Expose status handler at WebClient.Builder level

See gh-28533

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java

@@ -21,6 +21,7 @@ import java.nio.charset.Charset;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -29,6 +30,7 @@ import java.util.function.Function;
 import java.util.function.IntPredicate;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
@@ -84,21 +86,35 @@ class DefaultWebClient implements WebClient {
 	@Nullable
 	private final Consumer<RequestHeadersSpec<?>> defaultRequest;
 
+	private final List<DefaultResponseSpec.StatusHandler> defaultStatusHandlers;
+
 	private final DefaultWebClientBuilder builder;
 
 
 	DefaultWebClient(ExchangeFunction exchangeFunction, UriBuilderFactory uriBuilderFactory,
 			@Nullable HttpHeaders defaultHeaders, @Nullable MultiValueMap<String, String> defaultCookies,
-			@Nullable Consumer<RequestHeadersSpec<?>> defaultRequest, DefaultWebClientBuilder builder) {
+			@Nullable Consumer<RequestHeadersSpec<?>> defaultRequest,
+			@Nullable Map<Predicate<HttpStatusCode>, Function<ClientResponse, Mono<? extends Throwable>>> statusHandlerMap,
+			DefaultWebClientBuilder builder) {
 
 		this.exchangeFunction = exchangeFunction;
 		this.uriBuilderFactory = uriBuilderFactory;
 		this.defaultHeaders = defaultHeaders;
 		this.defaultCookies = defaultCookies;
 		this.defaultRequest = defaultRequest;
+		this.defaultStatusHandlers = initStatusHandlers(statusHandlerMap);
 		this.builder = builder;
 	}
 
+	private static List<DefaultResponseSpec.StatusHandler> initStatusHandlers(
+			@Nullable Map<Predicate<HttpStatusCode>, Function<ClientResponse, Mono<? extends Throwable>>> handlerMap) {
+
+		return (CollectionUtils.isEmpty(handlerMap) ? Collections.emptyList() :
+				handlerMap.entrySet().stream()
+						.map(entry -> new DefaultResponseSpec.StatusHandler(entry.getKey(), entry.getValue()))
+						.collect(Collectors.toList()));
+	};
+
 
 	@Override
 	public RequestHeadersUriSpec<?> get() {
@@ -365,7 +381,8 @@ class DefaultWebClient implements WebClient {
 
 		@Override
 		public ResponseSpec retrieve() {
-			return new DefaultResponseSpec(exchange(), this::createRequest);
+			return new DefaultResponseSpec(
+					exchange(), this::createRequest, DefaultWebClient.this.defaultStatusHandlers);
 		}
 
 		private HttpRequest createRequest() {
@@ -502,11 +519,18 @@ class DefaultWebClient implements WebClient {
 
 		private final List<StatusHandler> statusHandlers = new ArrayList<>(1);
 
+		private final int defaultStatusHandlerCount;
+
+
+		DefaultResponseSpec(
+				Mono<ClientResponse> responseMono, Supplier<HttpRequest> requestSupplier,
+				List<StatusHandler> defaultStatusHandlers) {
 
-		DefaultResponseSpec(Mono<ClientResponse> responseMono, Supplier<HttpRequest> requestSupplier) {
 			this.responseMono = responseMono;
 			this.requestSupplier = requestSupplier;
+			this.statusHandlers.addAll(defaultStatusHandlers);
 			this.statusHandlers.add(DEFAULT_STATUS_HANDLER);
+			this.defaultStatusHandlerCount = this.statusHandlers.size();
 		}
 
 
@@ -516,10 +540,9 @@ class DefaultWebClient implements WebClient {
 
 			Assert.notNull(statusCodePredicate, "StatusCodePredicate must not be null");
 			Assert.notNull(exceptionFunction, "Function must not be null");
-			int index = this.statusHandlers.size() - 1;  // Default handler always last
+			int index = this.statusHandlers.size() - this.defaultStatusHandlerCount;  // Default handlers always last
 			this.statusHandlers.add(index, new StatusHandler(statusCodePredicate, exceptionFunction));
 			return this;
-
 		}
 
 		@Override

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,8 +22,13 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Predicate;
+
+import reactor.core.publisher.Mono;
 
 import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatusCode;
 import org.springframework.http.client.reactive.ClientHttpConnector;
 import org.springframework.http.client.reactive.HttpComponentsClientHttpConnector;
 import org.springframework.http.client.reactive.JdkClientHttpConnector;
@@ -82,6 +87,9 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 	@Nullable
 	private Consumer<WebClient.RequestHeadersSpec<?>> defaultRequest;
 
+	@Nullable
+	private Map<Predicate<HttpStatusCode>, Function<ClientResponse, Mono<? extends Throwable>>> statusHandlers;
+
 	@Nullable
 	private List<ExchangeFilterFunction> filters;
 
@@ -120,6 +128,7 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 		this.defaultCookies = (other.defaultCookies != null ?
 				new LinkedMultiValueMap<>(other.defaultCookies) : null);
 		this.defaultRequest = other.defaultRequest;
+		this.statusHandlers = (other.statusHandlers != null ? new LinkedHashMap<>(other.statusHandlers) : null);
 		this.filters = (other.filters != null ? new ArrayList<>(other.filters) : null);
 
 		this.connector = other.connector;
@@ -193,6 +202,15 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 		return this;
 	}
 
+	@Override
+	public WebClient.Builder defaultStatusHandler(Predicate<HttpStatusCode> statusPredicate,
+			Function<ClientResponse, Mono<? extends Throwable>> exceptionFunction) {
+
+		this.statusHandlers = (this.statusHandlers != null ? this.statusHandlers : new LinkedHashMap<>());
+		this.statusHandlers.put(statusPredicate, exceptionFunction);
+		return this;
+	}
+
 	@Override
 	public WebClient.Builder filter(ExchangeFilterFunction filter) {
 		Assert.notNull(filter, "ExchangeFilterFunction must not be null");
@@ -282,7 +300,9 @@ final class DefaultWebClientBuilder implements WebClient.Builder {
 		return new DefaultWebClient(filteredExchange, initUriBuilderFactory(),
 				defaultHeaders,
 				defaultCookies,
-				this.defaultRequest, new DefaultWebClientBuilder(this));
+				this.defaultRequest,
+				this.statusHandlers,
+				new DefaultWebClientBuilder(this));
 	}
 
 	private ClientHttpConnector initConnector() {

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -255,6 +255,20 @@ public interface WebClient {
 		 */
 		Builder defaultRequest(Consumer<RequestHeadersSpec<?>> defaultRequest);
 
+		/**
+		 * Register a default
+		 * {@link ResponseSpec#onStatus(Predicate, Function) status handler} to
+		 * apply to every response. Such default handlers are applied in the
+		 * order in which they are registered, and after any others that are
+		 * registered for a specific response.
+		 * @param statusPredicate to match responses with
+		 * @param exceptionFunction to map the response to an error signal
+		 * @return this builder
+		 * @since 6.0
+		 */
+		Builder defaultStatusHandler(Predicate<HttpStatusCode> statusPredicate,
+				Function<ClientResponse, Mono<? extends Throwable>> exceptionFunction);
+
 		/**
 		 * Add the given filter to the end of the filter chain.
 		 * @param filter the filter to be added to the chain

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/DefaultWebClientTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -423,6 +423,40 @@ public class DefaultWebClientTests {
 		StepVerifier.create(result).expectErrorMessage("1").verify();
 	}
 
+	@Test
+	public void onStatusHandlerRegisteredGlobally() {
+
+		ClientResponse response = ClientResponse.create(HttpStatus.BAD_REQUEST).build();
+		given(exchangeFunction.exchange(any())).willReturn(Mono.just(response));
+
+		Mono<Void> result = this.builder
+				.defaultStatusHandler(HttpStatusCode::is4xxClientError, resp -> Mono.error(new IllegalStateException("1")))
+				.defaultStatusHandler(HttpStatusCode::is4xxClientError, resp -> Mono.error(new IllegalStateException("2")))
+				.build().get()
+				.uri("/path")
+				.retrieve()
+				.bodyToMono(Void.class);
+
+		StepVerifier.create(result).expectErrorMessage("1").verify();
+	}
+
+	@Test
+	public void onStatusHandlerRegisteredGloballyHaveLowerPrecedence() {
+
+		ClientResponse response = ClientResponse.create(HttpStatus.BAD_REQUEST).build();
+		given(exchangeFunction.exchange(any())).willReturn(Mono.just(response));
+
+		Mono<Void> result = this.builder
+				.defaultStatusHandler(HttpStatusCode::is4xxClientError, resp -> Mono.error(new IllegalStateException("1")))
+				.build().get()
+				.uri("/path")
+				.retrieve()
+				.onStatus(HttpStatusCode::is4xxClientError, resp -> Mono.error(new IllegalStateException("2")))
+				.bodyToMono(Void.class);
+
+		StepVerifier.create(result).expectErrorMessage("2").verify();
+	}
+
 	@Test // gh-23880
 	@SuppressWarnings("unchecked")
 	public void onStatusHandlersDefaultHandlerIsLast() {