header(HttpHeaders.CONTENT_TYPE, "application/json")
.body(body)
.build()); // normal
});
}))
.build();
}
I realized that running the monoTobody method consumes it and the value disappears. So I solved it by creating a new ClientResponse.
Thank you.