INT-4334: Adds a DirectoryScanner to RemoteFileMS

JIRA: https://jira.springsource.org/browse/INT-4334

* Add a `DirectoryScanner` setter named `setScanner` in
`AbstractInboundFileSynchronizingMessageSource` to set the
`FileReadingMessageSource`'s scanner.
* Add tests to `AbstractRemoteFileSynchronizerTests`.

Polish.

Updates xsd, tests and documentation.

Fix xsd formatting.

Addresses review comments.

* Some code style polishing

spring-integration-file/src/main/java/org/springframework/integration/file/config/AbstractRemoteFileInboundChannelAdapterParser.java

@@ -37,6 +37,7 @@ import org.springframework.util.StringUtils;
  * @author Mark Fisher
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Venil Noronha
  *
  * @since 2.0
  */
@@ -75,6 +76,7 @@ public abstract class AbstractRemoteFileInboundChannelAdapterParser extends Abst
 			messageSourceBuilder.addConstructorArgReference(comparator);
 		}
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(messageSourceBuilder, element, "local-filter");
+		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(messageSourceBuilder, element, "scanner");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(messageSourceBuilder, element, "local-directory");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(messageSourceBuilder, element,
 				"auto-create-local-directory");

spring-integration-file/src/main/java/org/springframework/integration/file/remote/synchronizer/AbstractInboundFileSynchronizingMessageSource.java

@@ -26,6 +26,7 @@ import java.util.regex.Pattern;
 import org.springframework.beans.factory.BeanInitializationException;
 import org.springframework.context.Lifecycle;
 import org.springframework.integration.endpoint.AbstractFetchLimitingMessageSource;
+import org.springframework.integration.file.DirectoryScanner;
 import org.springframework.integration.file.FileReadingMessageSource;
 import org.springframework.integration.file.RecursiveDirectoryScanner;
 import org.springframework.integration.file.filters.AcceptOnceFileListFilter;
@@ -59,6 +60,7 @@ import org.springframework.util.Assert;
  * @author Oleg Zhurakousky
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Venil Noronha
  */
 public abstract class AbstractInboundFileSynchronizingMessageSource<F>
 		extends AbstractFetchLimitingMessageSource<File> implements Lifecycle {
@@ -88,6 +90,10 @@ public abstract class AbstractInboundFileSynchronizingMessageSource<F>
 
 	private volatile FileListFilter<File> localFileListFilter;
 
+	/**
+	 * Whether the {@link DirectoryScanner} was explicitly set.
+	 */
+	private volatile boolean scannerExplicitlySet = false;
 
 	public AbstractInboundFileSynchronizingMessageSource(AbstractInboundFileSynchronizer<F> synchronizer) {
 		this(synchronizer, null);
@@ -145,6 +151,17 @@ public abstract class AbstractInboundFileSynchronizingMessageSource<F>
 		}
 	}
 
+	/**
+	 * Switch the local {@link FileReadingMessageSource} to use a custom
+	 * {@link DirectoryScanner}.
+	 * @param scanner the {@link DirectoryScanner} to use.
+	 * @since 5.0
+	 */
+	public void setScanner(DirectoryScanner scanner) {
+		this.fileSource.setScanner(scanner);
+		this.scannerExplicitlySet = true;
+	}
+
 	@Override
 	public void afterPropertiesSet() throws Exception {
 		super.afterPropertiesSet();
@@ -167,7 +184,12 @@ public abstract class AbstractInboundFileSynchronizingMessageSource<F>
 						new SimpleMetadataStore(), getComponentName());
 			}
 			FileListFilter<File> filter = buildFilter();
-			if (!this.fileSource.isUseWatchService()) {
+			if (this.scannerExplicitlySet) {
+				Assert.state(!this.fileSource.isUseWatchService(),
+						"'useWatchService' and 'scanner' are mutually exclusive.");
+				this.fileSource.getScanner().setFilter(filter);
+			}
+			else if (!this.fileSource.isUseWatchService()) {
 				RecursiveDirectoryScanner directoryScanner = new RecursiveDirectoryScanner();
 				directoryScanner.setFilter(filter);
 				this.fileSource.setScanner(directoryScanner);

spring-integration-file/src/test/java/org/springframework/integration/file/remote/synchronizer/AbstractRemoteFileSynchronizerTests.java

@@ -33,6 +33,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import org.junit.Test;
 
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.integration.file.HeadDirectoryScanner;
 import org.springframework.integration.file.filters.AcceptOnceFileListFilter;
 import org.springframework.integration.file.remote.session.Session;
 import org.springframework.integration.file.remote.session.SessionFactory;
@@ -41,6 +42,7 @@ import org.springframework.messaging.MessagingException;
 /**
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Venil Noronha
  *
  * @since 4.0.4
  *
@@ -116,21 +118,7 @@ public class AbstractRemoteFileSynchronizerTests {
 	public void testMaxFetchSizeSource() throws Exception {
 		final AtomicInteger count = new AtomicInteger();
 		AbstractInboundFileSynchronizer<String> sync = createLimitingSynchronizer(count);
-
-		AbstractInboundFileSynchronizingMessageSource<String> source =
-				new AbstractInboundFileSynchronizingMessageSource<String>(sync) {
-
-			@Override
-			public String getComponentType() {
-				return "foo";
-			}
-
-		};
-		source.setLocalDirectory(new File(System.getProperty("java.io.tmpdir") + File.separator + UUID.randomUUID()));
-		source.setAutoCreateLocalDirectory(true);
-		source.setBeanFactory(mock(BeanFactory.class));
-		source.setMaxFetchSize(1);
-		source.setBeanName("maxFetchSizeSource");
+		AbstractInboundFileSynchronizingMessageSource<String> source = createSource(sync);
 		source.afterPropertiesSet();
 		source.start();
 
@@ -143,6 +131,60 @@ public class AbstractRemoteFileSynchronizerTests {
 		source.stop();
 	}
 
+	@Test
+	public void testExclusiveScanner() throws Exception {
+		final AtomicInteger count = new AtomicInteger();
+		AbstractInboundFileSynchronizingMessageSource<String> source = createSource(count);
+		source.setScanner(new HeadDirectoryScanner(1));
+		source.afterPropertiesSet();
+		source.start();
+		source.receive();
+		assertEquals(1, count.get());
+	}
+
+	@Test
+	public void testExclusiveWatchService() throws Exception {
+		final AtomicInteger count = new AtomicInteger();
+		AbstractInboundFileSynchronizingMessageSource<String> source = createSource(count);
+		source.setUseWatchService(true);
+		source.afterPropertiesSet();
+		source.start();
+		source.receive();
+		assertEquals(1, count.get());
+	}
+
+	@Test(expected = IllegalStateException.class)
+	public void testScannerAndWatchServiceConflict() throws Exception {
+		final AtomicInteger count = new AtomicInteger();
+		AbstractInboundFileSynchronizingMessageSource<String> source = createSource(count);
+		source.setUseWatchService(true);
+		source.setScanner(new HeadDirectoryScanner(1));
+		source.afterPropertiesSet();
+	}
+
+	private AbstractInboundFileSynchronizingMessageSource<String> createSource(AtomicInteger count) {
+		return createSource(createLimitingSynchronizer(count));
+	}
+
+	private AbstractInboundFileSynchronizingMessageSource<String> createSource(
+			AbstractInboundFileSynchronizer<String> sync) {
+		AbstractInboundFileSynchronizingMessageSource<String> source =
+				new AbstractInboundFileSynchronizingMessageSource<String>(sync) {
+
+					@Override
+					public String getComponentType() {
+						return "foo";
+					}
+
+				};
+		source.setMaxFetchSize(1);
+		source.setLocalDirectory(new File(System.getProperty("java.io.tmpdir") + File.separator + UUID.randomUUID()));
+		source.setAutoCreateLocalDirectory(true);
+		source.setBeanFactory(mock(BeanFactory.class));
+		source.setBeanName("fooSource");
+		return source;
+	}
+
 	private AbstractInboundFileSynchronizer<String> createLimitingSynchronizer(final AtomicInteger count) {
 		SessionFactory<String> sf = new StringSessionFactory();
 		AbstractInboundFileSynchronizer<String> sync = new AbstractInboundFileSynchronizer<String>(sf) {
@@ -194,7 +236,7 @@ public class AbstractRemoteFileSynchronizerTests {
 
 		@Override
 		public String[] list(String path) throws IOException {
-			return new String[] {"foo", "bar", "baz"};
+			return new String[] { "foo", "bar", "baz" };
 		}
 
 		@Override