Ensure Synchronoss temp directories do not collide

This commit makes sure that Synchronoss uses a random temporary
directory to store uploaded files, so that two instances do not collide.

Closes gh-26931

Author: poutsma

spring-web/src/main/java/org/springframework/http/codec/multipart/SynchronossPartHttpMessageReader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -17,11 +17,13 @@
 package org.springframework.http.codec.multipart;
 
 import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.channels.Channels;
 import java.nio.channels.FileChannel;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.nio.file.OpenOption;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
@@ -82,13 +84,17 @@ public class SynchronossPartHttpMessageReader extends LoggingCodecSupport implem
 	// Static DataBufferFactory to copy from FileInputStream or wrap bytes[].
 	private static final DataBufferFactory bufferFactory = new DefaultDataBufferFactory();
 
+	private static final String FILE_STORAGE_DIRECTORY_PREFIX = "synchronoss-file-upload-";
+
 
 	private int maxInMemorySize = 256 * 1024;
 
 	private long maxDiskUsagePerPart = -1;
 
 	private int maxParts = -1;
 
+	private Path fileStorageDirectory = createTempDirectory();
+
 
 	/**
 	 * Configure the maximum amount of memory that is allowed to use per part.
@@ -172,7 +178,7 @@ public boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType
 
 	@Override
 	public Flux<Part> read(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints) {
-		return Flux.create(new SynchronossPartGenerator(message))
+		return Flux.create(new SynchronossPartGenerator(message, this.fileStorageDirectory))
 				.doOnNext(part -> {
 					if (!Hints.isLoggingSuppressed(hints)) {
 						LogFormatUtils.traceDebug(logger, traceOn -> Hints.getLogPrefix(hints) + "Parsed " +
@@ -188,6 +194,15 @@ public Mono<Part> readMono(ResolvableType elementType, ReactiveHttpInputMessage
 		return Mono.error(new UnsupportedOperationException("Cannot read multipart request body into single Part"));
 	}
 
+	private static Path createTempDirectory() {
+		try {
+			return Files.createTempDirectory(FILE_STORAGE_DIRECTORY_PREFIX);
+		}
+		catch (IOException ex) {
+			throw new UncheckedIOException(ex);
+		}
+	}
+
 
 	/**
 	 * Subscribe to the input stream and feed the Synchronoss parser. Then listen
@@ -199,14 +214,17 @@ private class SynchronossPartGenerator extends BaseSubscriber<DataBuffer> implem
 
 		private final LimitedPartBodyStreamStorageFactory storageFactory = new LimitedPartBodyStreamStorageFactory();
 
+		private final Path fileStorageDirectory;
+
 		@Nullable
 		private NioMultipartParserListener listener;
 
 		@Nullable
 		private NioMultipartParser parser;
 
-		public SynchronossPartGenerator(ReactiveHttpInputMessage inputMessage) {
+		public SynchronossPartGenerator(ReactiveHttpInputMessage inputMessage, Path fileStorageDirectory) {
 			this.inputMessage = inputMessage;
+			this.fileStorageDirectory = fileStorageDirectory;
 		}
 
 		@Override
@@ -223,6 +241,7 @@ public void accept(FluxSink<Part> sink) {
 
 			this.parser = Multipart
 					.multipart(context)
+					.saveTemporaryFilesTo(this.fileStorageDirectory.toString())
 					.usePartBodyStreamStorageFactory(this.storageFactory)
 					.forNIO(this.listener);