Provide access to raw content in RestTestClient

Closes gh-35399

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClient.java

@@ -16,12 +16,14 @@
 
 package org.springframework.test.web.servlet.client;
 
+import java.io.IOException;
 import java.net.URI;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.time.ZonedDateTime;
 import java.util.Map;
 import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -33,13 +35,18 @@ import org.jspecify.annotations.Nullable;
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpRequest;
 import org.springframework.http.MediaType;
+import org.springframework.http.client.ClientHttpRequestExecution;
+import org.springframework.http.client.ClientHttpRequestInterceptor;
+import org.springframework.http.client.ClientHttpResponse;
 import org.springframework.test.json.JsonAssert;
 import org.springframework.test.json.JsonComparator;
 import org.springframework.test.json.JsonCompareMode;
 import org.springframework.test.util.AssertionErrors;
 import org.springframework.test.util.ExceptionCollector;
 import org.springframework.test.util.XmlExpectationsHelper;
+import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.client.RestClient;
@@ -56,6 +63,8 @@ class DefaultRestTestClient implements RestTestClient {
 
 	private final RestClient restClient;
 
+	private final WiretapInterceptor wiretapInterceptor = new WiretapInterceptor();
+
 	private final Consumer<EntityExchangeResult<?>> entityResultConsumer;
 
 	private final DefaultRestTestClientBuilder<?> restTestClientBuilder;
@@ -67,7 +76,7 @@ class DefaultRestTestClient implements RestTestClient {
 			RestClient.Builder builder, Consumer<EntityExchangeResult<?>> entityResultConsumer,
 			DefaultRestTestClientBuilder<?> restTestClientBuilder) {
 
-		this.restClient = builder.build();
+		this.restClient = builder.requestInterceptor(this.wiretapInterceptor).build();
 		this.entityResultConsumer = entityResultConsumer;
 		this.restTestClientBuilder = restTestClientBuilder;
 	}
@@ -128,12 +137,14 @@ class DefaultRestTestClient implements RestTestClient {
 
 		private final RestClient.RequestBodyUriSpec requestHeadersUriSpec;
 
+		private final String requestId;
+
 		private @Nullable String uriTemplate;
 
 		DefaultRequestBodyUriSpec(RestClient.RequestBodyUriSpec spec) {
 			this.requestHeadersUriSpec = spec;
-			String requestId = String.valueOf(requestIndex.incrementAndGet());
-			this.requestHeadersUriSpec.header(RESTTESTCLIENT_REQUEST_ID, requestId);
+			this.requestId = String.valueOf(requestIndex.incrementAndGet());
+			this.requestHeadersUriSpec.header(RESTTESTCLIENT_REQUEST_ID, this.requestId);
 		}
 
 		@Override
@@ -252,7 +263,10 @@ class DefaultRestTestClient implements RestTestClient {
 		public ResponseSpec exchange() {
 			return new DefaultResponseSpec(
 					this.requestHeadersUriSpec.exchangeForRequiredValue(
-							(request, response) -> new ExchangeResult(request, response, this.uriTemplate), false),
+							(request, response) -> {
+								byte[] requestBody = wiretapInterceptor.getRequestContent(this.requestId);
+								return new ExchangeResult(request, response, this.uriTemplate, requestBody);
+							}, false),
 					DefaultRestTestClient.this.entityResultConsumer);
 		}
 	}
@@ -476,4 +490,29 @@ class DefaultRestTestClient implements RestTestClient {
 			return this.result;
 		}
 	}
+
+
+	private static class WiretapInterceptor implements ClientHttpRequestInterceptor {
+
+		private final Map<String, byte[]> requestContentMap = new ConcurrentHashMap<>();
+
+		@Override
+		public ClientHttpResponse intercept(
+				HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
+
+			String header = RestTestClient.RESTTESTCLIENT_REQUEST_ID;
+			String requestId = request.getHeaders().getFirst(header);
+			Assert.state(requestId != null, () -> "No \"" + header + "\" header");
+			this.requestContentMap.put(requestId, body);
+			return execution.execute(request, body);
+		}
+
+		public byte[] getRequestContent(String requestId) {
+			byte[] bytes = this.requestContentMap.remove(requestId);
+			Assert.state(bytes != null, () ->
+					"No match for %s=%s".formatted(RestTestClient.RESTTESTCLIENT_REQUEST_ID, requestId));
+			return bytes;
+		}
+	}
+
 }

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClientBuilder.java

@@ -61,7 +61,7 @@ class DefaultRestTestClientBuilder<B extends RestTestClient.Builder<B>> implemen
 	}
 
 	DefaultRestTestClientBuilder(RestClient.Builder restClientBuilder) {
-		this.restClientBuilder = restClientBuilder;
+		this.restClientBuilder = restClientBuilder.bufferContent((uri, httpMethod) -> true);
 	}
 
 	DefaultRestTestClientBuilder(DefaultRestTestClientBuilder<B> other) {

spring-test/src/main/java/org/springframework/test/web/servlet/client/ExchangeResult.java

@@ -19,6 +19,8 @@ package org.springframework.test.web.servlet.client;
 import java.io.IOException;
 import java.net.HttpCookie;
 import java.net.URI;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Optional;
 import java.util.regex.Matcher;
@@ -34,10 +36,12 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRequest;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.HttpStatusCode;
+import org.springframework.http.MediaType;
 import org.springframework.http.ResponseCookie;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
+import org.springframework.util.StreamUtils;
 import org.springframework.web.client.RestClient.RequestHeadersSpec.ConvertibleClientHttpResponse;
 
 /**
@@ -54,6 +58,10 @@ public class ExchangeResult {
 
 	private static final Pattern PARTITIONED_PATTERN = Pattern.compile("(?i).*;\\s*Partitioned(\\s*;.*|\\s*)$");
 
+	private static final List<MediaType> PRINTABLE_MEDIA_TYPES = List.of(
+			MediaType.parseMediaType("application/*+json"), MediaType.APPLICATION_XML,
+			MediaType.parseMediaType("text/*"), MediaType.APPLICATION_FORM_URLENCODED);
+
 
 	private static final Log logger = LogFactory.getLog(ExchangeResult.class);
 
@@ -64,22 +72,26 @@ public class ExchangeResult {
 
 	private final @Nullable String uriTemplate;
 
+	private final byte[] requestBody;
+
 	/** Ensure single logging; for example, for expectAll. */
 	private boolean diagnosticsLogged;
 
 
 	ExchangeResult(
-			HttpRequest request, ConvertibleClientHttpResponse response, @Nullable String uriTemplate) {
+			HttpRequest request, ConvertibleClientHttpResponse response, @Nullable String uriTemplate,
+			byte[] requestBody) {
 
 		Assert.notNull(request, "HttpRequest must not be null");
 		Assert.notNull(response, "ClientHttpResponse must not be null");
 		this.request = request;
 		this.clientResponse = response;
 		this.uriTemplate = uriTemplate;
+		this.requestBody = requestBody;
 	}
 
 	ExchangeResult(ExchangeResult result) {
-		this(result.request, result.clientResponse, result.uriTemplate);
+		this(result.request, result.clientResponse, result.uriTemplate, result.requestBody);
 		this.diagnosticsLogged = result.diagnosticsLogged;
 	}
 
@@ -159,6 +171,13 @@ public class ExchangeResult {
 				.build();
 	}
 
+	/**
+	 * Return the raw request body content written through the request.
+	 */
+	public byte[] getRequestBodyContent() {
+		return this.requestBody;
+	}
+
 	/**
 	 * Provide access to the response. For internal use to decode the body.
 	 */
@@ -166,6 +185,18 @@ public class ExchangeResult {
 		return this.clientResponse;
 	}
 
+	/**
+	 * Return the raw response body read through the response.
+	 */
+	public byte[] getResponseBodyContent() {
+		try {
+			return StreamUtils.copyToByteArray(this.clientResponse.getBody());
+		}
+		catch (IOException ex) {
+			throw new IllegalStateException("Failed to get response content: " + ex);
+		}
+	}
+
 	/**
 	 * Execute the given Runnable, catch any {@link AssertionError}, log details
 	 * about the request and response at ERROR level under the class log
@@ -190,8 +221,12 @@ public class ExchangeResult {
 				"> " + getMethod() + " " + getUrl() + "\n" +
 				"> " + formatHeaders(getRequestHeaders(), "\n> ") + "\n" +
 				"\n" +
+				formatBody(getRequestHeaders().getContentType(), this.requestBody) + "\n" +
+				"\n" +
 				"< " + formatStatus(getStatus()) + "\n" +
-				"< " + formatHeaders(getResponseHeaders(), "\n< ") + "\n";
+				"< " + formatHeaders(getResponseHeaders(), "\n< ") + "\n" +
+				"\n" +
+				formatBody(getResponseHeaders().getContentType(), getResponseBodyContent()) +"\n";
 	}
 
 	private String formatStatus(HttpStatusCode statusCode) {
@@ -208,4 +243,18 @@ public class ExchangeResult {
 				.collect(Collectors.joining(delimiter));
 	}
 
+	private String formatBody(@Nullable MediaType contentType, byte[] bytes) {
+		if (contentType == null) {
+			return bytes.length + " bytes of content (unknown content-type).";
+		}
+		Charset charset = contentType.getCharset();
+		if (charset != null) {
+			return new String(bytes, charset);
+		}
+		if (PRINTABLE_MEDIA_TYPES.stream().anyMatch(contentType::isCompatibleWith)) {
+			return new String(bytes, StandardCharsets.UTF_8);
+		}
+		return bytes.length + " bytes of content.";
+	}
+
 }

spring-test/src/test/java/org/springframework/test/web/servlet/client/RestTestClientTests.java

@@ -36,6 +36,8 @@ import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -317,6 +319,19 @@ class RestTestClientTests {
 					});
 			assertThat(result.getResponseBody().get("uri")).isEqualTo("/test");
 		}
+
+		@Test
+		void testResultContent() {
+			String body = "body-in";
+			EntityExchangeResult<String> result = RestTestClientTests.this.client.post().uri("/body")
+					.body(body)
+					.exchange()
+					.expectStatus().isOk()
+					.expectBody(String.class)
+					.returnResult();
+			assertThat(result.getRequestBodyContent()).isEqualTo(body.getBytes(StandardCharsets.UTF_8));
+			assertThat(result.getResponseBodyContent()).isEqualTo((body + "-out").getBytes(StandardCharsets.UTF_8));
+		}
 	}
 
 
@@ -325,14 +340,20 @@ class RestTestClientTests {
 
 		@RequestMapping(path = {"/test", "/test/*"}, produces = "application/json")
 		public Map<String, Object> handle(
-				@RequestHeader HttpHeaders headers,
-				HttpServletRequest request, HttpServletResponse response) {
+				@RequestHeader HttpHeaders headers, HttpServletRequest request, HttpServletResponse response) {
+
 			response.addCookie(new Cookie("session", "abc"));
+
 			return Map.of(
 					"method", request.getMethod(),
 					"uri", request.getRequestURI(),
 					"headers", headers.toSingleValueMap()
 			);
 		}
+
+		@PostMapping("/body")
+		public String echoBody(@RequestBody String body) {
+			return body + "-out";
+		}
 	}
 }