Clear lock cache in NioFileLocker (#2998)

Fixes #2980
# Conflicts:
#	spring-integration-file/src/test/java/org/springframework/integration/file/locking/NioFileLockerTests.java

Author: garyrussell

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

@@ -34,7 +34,7 @@
  */
 final class FileChannelCache {
 
-	private static ConcurrentMap<File, FileChannel> channelCache = new ConcurrentHashMap<File, FileChannel>();
+	private static ConcurrentMap<File, FileChannel> channelCache = new ConcurrentHashMap<>();
 
 
 	private FileChannelCache() {

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

@@ -39,7 +39,7 @@
  */
 public class NioFileLocker extends AbstractFileLockerFilter {
 
-	private final ConcurrentMap<File, FileLock> lockCache = new ConcurrentHashMap<File, FileLock>();
+	private final ConcurrentMap<File, FileLock> lockCache = new ConcurrentHashMap<>();
 
 	@Override
 	public boolean lock(File fileToLock) {
@@ -67,7 +67,7 @@ public boolean isLockable(File file) {
 
 	@Override
 	public void unlock(File fileToUnlock) {
-		FileLock fileLock = this.lockCache.get(fileToUnlock);
+		FileLock fileLock = this.lockCache.remove(fileToUnlock);
 		try {
 			if (fileLock != null) {
 				fileLock.release();

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

@@ -18,20 +18,24 @@
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
 import java.io.File;
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.util.ArrayList;
-import java.util.List;
+import java.util.Map;
 
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
 import org.springframework.integration.file.filters.FileListFilter;
+import org.springframework.integration.test.util.TestUtils;
 
 /**
  * @author Iwein Fuld
+ * @author Gary Russell
  */
 public class NioFileLockerTests {
 
@@ -48,13 +52,18 @@ public void create() throws IOException {
 	};
 
 	@Test
-	public void fileListedByFirstFilter() throws IOException {
+	public void fileListedByFirstFilter() throws Exception {
 		NioFileLocker filter = new NioFileLocker();
 		File testFile = new File(workdir, "test0");
 		testFile.createNewFile();
 		assertThat(filter.filterFiles(workdir.listFiles()).get(0), is(testFile));
 		filter.lock(testFile);
 		assertThat(filter.filterFiles(workdir.listFiles()).get(0), is(testFile));
+		filter.unlock(testFile);
+		Field channelCache = FileChannelCache.class.getDeclaredField("channelCache");
+		channelCache.setAccessible(true);
+		assertTrue(((Map<?, ?>) channelCache.get(null)).isEmpty());
+		assertTrue(TestUtils.getPropertyValue(filter, "lockCache", Map.class).isEmpty());
 	}
 
 	@Test
@@ -65,7 +74,8 @@ public void fileNotListedWhenLockedByOtherFilter() throws IOException {
 		testFile.createNewFile();
 		assertThat(filter1.filterFiles(workdir.listFiles()).get(0), is(testFile));
 		filter1.lock(testFile);
-		assertThat(filter2.filterFiles(workdir.listFiles()), is((List<File>) new ArrayList<File>()));
+		assertThat(filter2.filterFiles(workdir.listFiles()), is(new ArrayList<File>()));
+		filter1.unlock(testFile);
 	}
 
 }