GH-3076: Add file existence check

Fixes #3076

Author: EmmanuelRoux

spring-integration-file/src/main/java/org/springframework/integration/file/locking/FileChannelCache.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.file.locking;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.channels.FileChannel;
@@ -30,6 +31,7 @@
  *
  * @author Iwein Fuld
  * @author Gary Russell
+ * @author Emmanuel Roux
  * @since 2.0
  */
 final class FileChannelCache {
@@ -43,13 +45,18 @@ private FileChannelCache() {
 
 	/**
 	 * Try to get a lock for this file while guaranteeing that the same channel will be used for all file locks in this
-	 * VM. If the lock could not be acquired this method will return <code>null</code>.
+	 * VM. If the lock could not be acquired this method will return <code>null</code>. If the file does not exist this
+	 * method will throw a {@link FileNotFoundException}.
 	 * <p>
 	 * Locks acquired through this method should be passed back to #closeChannelFor to prevent memory leaks.
 	 * <p>
 	 * Thread safe.
 	 */
 	public static FileLock tryLockFor(File fileToLock) throws IOException {
+		if (!fileToLock.exists()) {
+			throw new FileNotFoundException("Unable to get lock for non-existent file: " + fileToLock.getAbsolutePath());
+		}
+
 		FileChannel channel = channelCache.get(fileToLock);
 		if (channel == null) {
 			@SuppressWarnings("resource")

spring-integration-file/src/main/java/org/springframework/integration/file/locking/NioFileLocker.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.file.locking;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.channels.FileLock;
 import java.util.concurrent.ConcurrentHashMap;
@@ -36,6 +37,7 @@
  * @author Iwein Fuld
  * @author Mark Fisher
  * @author Gary Russell
+ * @author Emmanuel Roux
  * @since 2.0
  */
 public class NioFileLocker extends AbstractFileLockerFilter {
@@ -50,6 +52,9 @@ public boolean lock(File fileToLock) {
 			try {
 				newLock = FileChannelCache.tryLockFor(fileToLock);
 			}
+			catch (FileNotFoundException e) {
+				// Consider lock failed
+			}
 			catch (IOException e) {
 				throw new MessagingException("Failed to lock file: " + fileToLock, e);
 			}

spring-integration-file/src/test/java/org/springframework/integration/file/locking/FileChannelCacheTests.java

@@ -0,0 +1,62 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.file.locking;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.channels.FileLock;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+/**
+ * @author Emmanuel Roux
+ */
+public class FileChannelCacheTests {
+
+	private File workdir;
+
+	@Rule
+	public TemporaryFolder temp = new TemporaryFolder() {
+
+		@Override
+		public void create() throws IOException {
+			super.create();
+			workdir = temp.newFolder(FileChannelCacheTests.class.getSimpleName());
+		}
+	};
+
+	@Test(expected = FileNotFoundException.class)
+	public void throwsExceptionWhenFileNotExists() throws IOException {
+		File testFile = new File(workdir, "test0");
+		assertThat(testFile.exists()).isFalse();
+		FileChannelCache.tryLockFor(testFile);
+	}
+
+	@Test
+	public void fileLocked() throws IOException {
+		File testFile = new File(workdir, "test1");
+		testFile.createNewFile();
+		assertThat(testFile.exists()).isTrue();
+		assertThat(FileChannelCache.tryLockFor(testFile)).isNotNull();
+		FileChannelCache.closeChannelFor(testFile);
+	}
+}

spring-integration-file/src/test/java/org/springframework/integration/file/locking/NioFileLockerTests.java

@@ -34,6 +34,7 @@
 /**
  * @author Iwein Fuld
  * @author Gary Russell
+ * @author Emmanuel Roux
  */
 public class NioFileLockerTests {
 
@@ -76,4 +77,20 @@ public void fileNotListedWhenLockedByOtherFilter() throws IOException {
 		filter1.unlock(testFile);
 	}
 
+	@Test
+	public void fileLockedWhenNotAlreadyLockedAndExists() throws IOException {
+		NioFileLocker locker = new NioFileLocker();
+		File testFile = new File(workdir, "test2");
+		testFile.createNewFile();
+		assertThat(locker.lock(testFile)).isTrue();
+		locker.unlock(testFile);
+	}
+
+	@Test
+	public void fileNotLockedWhenNotExists() throws IOException {
+		NioFileLocker locker = new NioFileLocker();
+		File testFile = new File(workdir, "test3");
+		assertThat(locker.lock(testFile)).isFalse();
+		assertThat(testFile.exists()).isFalse();
+	}
 }