GH-3249: Fix RemoteFileTemplate dead lock in send

Fixes: #3249

When the `CachingSessionFactory` is configured with small enough pool
and it is very likely that dead lock may happen when `RemoteFileTemplate.send()`
is used.
The problem happens when we reach the `RemoteFileTemplate.exists()` call
which is done from the internal method called from already pulled from cache
`Session`

* Fix `RemoteFileTemplate` to use a `session.exists()` instead on the provided
into the method `Session`
* Demonstrate the problem in the `SftpRemoteFileTemplateTests.testNoDeadLockOnSend()`

**Cherry-pick to 5.2.x, 5.1.x & 4.3.x**

Fix RemoteFileOutboundGWTests for the proper mock

Author: artembilan

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

@@ -386,7 +386,7 @@ public void rename(final String fromPath, final String toPath) {
 	public boolean get(Message<?> message, InputStreamCallback callback) {
 		Assert.notNull(this.fileNameProcessor, "A 'fileNameExpression' is needed to use get");
 		String remotePath = this.fileNameProcessor.processMessage(message);
-		return this.get(remotePath, callback);
+		return get(remotePath, callback);
 	}
 
 	@Override
@@ -559,7 +559,7 @@ else if (FileExistsMode.APPEND.equals(mode)) {
 				session.append(stream, tempFilePath);
 			}
 			else {
-				if (exists(remoteFilePath)) {
+				if (session.exists(remoteFilePath)) {
 					if (FileExistsMode.FAIL.equals(mode)) {
 						throw new MessagingException(
 								"The destination file already exists at '" + remoteFilePath + "'.");

spring-integration-file/src/test/java/org/springframework/integration/file/remote/gateway/RemoteFileOutboundGatewayTests.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.
@@ -30,6 +30,7 @@
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.BDDMockito.willReturn;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
@@ -832,14 +833,10 @@ public void testPutExists() throws Exception {
 		SessionFactory<TestLsEntry> sessionFactory = mock(SessionFactory.class);
 		@SuppressWarnings("unchecked")
 		Session<TestLsEntry> session = mock(Session.class);
-		RemoteFileTemplate<TestLsEntry> template = new RemoteFileTemplate<TestLsEntry>(sessionFactory) {
-
-			@Override
-			public boolean exists(String path) {
-				return true;
-			}
-
-		};
+		willReturn(Boolean.TRUE)
+				.given(session)
+				.exists(anyString());
+		RemoteFileTemplate<TestLsEntry> template = new RemoteFileTemplate<>(sessionFactory);
 		template.setRemoteDirectoryExpression(new LiteralExpression("foo/"));
 		template.setBeanFactory(mock(BeanFactory.class));
 		template.afterPropertiesSet();
@@ -967,6 +964,7 @@ public void testMputRecursive() throws Exception {
 	}
 
 	@Test
+	@SuppressWarnings("unchecked")
 	public void testMputCollection() throws Exception {
 		@SuppressWarnings("unchecked")
 		SessionFactory<TestLsEntry> sessionFactory = mock(SessionFactory.class);

spring-integration-sftp/src/test/java/org/springframework/integration/sftp/session/SftpRemoteFileTemplateTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 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.
@@ -16,11 +16,15 @@
 
 package org.springframework.integration.sftp.session;
 
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.mockito.Mockito.mock;
 
 import java.util.Arrays;
 import java.util.List;
@@ -29,6 +33,7 @@
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
+import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -38,11 +43,13 @@
 import org.springframework.integration.file.remote.SessionCallbackWithoutResult;
 import org.springframework.integration.file.remote.session.CachingSessionFactory;
 import org.springframework.integration.file.remote.session.SessionFactory;
+import org.springframework.integration.file.support.FileExistsMode;
 import org.springframework.integration.sftp.SftpTestSupport;
+import org.springframework.messaging.MessageDeliveryException;
+import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.support.GenericMessage;
 import org.springframework.test.annotation.DirtiesContext;
-import org.springframework.test.context.ContextConfiguration;
-import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.junit4.SpringRunner;
 
 import com.jcraft.jsch.ChannelSftp;
 import com.jcraft.jsch.ChannelSftp.LsEntry;
@@ -51,11 +58,12 @@
 
 /**
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 4.1
  *
  */
-@ContextConfiguration
-@RunWith(SpringJUnit4ClassRunner.class)
+@RunWith(SpringRunner.class)
 @DirtiesContext
 public class SftpRemoteFileTemplateTests extends SftpTestSupport {
 
@@ -67,9 +75,13 @@ public void testINT3412AppendStatRmdir() {
 		SftpRemoteFileTemplate template = new SftpRemoteFileTemplate(sessionFactory);
 		DefaultFileNameGenerator fileNameGenerator = new DefaultFileNameGenerator();
 		fileNameGenerator.setExpression("'foobar.txt'");
+		fileNameGenerator.setBeanFactory(mock(BeanFactory.class));
 		template.setFileNameGenerator(fileNameGenerator);
 		template.setRemoteDirectoryExpression(new LiteralExpression("foo/"));
 		template.setUseTemporaryFileName(false);
+		template.setBeanFactory(mock(BeanFactory.class));
+		template.afterPropertiesSet();
+
 		template.execute(session -> {
 			session.mkdir("foo/");
 			return session.mkdir("foo/bar/");
@@ -101,6 +113,32 @@ public void testINT3412AppendStatRmdir() {
 		assertFalse(template.exists("foo"));
 	}
 
+	@Test
+	public void testNoDeadLockOnSend() {
+		CachingSessionFactory<LsEntry> cachingSessionFactory = new CachingSessionFactory<>(sessionFactory(), 1);
+		SftpRemoteFileTemplate template = new SftpRemoteFileTemplate(cachingSessionFactory);
+		template.setRemoteDirectoryExpression(new LiteralExpression(""));
+		template.setBeanFactory(mock(BeanFactory.class));
+		template.setUseTemporaryFileName(false);
+		DefaultFileNameGenerator fileNameGenerator = new DefaultFileNameGenerator();
+		fileNameGenerator.setExpression("'test.file'");
+		fileNameGenerator.setBeanFactory(mock(BeanFactory.class));
+		template.setFileNameGenerator(fileNameGenerator);
+		template.afterPropertiesSet();
+
+		template.send(new GenericMessage<>(""));
+
+		try {
+			template.send(new GenericMessage<>(""), FileExistsMode.FAIL);
+			fail("Expected exception");
+		}
+		catch (MessageDeliveryException e) {
+			assertThat(e.getCause(), instanceOf(MessagingException.class));
+			assertThat(e.getMessage(), containsString("he destination file already exists at 'test.file'."));
+		}
+		cachingSessionFactory.destroy();
+	}
+
 	@Configuration
 	public static class Config {