Compatibility for independent bus clients (#76)

independent bus clients may not have all events implemented or the location of the event classes could be in a different package.
This PR fixes issues in such an environment (e.g. Microservices). Therefore the event type in the AckRemoteApplicationEvent will be set via a special setter, so the availability of the type can be checked.
In addition the UnknownRemoteApplicationEvent is fixed to not cause a NullPointerException when raised.

Fixes #74

spring-cloud-bus/src/main/java/org/springframework/cloud/bus/event/AckRemoteApplicationEvent.java

@@ -17,6 +17,8 @@
 
 package org.springframework.cloud.bus.event;
 
+import com.fasterxml.jackson.annotation.JsonProperty;
+
 /**
  * An event that signals an ack of a specific {@link RemoteApplicationEvent}. These events
  * can be monitored by any applications that want to audit the responses to bus events.
@@ -31,7 +33,7 @@ public class AckRemoteApplicationEvent extends RemoteApplicationEvent {
 
 	private final String ackId;
 	private final String ackDestinationService;
-	private final Class<? extends RemoteApplicationEvent> event;
+	private Class<? extends RemoteApplicationEvent> event;
 
 	@SuppressWarnings("unused")
 	private AckRemoteApplicationEvent() {
@@ -62,6 +64,21 @@ public class AckRemoteApplicationEvent extends RemoteApplicationEvent {
 		return event;
 	}
 
+	/**
+	 * Used by Jackson to set the remote class name of the event implementation. If the implementing class is unknown to
+	 * this app, set the event to {@link UnknownRemoteApplicationEvent}.
+	 *
+	 * @param eventName  the fq class name of the event implementation, not null
+	 */
+	@JsonProperty("event")
+	public void setEventName(String eventName) {
+		try {
+			event = (Class<? extends RemoteApplicationEvent>) Class.forName(eventName);
+		} catch (ClassNotFoundException e) {
+			event = UnknownRemoteApplicationEvent.class;
+		}
+	}
+
 	@Override
 	public int hashCode() {
 		final int prime = 31;

spring-cloud-bus/src/main/java/org/springframework/cloud/bus/event/UnknownRemoteApplicationEvent.java

@@ -34,7 +34,8 @@ public class UnknownRemoteApplicationEvent extends RemoteApplicationEvent {
 	}
 
 	public UnknownRemoteApplicationEvent(Object source, String typeInfo, byte[] payload) {
-		super(source, null, null);
+		// Initialize originService with an empty String, to avoid NullPointer in AntPathMatcher.
+		super(source, "", null);
 		this.typeInfo = typeInfo;
 		this.payload = payload;
 	}

spring-cloud-bus/src/test/java/org/springframework/cloud/bus/BusAutoConfigurationTests.java

@@ -35,6 +35,7 @@ import org.springframework.boot.autoconfigure.PropertyPlaceholderAutoConfigurati
 import org.springframework.cloud.bus.event.AckRemoteApplicationEvent;
 import org.springframework.cloud.bus.event.RefreshRemoteApplicationEvent;
 import org.springframework.cloud.bus.event.SentApplicationEvent;
+import org.springframework.cloud.bus.event.UnknownRemoteApplicationEvent;
 import org.springframework.cloud.stream.annotation.Output;
 import org.springframework.cloud.stream.test.binder.TestSupportBinderAutoConfiguration;
 import org.springframework.context.ConfigurableApplicationContext;
@@ -206,6 +207,19 @@ public class BusAutoConfigurationTests {
 				this.context.getBean(InboundMessageHandlerConfiguration.class).refresh);
 	}
 
+	/**
+	 * see https://github.com/spring-cloud/spring-cloud-bus/issues/74
+	 */
+	@Test
+	public void inboundNotFromSelfUnknown() {
+		this.context = SpringApplication.run(InboundMessageHandlerConfiguration.class);
+		this.context.setId("bar");
+		this.context.getBean(SpringCloudBusClient.INPUT, MessageChannel.class)
+				.send(new GenericMessage<>(
+						new UnknownRemoteApplicationEvent(this, "UnknownEvent", "yada".getBytes())));
+		// No Exception expected
+	}
+
 	@Configuration
 	@Import({ MessageConsumer.class, BusAutoConfiguration.class,
 			TestSupportBinderAutoConfiguration.class,

spring-cloud-bus/src/test/java/org/springframework/cloud/bus/jackson/SubtypeModuleTests.java

@@ -21,6 +21,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
+import org.springframework.cloud.bus.event.AckRemoteApplicationEvent;
 import org.springframework.cloud.bus.event.RemoteApplicationEvent;
 import org.springframework.cloud.bus.event.UnknownRemoteApplicationEvent;
 import org.springframework.cloud.bus.event.test.TestRemoteApplicationEvent;
@@ -92,6 +93,36 @@ public class SubtypeModuleTests {
 		assertTrue("event is wrong type", event instanceof TypedRemoteApplicationEvent);
 	}
 
+	/**
+	 * see https://github.com/spring-cloud/spring-cloud-bus/issues/74
+	 */
+	@Test
+	public void testDeserializeAckRemoteApplicationEventWithKnownType() throws Exception {
+		BusJacksonMessageConverter converter = new BusJacksonAutoConfiguration().busJsonConverter();
+		converter.afterPropertiesSet();
+		Object event = converter.fromMessage(MessageBuilder.withPayload(
+				"{\"type\":\"AckRemoteApplicationEvent\", \"event\":\"org.springframework.cloud.bus.event.test.TestRemoteApplicationEvent\"}")
+				.build(), RemoteApplicationEvent.class);
+		assertTrue("event is no ack", event instanceof AckRemoteApplicationEvent);
+		AckRemoteApplicationEvent ackEvent = AckRemoteApplicationEvent.class.cast(event);
+		assertEquals("inner ack event has wrong type", TestRemoteApplicationEvent.class, ackEvent.getEvent());
+	}
+
+	/**
+	 * see https://github.com/spring-cloud/spring-cloud-bus/issues/74
+	 */
+	@Test
+	public void testDeserializeAckRemoteApplicationEventWithUnknownType() throws Exception {
+		BusJacksonMessageConverter converter = new BusJacksonAutoConfiguration().busJsonConverter();
+		converter.afterPropertiesSet();
+		Object event = converter.fromMessage(MessageBuilder.withPayload(
+				"{\"type\":\"AckRemoteApplicationEvent\", \"event\":\"foo.bar.TestRemoteApplicationEvent\"}").build(),
+				RemoteApplicationEvent.class);
+		assertTrue("event is no ack", event instanceof AckRemoteApplicationEvent);
+		AckRemoteApplicationEvent ackEvent = AckRemoteApplicationEvent.class.cast(event);
+		assertEquals("inner ack event has wrong type", UnknownRemoteApplicationEvent.class, ackEvent.getEvent());
+	}
+
 	@SuppressWarnings("serial")
 	@JsonTypeName("my")
 	public static class MyRemoteApplicationEvent extends RemoteApplicationEvent {