Wrap DecodingException in DefaultServerRequest

Prior to this commit, Spring WebFlux function would let
`DecodingException` thrown by codecs bubble up to the web handler level.
Since this exception is not handled by default there, the response would
be turned into a HTTP 500 status.

In the annotation model, `ArgumentResolver` implementations wrap this
exception with a `ServerWebInputException`, which itself extends
`ResponseStatusException`. The latter is supported by the error handling
infrastructure as a HTTP 400 response.

This commit ensures that `DecodingException` instances are properly
wrapped in `ServerWebInputException` at the `ServerRequest` level
directly, thus supporting all setup modes ("standalone" and through the
`DispatcherHandler`).

Fixes #22290

Author: bclozel

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -33,6 +33,7 @@
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.codec.DecodingException;
 import org.springframework.core.codec.Hints;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
@@ -48,6 +49,7 @@
 import org.springframework.web.reactive.function.BodyExtractors;
 import org.springframework.web.reactive.function.UnsupportedMediaTypeException;
 import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.ServerWebInputException;
 import org.springframework.web.server.UnsupportedMediaTypeStatusException;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.util.UriBuilder;
@@ -67,6 +69,9 @@ class DefaultServerRequest implements ServerRequest {
 							ex.getContentType(), ex.getSupportedMediaTypes(), ex.getBodyType()) :
 					new UnsupportedMediaTypeStatusException(ex.getMessage()));
 
+	private static final Function<DecodingException, ServerWebInputException> DECODING_MAPPER =
+			ex -> new ServerWebInputException("Failed to read HTTP message", null, ex);
+
 
 	private final ServerWebExchange exchange;
 
@@ -154,25 +159,29 @@ public Map<String, Object> hints() {
 	@Override
 	public <T> Mono<T> bodyToMono(Class<? extends T> elementClass) {
 		Mono<T> mono = body(BodyExtractors.toMono(elementClass));
-		return mono.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER);
+		return mono.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER)
+				.onErrorMap(DecodingException.class, DECODING_MAPPER);
 	}
 
 	@Override
 	public <T> Mono<T> bodyToMono(ParameterizedTypeReference<T> typeReference) {
 		Mono<T> mono = body(BodyExtractors.toMono(typeReference));
-		return mono.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER);
+		return mono.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER)
+				.onErrorMap(DecodingException.class, DECODING_MAPPER);
 	}
 
 	@Override
 	public <T> Flux<T> bodyToFlux(Class<? extends T> elementClass) {
 		Flux<T> flux = body(BodyExtractors.toFlux(elementClass));
-		return flux.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER);
+		return flux.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER)
+				.onErrorMap(DecodingException.class, DECODING_MAPPER);
 	}
 
 	@Override
 	public <T> Flux<T> bodyToFlux(ParameterizedTypeReference<T> typeReference) {
 		Flux<T> flux = body(BodyExtractors.toFlux(typeReference));
-		return flux.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER);
+		return flux.onErrorMap(UnsupportedMediaTypeException.class, ERROR_MAPPER)
+				.onErrorMap(DecodingException.class, DECODING_MAPPER);
 	}
 
 	@Override

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/DefaultServerRequestTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -22,6 +22,7 @@
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -45,12 +46,14 @@
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.DecoderHttpMessageReader;
 import org.springframework.http.codec.HttpMessageReader;
+import org.springframework.http.codec.json.Jackson2JsonDecoder;
 import org.springframework.http.codec.multipart.FormFieldPart;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
 import org.springframework.mock.web.test.server.MockServerWebExchange;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
+import org.springframework.web.server.ServerWebInputException;
 import org.springframework.web.server.UnsupportedMediaTypeStatusException;
 
 import static org.junit.Assert.*;
@@ -61,7 +64,8 @@
  */
 public class DefaultServerRequestTests {
 
-	private final List<HttpMessageReader<?>> messageReaders = Collections.singletonList(
+	private final List<HttpMessageReader<?>> messageReaders = Arrays.asList(
+			new DecoderHttpMessageReader<>(new Jackson2JsonDecoder()),
 			new DecoderHttpMessageReader<>(StringDecoder.allMimeTypes()));
 
 
@@ -279,6 +283,28 @@ public void bodyToMonoParameterizedTypeReference() {
 		assertEquals("foo", resultMono.block());
 	}
 
+	@Test
+	public void bodyToMonoDecodingException() {
+		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+		DefaultDataBuffer dataBuffer =
+				factory.wrap(ByteBuffer.wrap("{\"invalid\":\"json\" ".getBytes(StandardCharsets.UTF_8)));
+		Flux<DataBuffer> body = Flux.just(dataBuffer);
+
+		HttpHeaders httpHeaders = new HttpHeaders();
+		httpHeaders.setContentType(MediaType.APPLICATION_JSON);
+		MockServerHttpRequest mockRequest = MockServerHttpRequest
+				.method(HttpMethod.POST, "http://example.com/invalid")
+				.headers(httpHeaders)
+				.body(body);
+		DefaultServerRequest request = new DefaultServerRequest(MockServerWebExchange.from(mockRequest), messageReaders);
+
+		Mono<Map<String, String>> resultMono = request.bodyToMono(
+				new ParameterizedTypeReference<Map<String, String>>() {});
+		StepVerifier.create(resultMono)
+				.expectError(ServerWebInputException.class)
+				.verify();
+	}
+
 	@Test
 	public void bodyToFlux() {
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();