INT-4117: File Outbound Set File Permissions

JIRA: https://jira.spring.io/browse/INT-4117

Add an option to set file permissions on the `FileWritingMessageHandler` when the file system supports it.

Polishing - PR Comments; more robust file system detection.

Add DSL support and fix NPE with missing timestamp header.

Fix javadoc

Fix javadoc

Some polishing:

* Add `chmod >= 0` assertion
* Make some assertion with string concatenation as `Supplier`-based to
deffer that string concatenation

spring-integration-file/src/test/java/org/springframework/integration/file/FileWritingMessageHandlerTests.java

@@ -46,7 +46,10 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.attribute.PosixFilePermission;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.regex.Matcher;
@@ -61,9 +64,11 @@ import org.junit.rules.TemporaryFolder;
 
 import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.beans.factory.BeanFactory;
+import org.springframework.expression.Expression;
 import org.springframework.integration.channel.NullChannel;
 import org.springframework.integration.channel.QueueChannel;
 import org.springframework.integration.file.support.FileExistsMode;
+import org.springframework.integration.file.support.FileUtils;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.integration.test.util.TestUtils;
 import org.springframework.messaging.Message;
@@ -123,10 +128,40 @@ public class FileWritingMessageHandlerTests {
 	}
 
 	@Test
-	public void supportedType() throws Exception {
+	public void permissions() {
+		if (FileUtils.IS_POSIX) {
+			FileWritingMessageHandler handler = new FileWritingMessageHandler(mock(Expression.class));
+			handler.setChmod(0421);
+			Set<?> permissions = TestUtils.getPropertyValue(handler, "permissions", Set.class);
+			assertThat(permissions.size(), equalTo(3));
+			assertTrue(permissions.contains(PosixFilePermission.OWNER_READ));
+			assertTrue(permissions.contains(PosixFilePermission.GROUP_WRITE));
+			assertTrue(permissions.contains(PosixFilePermission.OTHERS_EXECUTE));
+			handler.setChmod(0600);
+			permissions = TestUtils.getPropertyValue(handler, "permissions", Set.class);
+			assertThat(permissions.size(), equalTo(2));
+			assertTrue(permissions.contains(PosixFilePermission.OWNER_READ));
+			assertTrue(permissions.contains(PosixFilePermission.OWNER_WRITE));
+			handler.setChmod(0777);
+			permissions = TestUtils.getPropertyValue(handler, "permissions", Set.class);
+			assertThat(permissions.size(), equalTo(9));
+		}
+	}
+
+	@Test
+	public void supportedTypeAndPermissions() throws Exception {
+		if (FileUtils.IS_POSIX) {
+			handler.setChmod(0777);
+		}
 		handler.setOutputChannel(new NullChannel());
 		handler.handleMessage(new GenericMessage<String>("test"));
-		assertThat(outputDirectory.listFiles()[0], notNullValue());
+		File[] output = outputDirectory.listFiles();
+		assertThat(output.length, equalTo(1));
+		assertThat(output[0], notNullValue());
+		if (FileUtils.IS_POSIX) {
+			Set<PosixFilePermission> permissions = Files.getPosixFilePermissions(output[0].toPath());
+			assertThat(permissions.size(), equalTo(9));
+		}
 	}
 
 	@Test

spring-integration-file/src/test/java/org/springframework/integration/file/config/FileOutboundChannelAdapterParserTests-context.xml

@@ -17,6 +17,7 @@
 								   channel="testChannel"
 								   directory="${java.io.tmpdir}"
 								   temporary-file-suffix=".foo"
+								   chmod="777"
 								   filename-generator-expression="'foo.txt'"/>
 
 	<file:outbound-channel-adapter id="adapterWithCustomNameGenerator"

spring-integration-file/src/test/java/org/springframework/integration/file/config/FileOutboundChannelAdapterParserTests.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.file.config;
 
 import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
@@ -26,6 +27,7 @@ import static org.junit.Assert.assertTrue;
 import java.io.File;
 import java.lang.reflect.Method;
 import java.nio.charset.Charset;
+import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
@@ -41,6 +43,7 @@ import org.springframework.integration.file.DefaultFileNameGenerator;
 import org.springframework.integration.file.FileWritingMessageHandler;
 import org.springframework.integration.file.FileWritingMessageHandler.MessageFlushPredicate;
 import org.springframework.integration.file.support.FileExistsMode;
+import org.springframework.integration.file.support.FileUtils;
 import org.springframework.integration.handler.advice.AbstractRequestHandlerAdvice;
 import org.springframework.integration.test.util.TestUtils;
 import org.springframework.messaging.Message;
@@ -140,6 +143,9 @@ public class FileOutboundChannelAdapterParserTests {
 		assertEquals("'foo.txt'", expression.getExpressionString());
 		assertEquals(Boolean.FALSE, handlerAccessor.getPropertyValue("deleteSourceFiles"));
 		assertEquals(Boolean.TRUE, handlerAccessor.getPropertyValue("flushWhenIdle"));
+		if (FileUtils.IS_POSIX) {
+			assertThat(TestUtils.getPropertyValue(handler, "permissions", Set.class).size(), equalTo(9));
+		}
 	}
 
 	@Test

spring-integration-file/src/test/java/org/springframework/integration/file/dsl/FileTests.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.file.dsl;
 
 import static org.hamcrest.Matchers.endsWith;
+import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
@@ -74,6 +75,7 @@ import org.springframework.integration.file.filters.ChainFileListFilter;
 import org.springframework.integration.file.filters.ExpressionFileListFilter;
 import org.springframework.integration.file.splitter.FileSplitter;
 import org.springframework.integration.file.support.FileExistsMode;
+import org.springframework.integration.file.support.FileUtils;
 import org.springframework.integration.file.tail.ApacheCommonsFileTailingMessageProducer;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.integration.test.util.TestUtils;
@@ -240,6 +242,9 @@ public class FileTests {
 				endsWith(TestUtils.applySystemFileSeparator("fileWritingFlow/foo.write")));
 		String fileContent = StreamUtils.copyToString(new FileInputStream(resultFile), Charset.defaultCharset());
 		assertEquals(payload, fileContent);
+		if (FileUtils.IS_POSIX) {
+			assertThat(java.nio.file.Files.getPosixFilePermissions(resultFile.toPath()).size(), equalTo(9));
+		}
 	}
 
 	@Autowired
@@ -389,7 +394,9 @@ public class FileTests {
 			return IntegrationFlows.from("fileWritingInput")
 					.enrichHeaders(h -> h.header(FileHeaders.FILENAME, "foo.write")
 							.header("directory", new File(tmpDir.getRoot(), "fileWritingFlow")))
-					.handle(Files.outboundGateway(m -> m.getHeaders().get("directory")))
+					.handle(Files.outboundGateway(m -> m.getHeaders().get("directory"))
+							.preserveTimestamp(true)
+							.chmod(0777))
 					.channel(MessageChannels.queue("fileWritingResultChannel"))
 					.get();
 		}