GH-3247: Fix SftpSession.exists for error code (#3248)

* GH-3247: Fix `SftpSession.exists` for error code

Fixes #3247

When there is no path on the SFTP server, a `ChannelSftp.SSH_FX_NO_SUCH_FILE`
error is returned in the thrown `SftpException`.

* Fix `SftpSession.exists()` to check for the `SSH_FX_NO_SUCH_FILE` to
return `false` and re-throw an exception otherwise
* Add mock test for `SftpSession.exists()`
* Add `org.mockito.AdditionalMatchers` to `checkstyle.xml` exclusions

**Cherry-pick to 5.2.x & 5.1.x**

* * Add exists tests against Mina embedded server

Author: artembilan

spring-integration-sftp/src/main/java/org/springframework/integration/sftp/session/SftpSession.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -19,6 +19,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.UncheckedIOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Vector;
@@ -108,16 +109,15 @@ public LsEntry[] list(String path) throws IOException {
 	@Override
 	public String[] listNames(String path) throws IOException {
 		LsEntry[] entries = this.list(path);
-		List<String> names = new ArrayList<String>();
-		for (int i = 0; i < entries.length; i++) {
-			String fileName = entries[i].getFilename();
-			SftpATTRS attrs = entries[i].getAttrs();
+		List<String> names = new ArrayList<>();
+		for (LsEntry entry : entries) {
+			String fileName = entry.getFilename();
+			SftpATTRS attrs = entry.getAttrs();
 			if (!attrs.isDir() && !attrs.isLink()) {
 				names.add(fileName);
 			}
 		}
-		String[] fileNames = new String[names.size()];
-		return names.toArray(fileNames);
+		return names.toArray(new String[0]);
 	}
 
 
@@ -251,10 +251,15 @@ public boolean exists(String path) {
 			this.channel.lstat(path);
 			return true;
 		}
-		catch (SftpException e) {
-			// ignore
+		catch (SftpException ex) {
+			if (ex.id == ChannelSftp.SSH_FX_NO_SUCH_FILE) {
+				return false;
+			}
+			else {
+				throw new UncheckedIOException("Cannot check 'lstat' for path " + path,
+						new IOException(ex));
+			}
 		}
-		return false;
 	}
 
 	void connect() {

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpOutboundTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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 +17,16 @@
 package org.springframework.integration.sftp.outbound;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.BDDMockito.willAnswer;
+import static org.mockito.BDDMockito.willReturn;
+import static org.mockito.BDDMockito.willThrow;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
@@ -32,15 +37,17 @@
 
 import java.io.File;
 import java.io.FileOutputStream;
+import java.io.IOException;
 import java.io.InputStream;
+import java.io.UncheckedIOException;
 import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Vector;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
 
 import org.springframework.beans.DirectFieldAccessor;
@@ -69,6 +76,7 @@
 import com.jcraft.jsch.JSch;
 import com.jcraft.jsch.JSchException;
 import com.jcraft.jsch.SftpATTRS;
+import com.jcraft.jsch.SftpException;
 
 /**
  * @author Oleg Zhurakousky
@@ -78,15 +86,15 @@
  */
 public class SftpOutboundTests {
 
-	private static com.jcraft.jsch.Session jschSession = mock(com.jcraft.jsch.Session.class);
+	private static final com.jcraft.jsch.Session jschSession = mock(com.jcraft.jsch.Session.class);
 
 	@Test
 	public void testHandleFileMessage() throws Exception {
 		File targetDir = new File("remote-target-dir");
 		assertTrue("target directory does not exist: " + targetDir.getName(), targetDir.exists());
 
 		SessionFactory<LsEntry> sessionFactory = new TestSftpSessionFactory();
-		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<LsEntry>(sessionFactory);
+		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<>(sessionFactory);
 		handler.setRemoteDirectoryExpression(new LiteralExpression(targetDir.getName()));
 		DefaultFileNameGenerator fGenerator = new DefaultFileNameGenerator();
 		fGenerator.setBeanFactory(mock(BeanFactory.class));
@@ -135,7 +143,7 @@ public void testHandleBytesMessage() throws Exception {
 			file.delete();
 		}
 		SessionFactory<LsEntry> sessionFactory = new TestSftpSessionFactory();
-		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<LsEntry>(sessionFactory);
+		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<>(sessionFactory);
 		DefaultFileNameGenerator fGenerator = new DefaultFileNameGenerator();
 		fGenerator.setBeanFactory(mock(BeanFactory.class));
 		fGenerator.setExpression("'foo.txt'");
@@ -173,7 +181,7 @@ public void testSftpOutboundChannelAdapterInsideChain() throws Exception {
 	}
 
 	@Test //INT-2275
-	public void testFtpOutboundGatewayInsideChain() throws Exception {
+	public void testFtpOutboundGatewayInsideChain() {
 		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
 				"SftpOutboundInsideChainTests-context.xml", getClass());
 
@@ -204,12 +212,12 @@ public void testMkDir() throws Exception {
 		@SuppressWarnings("unchecked")
 		SessionFactory<LsEntry> sessionFactory = mock(SessionFactory.class);
 		when(sessionFactory.getSession()).thenReturn(session);
-		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<LsEntry>(sessionFactory);
+		FileTransferringMessageHandler<LsEntry> handler = new FileTransferringMessageHandler<>(sessionFactory);
 		handler.setAutoCreateDirectory(true);
 		handler.setRemoteDirectoryExpression(new LiteralExpression("/foo/bar/baz"));
 		handler.setBeanFactory(mock(BeanFactory.class));
 		handler.afterPropertiesSet();
-		final List<String> madeDirs = new ArrayList<String>();
+		final List<String> madeDirs = new ArrayList<>();
 		doAnswer(invocation -> {
 			madeDirs.add(invocation.getArgument(0));
 			return null;
@@ -374,6 +382,38 @@ public void testSharedSessionCachedReset() throws Exception {
 		verify(jschSession2).disconnect();
 	}
 
+	@Test
+	public void testExists() throws SftpException, IOException {
+		ChannelSftp channelSftp = mock(ChannelSftp.class);
+
+		willReturn(mock(SftpATTRS.class))
+				.given(channelSftp)
+				.lstat(eq("exist"));
+
+		willThrow(new SftpException(ChannelSftp.SSH_FX_NO_SUCH_FILE, "Path does not exist."))
+				.given(channelSftp)
+				.lstat(eq("notExist"));
+
+		willThrow(new SftpException(ChannelSftp.SSH_FX_CONNECTION_LOST, "Connection lost."))
+				.given(channelSftp)
+				.lstat(eq("foo"));
+
+		SftpSession sftpSession = new SftpSession(mock(com.jcraft.jsch.Session.class));
+		DirectFieldAccessor fieldAccessor = new DirectFieldAccessor(sftpSession);
+		fieldAccessor.setPropertyValue("channel", channelSftp);
+
+		assertTrue(sftpSession.exists("exist"));
+
+		assertFalse(sftpSession.exists("notExist"));
+
+		try {
+			sftpSession.exists("foo");
+			fail("Expected exception");
+		}
+		catch (UncheckedIOException e) {
+		}
+	}
+
 	private void noopConnect(ChannelSftp channel1) throws JSchException {
 		doAnswer(invocation -> null).when(channel1).connect();
 	}

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/outbound/SftpServerOutboundTests.java

@@ -21,6 +21,7 @@
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
@@ -35,6 +36,7 @@
 import java.io.IOException;
 import java.io.PipedInputStream;
 import java.io.PipedOutputStream;
+import java.io.UncheckedIOException;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executors;
@@ -56,6 +58,7 @@
 import org.springframework.integration.file.remote.session.Session;
 import org.springframework.integration.file.remote.session.SessionFactory;
 import org.springframework.integration.sftp.SftpTestSupport;
+import org.springframework.integration.sftp.session.DefaultSftpSessionFactory;
 import org.springframework.integration.sftp.session.SftpRemoteFileTemplate;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.integration.test.util.TestUtils;
@@ -497,6 +500,29 @@ private void assertLength6(SftpRemoteFileTemplate template) {
 		assertEquals(6, files[0].getAttrs().getSize());
 	}
 
+	@Test
+	public void testSessionExists() throws IOException {
+		DefaultSftpSessionFactory sessionFactory = new DefaultSftpSessionFactory();
+		sessionFactory.setHost("localhost");
+		sessionFactory.setPort(port);
+		sessionFactory.setUser("foo");
+		sessionFactory.setPassword("foo");
+		sessionFactory.setAllowUnknownKeys(true);
+		Session<LsEntry> session = sessionFactory.getSession();
+
+		assertTrue(session.exists("sftpSource"));
+		assertFalse(session.exists("notExist"));
+
+		session.close();
+
+		try {
+			session.exists("any");
+			fail("expected exception");
+		}
+		catch (UncheckedIOException e) {
+		}
+	}
+
 	@SuppressWarnings("unused")
 	private static final class TestMessageSessionCallback
 			implements MessageSessionCallback<LsEntry, Object> {