Explicitly close InputStream after resolution in RequestPartMethodArgumentResolver

Closes gh-27773

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodArgumentResolver.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.
@@ -169,7 +169,7 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 		HttpMethod httpMethod = (inputMessage instanceof HttpRequest ? ((HttpRequest) inputMessage).getMethod() : null);
 		Object body = NO_VALUE;
 
-		EmptyBodyCheckingHttpInputMessage message;
+		EmptyBodyCheckingHttpInputMessage message = null;
 		try {
 			message = new EmptyBodyCheckingHttpInputMessage(inputMessage);
 
@@ -196,6 +196,11 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 		catch (IOException ex) {
 			throw new HttpMessageNotReadableException("I/O error while reading input message", ex, inputMessage);
 		}
+		finally {
+			if (message != null && message.hasBody()) {
+				closeStreamIfNecessary(message.getBody());
+			}
+		}
 
 		if (body == NO_VALUE) {
 			if (httpMethod == null || !SUPPORTED_METHODS.contains(httpMethod) ||
@@ -298,6 +303,15 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 		return arg;
 	}
 
+	/**
+	 * Allow for closing the body stream if necessary,
+	 * e.g. for part streams in a multipart request.
+	 */
+	void closeStreamIfNecessary(InputStream body) {
+		// No-op by default: A standard HttpInputMessage exposes the HTTP request stream
+		// (ServletRequest#getInputStream), with its lifecycle managed by the container.
+	}
+
 
 	private static class EmptyBodyCheckingHttpInputMessage implements HttpInputMessage {
 

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestPartMethodArgumentResolver.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.
@@ -16,6 +16,8 @@
 
 package org.springframework.web.servlet.mvc.method.annotation;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.util.List;
 
 import javax.servlet.http.HttpServletRequest;
@@ -180,4 +182,17 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageConverterM
 		return partName;
 	}
 
+	@Override
+	void closeStreamIfNecessary(InputStream body) {
+		// RequestPartServletServerHttpRequest exposes individual part streams,
+		// potentially from temporary files -> explicit close call after resolution
+		// in order to prevent file descriptor leaks.
+		try {
+			body.close();
+		}
+		catch (IOException ex) {
+			// ignore
+		}
+	}
+
 }

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestPartMethodArgumentResolverTests.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.
@@ -16,6 +16,9 @@
 
 package org.springframework.web.servlet.mvc.method.annotation;
 
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Method;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
@@ -83,6 +86,8 @@ public class RequestPartMethodArgumentResolverTests {
 
 	private MultipartFile multipartFile2;
 
+	private CloseTrackingInputStream trackedStream;
+
 	private MockMultipartHttpServletRequest multipartRequest;
 
 	private NativeWebRequest webRequest;
@@ -116,7 +121,14 @@ public class RequestPartMethodArgumentResolverTests {
 		reset(messageConverter);
 
 		byte[] content = "doesn't matter as long as not empty".getBytes(StandardCharsets.UTF_8);
-		multipartFile1 = new MockMultipartFile("requestPart", "", "text/plain", content);
+		multipartFile1 = new MockMultipartFile("requestPart", "", "text/plain", content) {
+			@Override
+			public InputStream getInputStream() throws IOException {
+				CloseTrackingInputStream in = new CloseTrackingInputStream(super.getInputStream());
+				trackedStream = in;
+				return in;
+			}
+		};
 		multipartFile2 = new MockMultipartFile("requestPart", "", "text/plain", content);
 		multipartRequest = new MockMultipartHttpServletRequest();
 		multipartRequest.addFile(multipartFile1);
@@ -182,8 +194,7 @@ public class RequestPartMethodArgumentResolverTests {
 	@Test
 	public void resolveMultipartFileList() throws Exception {
 		Object actual = resolver.resolveArgument(paramMultipartFileList, null, webRequest, null);
-		boolean condition = actual instanceof List;
-		assertThat(condition).isTrue();
+		assertThat(actual instanceof List).isTrue();
 		assertThat(actual).isEqualTo(Arrays.asList(multipartFile1, multipartFile2));
 	}
 
@@ -191,8 +202,7 @@ public class RequestPartMethodArgumentResolverTests {
 	public void resolveMultipartFileArray() throws Exception {
 		Object actual = resolver.resolveArgument(paramMultipartFileArray, null, webRequest, null);
 		assertThat(actual).isNotNull();
-		boolean condition = actual instanceof MultipartFile[];
-		assertThat(condition).isTrue();
+		assertThat(actual instanceof MultipartFile[]).isTrue();
 		MultipartFile[] parts = (MultipartFile[]) actual;
 		assertThat(parts.length).isEqualTo(2);
 		assertThat(multipartFile1).isEqualTo(parts[0]);
@@ -209,8 +219,7 @@ public class RequestPartMethodArgumentResolverTests {
 
 		Object result = resolver.resolveArgument(paramMultipartFileNotAnnot, null, webRequest, null);
 
-		boolean condition = result instanceof MultipartFile;
-		assertThat(condition).isTrue();
+		assertThat(result instanceof MultipartFile).isTrue();
 		assertThat(result).as("Invalid result").isEqualTo(expected);
 	}
 
@@ -225,8 +234,7 @@ public class RequestPartMethodArgumentResolverTests {
 		webRequest = new ServletWebRequest(request);
 
 		Object result = resolver.resolveArgument(paramPart, null, webRequest, null);
-		boolean condition = result instanceof Part;
-		assertThat(condition).isTrue();
+		assertThat(result instanceof Part).isTrue();
 		assertThat(result).as("Invalid result").isEqualTo(expected);
 	}
 
@@ -243,8 +251,7 @@ public class RequestPartMethodArgumentResolverTests {
 		webRequest = new ServletWebRequest(request);
 
 		Object result = resolver.resolveArgument(paramPartList, null, webRequest, null);
-		boolean condition = result instanceof List;
-		assertThat(condition).isTrue();
+		assertThat(result instanceof List).isTrue();
 		assertThat(result).isEqualTo(Arrays.asList(part1, part2));
 	}
 
@@ -261,8 +268,7 @@ public class RequestPartMethodArgumentResolverTests {
 		webRequest = new ServletWebRequest(request);
 
 		Object result = resolver.resolveArgument(paramPartArray, null, webRequest, null);
-		boolean condition = result instanceof Part[];
-		assertThat(condition).isTrue();
+		assertThat(result instanceof Part[]).isTrue();
 		Part[] parts = (Part[]) result;
 		assertThat(parts.length).isEqualTo(2);
 		assertThat(part1).isEqualTo(parts[0]);
@@ -357,8 +363,7 @@ public class RequestPartMethodArgumentResolverTests {
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(expected);
 
 		actualValue = resolver.resolveArgument(optionalMultipartFile, null, webRequest, null);
-		boolean condition = actualValue instanceof Optional;
-		assertThat(condition).isTrue();
+		assertThat(actualValue instanceof Optional).isTrue();
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(expected);
 	}
 
@@ -399,8 +404,7 @@ public class RequestPartMethodArgumentResolverTests {
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(Collections.singletonList(expected));
 
 		actualValue = resolver.resolveArgument(optionalMultipartFileList, null, webRequest, null);
-		boolean condition = actualValue instanceof Optional;
-		assertThat(condition).isTrue();
+		assertThat(actualValue instanceof Optional).isTrue();
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(Collections.singletonList(expected));
 	}
 
@@ -443,8 +447,7 @@ public class RequestPartMethodArgumentResolverTests {
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(expected);
 
 		actualValue = resolver.resolveArgument(optionalPart, null, webRequest, null);
-		boolean condition = actualValue instanceof Optional;
-		assertThat(condition).isTrue();
+		assertThat(actualValue instanceof Optional).isTrue();
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(expected);
 	}
 
@@ -489,8 +492,7 @@ public class RequestPartMethodArgumentResolverTests {
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(Collections.singletonList(expected));
 
 		actualValue = resolver.resolveArgument(optionalPartList, null, webRequest, null);
-		boolean condition = actualValue instanceof Optional;
-		assertThat(condition).isTrue();
+		assertThat(actualValue instanceof Optional).isTrue();
 		assertThat(((Optional<?>) actualValue).get()).as("Invalid result").isEqualTo(Collections.singletonList(expected));
 	}
 
@@ -572,6 +574,7 @@ public class RequestPartMethodArgumentResolverTests {
 		Object actualValue = resolver.resolveArgument(parameter, mavContainer, webRequest, new ValidatingBinderFactory());
 		assertThat(actualValue).as("Invalid argument value").isEqualTo(argValue);
 		assertThat(mavContainer.isRequestHandled()).as("The requestHandled flag shouldn't change").isFalse();
+		assertThat(trackedStream != null && trackedStream.closed).isTrue();
 	}
 
 
@@ -591,7 +594,7 @@ public class RequestPartMethodArgumentResolverTests {
 	}
 
 
-	private final class ValidatingBinderFactory implements WebDataBinderFactory {
+	private static class ValidatingBinderFactory implements WebDataBinderFactory {
 
 		@Override
 		public WebDataBinder createBinder(NativeWebRequest webRequest, @Nullable Object target,
@@ -606,6 +609,21 @@ public class RequestPartMethodArgumentResolverTests {
 	}
 
 
+	private static class CloseTrackingInputStream extends FilterInputStream {
+
+		public boolean closed = false;
+
+		public CloseTrackingInputStream(InputStream in) {
+			super(in);
+		}
+
+		@Override
+		public void close() {
+			this.closed = true;
+		}
+	}
+
+
 	@SuppressWarnings("unused")
 	public void handle(
 			@RequestPart SimpleBean requestPart,