INT-3310 Fix Syslog Error on Socket Close

https://jira.springsource.org/browse/INT-3310

Previously, the syslog adapter tried to convert the ErrorMessage
that results from a socket error to a syslog packet, resulting
in a stack trace on stderr.

Test for the ErrorMessage and log at DEBUG.

spring-integration-syslog/src/test/java/org/springframework/integration/syslog/inbound/SyslogReceivingChannelAdapterTests.java

@@ -19,8 +19,11 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyString;
 import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 
 import java.net.DatagramPacket;
 import java.net.DatagramSocket;
@@ -31,15 +34,18 @@ import java.util.concurrent.TimeUnit;
 
 import javax.net.SocketFactory;
 
+import org.apache.commons.logging.Log;
 import org.junit.Test;
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 
+import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.integration.channel.QueueChannel;
 import org.springframework.integration.syslog.config.SyslogReceivingChannelAdapterFactoryBean;
 import org.springframework.integration.test.util.SocketUtils;
+import org.springframework.integration.test.util.TestUtils;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.PollableChannel;
 
@@ -95,11 +101,27 @@ public class SyslogReceivingChannelAdapterTests {
 		factory.afterPropertiesSet();
 		factory.start();
 		TcpSyslogReceivingChannelAdapter adapter = (TcpSyslogReceivingChannelAdapter) factory.getObject();
+		Log logger = spy(TestUtils.getPropertyValue(adapter, "logger", Log.class));
+		doReturn(true).when(logger).isDebugEnabled();
+		final CountDownLatch sawLog = new CountDownLatch(1);
+		doAnswer(new Answer<Void>(){
+
+			@Override
+			public Void answer(InvocationOnMock invocation) throws Throwable {
+				if (((String) invocation.getArguments()[0]).contains("Error on syslog socket")) {
+					sawLog.countDown();
+				}
+				invocation.callRealMethod();
+				return null;
+			}
+		}).when(logger).debug(anyString());
+		new DirectFieldAccessor(adapter).setPropertyValue("logger", logger);
 		Thread.sleep(1000);
 		byte[] buf = "<157>JUL 26 22:08:35 WEBERN TESTING[70729]: TEST SYSLOG MESSAGE\n".getBytes("UTF-8");
 		Socket socket = SocketFactory.getDefault().createSocket("localhost", port);
 		socket.getOutputStream().write(buf);
 		socket.close();
+		assertTrue(sawLog.await(10, TimeUnit.SECONDS));
 		Message<?> message = outputChannel.receive(10000);
 		assertNotNull(message);
 		assertEquals("WEBERN", message.getHeaders().get("syslog_HOST"));