WebClient Flux to List not working with block - spring-boot

Question

I am new to webclient. I have create a generic common library for inter microservice communication.
I am trying to post some data to get persist using webclient which works fine and able to get the data as well.
Now I need to some business logic on the return data by the web client. For that I am trying to convert the Flux to List of object, I am getting
java.lang.IllegalStateException: block()/blockFirst()/blockLast() are
* blocking, which is not supported in thread reactor-http-nio-3
Code:
#Override
public Flux<EmployeeDTO> getAllEmployees() {
WebClientRequest<EmployeeDTO> employeeWebClientRequest = new WebClientRequest<>();
employeeWebClientRequest.setRequestTracker(UUID.randomUUID().toString());
employeeWebClientRequest.setContentType("application/json");
EmployeeDTO employeeDTO = new EmployeeDTO();
employeeDTO.setEmployeeName("MTRS");
employeeDTO.setFirstname("MT");
employeeDTO.setLastName("RS");
employeeWebClientRequest.setWebClientBody(employeeDTO);
employeeWebClientRequest.setEndPoint("http://localhost:8080/api/employees");
Flux<EmployeeDTO> postListAsynchronousWebClient = webClientEmployee
.postListAsynchronousWebClient(employeeWebClientRequest, EmployeeDTO.class);
List<EmployeeDTO> block = postListAsynchronousWebClient.collectList().block();// Failing Line
/*
*
* java.lang.IllegalStateException: block()/blockFirst()/blockLast() are
* blocking, which is not supported in thread reactor-http-nio-3 at
* reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:83)
* ~[reactor-core-3.4.21.jar:3.4.21] Suppressed:
* reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
*/
return postListAsynchronousWebClient;
}
public <T> Flux<K> postListAsynchronousWebClient(WebClientRequest<T> webClientRequest, Class<K> clazz) {
if (null == webClientRequest.getRequestTracker()) {
return Flux.error(new MtampWebClientException("", requestTrackerErrorCode, requestTrackerErrorMessage));
}
ResponseSpec retrieve = performPostWebRequest(webClientRequest);
return retrieve.bodyToFlux(clazz).doOnNext(resp -> webClientResponse(webClientRequest, resp));
}
private <T> ResponseSpec performPostWebRequest(WebClientRequest<T> webClientRequest) {
WebClient client = webClientBuilder();
client.get().headers(h-> System.out.println(h));
LinkedMultiValueMap<String, String> map = setHeaders(webClientRequest);
Consumer<HttpHeaders> consumer = it -> it.addAll(map);
ResponseSpec retrieve;
if (null != webClientRequest.getPathParam()) {
retrieve = client.post().uri(webClientRequest.getEndPoint() + "/" + webClientRequest.getPathParam())
.bodyValue(webClientRequest.getWebClientBody()).headers(consumer).retrieve();
} else {
retrieve = client.post().uri(webClientRequest.getEndPoint()).bodyValue(webClientRequest.getWebClientBody())
.headers(consumer).retrieve();
}
return retrieve;
}
private WebClient webClientBuilder() {
HttpClient httpClient = HttpClient.create().option(ChannelOption.CONNECT_TIMEOUT_MILLIS, webClientTimeOut)
.responseTimeout(Duration.ofMillis(webClientResponseTimeOut)).doOnConnected(
conn -> conn.addHandlerLast(new ReadTimeoutHandler(webClientReadTimeOut, TimeUnit.MILLISECONDS))
.addHandlerLast(new WriteTimeoutHandler(webClientWriteTimeOut, TimeUnit.MILLISECONDS)));
return WebClient.builder().filter(new WebClientFilter()).filter(ExchangeFilterFunction.ofResponseProcessor(this::errorHandler))
.clientConnector(new ReactorClientHttpConnector(httpClient)).build();
}
The whole exception log below:
java.lang.IllegalStateException: block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-3
at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:83) ~[reactor-core-3.4.21.jar:3.4.21]
Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:
Error has been observed at the following site(s):
*__checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
*__checkpoint ⇢ HTTP GET "/api/employees" [ExceptionHandlingWebHandler]
Original Stack Trace:
at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:83) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Mono.block(Mono.java:1707) ~[reactor-core-3.4.21.jar:3.4.21]
at com.mt.mtamp.webclient.service.impl.WebClientServiceImpl.getAllEmployees(WebClientServiceImpl.java:71) ~[classes/:na]
at com.mt.mtamp.webclient.controller.WebClientController.getAllEmployees(WebClientController.java:50) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
at org.springframework.web.reactive.result.method.InvocableHandlerMethod.lambda$invoke$0(InvocableHandlerMethod.java:144) ~[spring-webflux-5.3.22.jar:5.3.22]
at reactor.core.publisher.FluxFlatMap.trySubscribeScalarMap(FluxFlatMap.java:152) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoFlatMap.subscribeOrReturn(MonoFlatMap.java:53) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:57) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:240) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.onComplete(MonoIgnoreThen.java:203) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onComplete(MonoFlatMap.java:181) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Operators.complete(Operators.java:137) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoZip.subscribe(MonoZip.java:120) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Mono.subscribe(Mono.java:4397) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:157) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:74) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.innerNext(FluxConcatMap.java:282) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:863) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:129) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onNext(MonoPeekTerminal.java:180) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:2398) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.request(MonoPeekTerminal.java:139) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:171) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:2194) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:2068) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:96) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onSubscribe(MonoPeekTerminal.java:152) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoJust.subscribe(MonoJust.java:55) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Mono.subscribe(Mono.java:4397) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:451) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:219) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:165) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:87) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.Mono.subscribe(Mono.java:4397) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:263) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:51) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.InternalMonoOperator.subscribe(InternalMonoOperator.java:64) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.core.publisher.MonoDeferContextual.subscribe(MonoDeferContextual.java:55) ~[reactor-core-3.4.21.jar:3.4.21]
at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:967) ~[reactor-netty-http-1.0.21.jar:1.0.21]
at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:677) ~[reactor-netty-core-1.0.21.jar:1.0.21]
at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:478) ~[reactor-netty-core-1.0.21.jar:1.0.21]
at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:570) ~[reactor-netty-http-1.0.21.jar:1.0.21]
at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:93) ~[reactor-netty-core-1.0.21.jar:1.0.21]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:222) ~[reactor-netty-http-1.0.21.jar:1.0.21]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:327) ~[netty-codec-4.1.79.Final.jar:4.1.79.Final]
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:299) ~[netty-codec-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:722) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:658) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:584) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:496) ~[netty-transport-4.1.79.Final.jar:4.1.79.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.79.Final.jar:4.1.79.Final]
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.79.Final.jar:4.1.79.Final]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.79.Final.jar:4.1.79.Final]
at java.base/java.lang.Thread.run(Thread.java:833) ~[na:na]