INT-4340: Disable XMPP Roster properly

JIRA: https://jira.spring.io/browse/INT-4340

* Roster is now disabled on login as well
* Fixed tagging and formatting issues
* Checkstyle and documented the changed behaviour as well

Polishing: rely on the `AbstractFactoryBean.getObject()`

**Cherry-pick to 4.3.x**

spring-integration-xmpp/src/test/java/org/springframework/integration/xmpp/config/XmppConnectionFactoryBeanTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -16,10 +16,14 @@
 
 package org.springframework.integration.xmpp.config;
 
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 
 import org.jivesoftware.smack.XMPPConnection;
+import org.jivesoftware.smack.roster.Roster;
+import org.jivesoftware.smack.tcp.XMPPTCPConnection;
 import org.jivesoftware.smack.tcp.XMPPTCPConnectionConfiguration;
 import org.junit.Test;
 
@@ -29,6 +33,7 @@ import org.springframework.context.support.ClassPathXmlApplicationContext;
  * @author Oleg Zhurakousky
  * @author Gunnar Hillert
  * @author Artem Bilan
+ * @author Philipp Etschel
  */
 public class XmppConnectionFactoryBeanTests {
 
@@ -46,4 +51,44 @@ public class XmppConnectionFactoryBeanTests {
 		// the fact that no exception was thrown satisfies this test
 	}
 
+	@Test
+	public void testXmppConnectionFactoryBeanNoRoster() throws Exception {
+		XmppConnectionFactoryBean xmppConnectionFactoryBean =
+				new XmppConnectionFactoryBean() {
+
+					@Override
+					protected XMPPConnection createInstance() throws Exception {
+						return mock(XMPPTCPConnection.class);
+					}
+
+				};
+
+		xmppConnectionFactoryBean.setSubscriptionMode(null);
+		xmppConnectionFactoryBean.afterPropertiesSet();
+		xmppConnectionFactoryBean.start();
+		XMPPConnection connection = xmppConnectionFactoryBean.getObject();
+
+		assertFalse(Roster.getInstanceFor(connection).isRosterLoadedAtLogin());
+	}
+
+	@Test
+	public void testXmppConnectionFactoryBeanWithRoster() throws Exception {
+		XmppConnectionFactoryBean xmppConnectionFactoryBean =
+				new XmppConnectionFactoryBean() {
+
+					@Override
+					protected XMPPConnection createInstance() throws Exception {
+						return mock(XMPPTCPConnection.class);
+					}
+
+				};
+
+		xmppConnectionFactoryBean.setSubscriptionMode(Roster.SubscriptionMode.accept_all);
+		xmppConnectionFactoryBean.afterPropertiesSet();
+		xmppConnectionFactoryBean.start();
+		XMPPConnection connection = xmppConnectionFactoryBean.getObject();
+
+		assertTrue(Roster.getInstanceFor(connection).isRosterLoadedAtLogin());
+	}
+
 }