Unable to change content type using modifyResponseBody filter

[ghost]

I'm trying to create a route to a service that returns an XML response. I need to get some data from the response, and then use it to create a custom object which will be returned as JSON from the gateway. I'm trying to use the modifyResponseBody filter to do this, but it seems to be having an issue changing the content type. The filter takes "newContentType" as an argument, so I would except it to be able to change the content type of the response, similarly to how the content type can be changed with the modifyRequestBody filter which does seem to work properly.

I'm using spring cloud gateway version 2.2.5.RELEASE

Below is a code sample for the route which is using the filter, and below that is the stack trace of the error I'm seeing

@Bean
public RouteLocator billingServiceRoute(RouteLocatorBuilder builder) {
	return builder.routes()
		.route(r -> r.path("/billing-service")
			.filters(f ->
				f.modifyResponseBody(String.class, ServiceResponse.class, MediaType.APPLICATION_JSON_VALUE,
					((exchange, response) -> Mono.just(new ServiceResponse(response, System.currentTimeMillis())))))
			.uri("http://localhost:8080/billing-service")
	).build();
}

2020-10-09 09:45:15.180 ERROR 94422 --- [ctor-http-nio-4] a.w.r.e.AbstractErrorWebExceptionHandler : [8add6a40-1]  500 Server Error for HTTP POST "/billing-service"

org.springframework.web.reactive.function.UnsupportedMediaTypeException: Content type 'application/xml;charset=UTF-8' not supported for bodyType=com.example.gatewayexample.ServiceResponse
	at org.springframework.web.reactive.function.BodyInserters.unsupportedError(BodyInserters.java:391) ~[spring-webflux-5.2.9.RELEASE.jar:5.2.9.RELEASE]
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
	|_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
	|_ checkpoint ⇢ HTTP POST "/billing-service" [ExceptionHandlingWebHandler]
Stack trace:
		at org.springframework.web.reactive.function.BodyInserters.unsupportedError(BodyInserters.java:391) ~[spring-webflux-5.2.9.RELEASE.jar:5.2.9.RELEASE]
		at org.springframework.web.reactive.function.BodyInserters.lambda$writeWithMessageWriters$11(BodyInserters.java:381) ~[spring-webflux-5.2.9.RELEASE.jar:5.2.9.RELEASE]
		at java.base/java.util.Optional.orElseGet(Optional.java:369) ~[na:na]
		at org.springframework.web.reactive.function.BodyInserters.writeWithMessageWriters(BodyInserters.java:381) ~[spring-webflux-5.2.9.RELEASE.jar:5.2.9.RELEASE]
		at org.springframework.web.reactive.function.BodyInserters.lambda$fromPublisher$4(BodyInserters.java:185) ~[spring-webflux-5.2.9.RELEASE.jar:5.2.9.RELEASE]
		at org.springframework.cloud.gateway.filter.factory.rewrite.ModifyResponseBodyGatewayFilterFactory$ModifiedServerHttpResponse.writeWith(ModifyResponseBodyGatewayFilterFactory.java:276) ~[spring-cloud-gateway-core-2.2.5.RELEASE.jar:2.2.5.RELEASE]
		at org.springframework.cloud.gateway.filter.NettyWriteResponseFilter.lambda$filter$2(NettyWriteResponseFilter.java:100) ~[spring-cloud-gateway-core-2.2.5.RELEASE.jar:2.2.5.RELEASE]
		at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:44) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:153) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.ignoreDone(MonoIgnoreThen.java:190) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreInner.onComplete(MonoIgnoreThen.java:240) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onComplete(MonoPeekTerminal.java:292) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.Operators$MonoSubscriber.onComplete(Operators.java:1824) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenAcceptInner.onComplete(MonoIgnoreThen.java:314) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.Operators.complete(Operators.java:135) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoEmpty.subscribe(MonoEmpty.java:45) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:153) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.ignoreDone(MonoIgnoreThen.java:190) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreInner.onComplete(MonoIgnoreThen.java:240) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2346) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onSubscribeInner(MonoFlatMapMany.java:143) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onNext(MonoFlatMapMany.java:182) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.SerializedSubscriber.onNext(SerializedSubscriber.java:99) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.FluxRetryWhen$RetryWhenMainSubscriber.onNext(FluxRetryWhen.java:162) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.core.publisher.MonoCreate$DefaultMonoSink.success(MonoCreate.java:156) ~[reactor-core-3.3.10.RELEASE.jar:3.3.10.RELEASE]
		at reactor.netty.http.client.HttpClientConnect$HttpIOHandlerObserver.onStateChange(HttpClientConnect.java:436) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:518) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at reactor.netty.resources.PooledConnectionProvider$DisposableAcquire.onStateChange(PooledConnectionProvider.java:561) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at reactor.netty.resources.PooledConnectionProvider$PooledConnection.onStateChange(PooledConnectionProvider.java:448) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:604) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:96) ~[reactor-netty-0.9.12.RELEASE.jar:0.9.12.RELEASE]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324) ~[netty-codec-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:311) ~[netty-codec-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:425) ~[netty-codec-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276) ~[netty-codec-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493) ~[netty-transport-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) ~[netty-common-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.52.Final.jar:4.1.52.Final]
		at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.52.Final.jar:4.1.52.Final]
		at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

[spencergibb]

It's an issue with serialization. Spring doesn't know how to turn om.example.gatewayexample.ServiceResponse into json. Do you have Jackson on your classpath?

[spring-cloud-issues]

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[spring-cloud-issues]

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