Relay project events as raw JSON instead of deserializing them

Delivering a change bundle failed at the gateway with a Jackson error:
the sequenced event and the history-query response typed their inner
events against this service's own event model, and the event-history
service's serialization of a hierarchy-changed event does not construct
under it. The gateway never acts on the inner events — it only relays
them to browsers — so the event list and the sequenced bundle now carry
them as raw JSON. What reaches the client is byte-for-byte what the
producer serialized, and the gateway stops breaking whenever its copy of
the event model drifts from a producer's.

Found running the end-to-end suite against the epic stack: viewers
opened streams fine but never received a single event.

Part of protegeproject/webprotege-gwt-ui#304
(epic protegeproject/webprotege-gwt-ui#303).

Author: johardi

src/main/java/edu/stanford/protege/webprotege/gateway/websocket/dto/EventList.java

@@ -1,9 +1,14 @@
 package edu.stanford.protege.webprotege.gateway.websocket.dto;
 
-import edu.stanford.protege.webprotege.common.Event;
+import com.fasterxml.jackson.databind.JsonNode;
 import edu.stanford.protege.webprotege.event.EventTag;
 
-import java.util.List;
-
-public record EventList <E extends Event> (EventTag startTag, List<E> events, EventTag endTag){
+/**
+ * The window of events the client receives. The gateway only relays the events — it never acts on
+ * their contents — so they are carried as raw JSON rather than typed objects: the producers (the
+ * backend and the event-history service) and the browser client agree on the event payloads, and
+ * forcing them through this service's own event model just makes delivery fail whenever the
+ * gateway's model drifts from the producer's serialization.
+ */
+public record EventList(EventTag startTag, JsonNode events, EventTag endTag) {
 }

src/main/java/edu/stanford/protege/webprotege/gateway/websocket/dto/SequencedPackagedProjectChangeEvent.java

@@ -1,12 +1,12 @@
 package edu.stanford.protege.webprotege.gateway.websocket.dto;
 
 import com.fasterxml.jackson.annotation.JsonTypeName;
+import com.fasterxml.jackson.databind.JsonNode;
 import edu.stanford.protege.webprotege.common.EventId;
 import edu.stanford.protege.webprotege.common.ProjectEvent;
 import edu.stanford.protege.webprotege.common.ProjectId;
 
 import javax.annotation.Nonnull;
-import java.util.List;
 
 /**
  * A {@link PackagedProjectChangeEvent} enriched with the per-project sequence ordinal assigned to the
@@ -16,10 +16,12 @@
  * <p>
  * This is a gateway-local mirror of the producer's event; the field names ({@code projectId},
  * {@code eventId}, {@code sequenceNumber}, {@code projectEvents}) are the wire contract and must
- * match the producer exactly.
+ * match the producer exactly. The inner events stay raw JSON on purpose: the gateway only relays
+ * them, and deserializing them into this service's own event model breaks delivery whenever that
+ * model drifts from the producer's serialization.
  */
 @JsonTypeName(SequencedPackagedProjectChangeEvent.CHANNEL)
-public record SequencedPackagedProjectChangeEvent(ProjectId projectId, EventId eventId, int sequenceNumber, List<ProjectEvent> projectEvents) implements ProjectEvent {
+public record SequencedPackagedProjectChangeEvent(ProjectId projectId, EventId eventId, int sequenceNumber, JsonNode projectEvents) implements ProjectEvent {
 
     public final static String CHANNEL = "webprotege.events.projects.SequencedPackagedProjectChange";
 

src/test/java/edu/stanford/protege/webprotege/gateway/sse/HistoryReplaySseCatchUpServiceTest.java

@@ -1,6 +1,7 @@
 package edu.stanford.protege.webprotege.gateway.sse;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.google.common.util.concurrent.MoreExecutors;
 import edu.stanford.protege.webprotege.common.ProjectId;
 import edu.stanford.protege.webprotege.common.UserId;
@@ -122,13 +123,13 @@ void failedHistoryQueryKeepsStreamLiveInsteadOfKillingIt() throws IOException {
 
     private static ProjectEventsQueryResponse liveResponse() {
         ProjectEventsQueryResponse response = new ProjectEventsQueryResponse();
-        response.events = new EventList<>(EventTag.getFirst(), List.of(), EventTag.get(1));
+        response.events = new EventList(EventTag.getFirst(), JsonNodeFactory.instance.arrayNode(), EventTag.get(1));
         return response;
     }
 
     private static ProjectEventsQueryResponse historyResponse(int startTag, int endTag) {
         ProjectEventsQueryResponse response = new ProjectEventsQueryResponse();
-        response.events = new EventList<>(EventTag.get(startTag), List.of(), EventTag.get(endTag));
+        response.events = new EventList(EventTag.get(startTag), JsonNodeFactory.instance.arrayNode(), EventTag.get(endTag));
         return response;
     }
 

src/test/java/edu/stanford/protege/webprotege/gateway/sse/SseStreamRegistryTest.java

@@ -1,5 +1,6 @@
 package edu.stanford.protege.webprotege.gateway.sse;
 
+import com.fasterxml.jackson.databind.node.JsonNodeFactory;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import edu.stanford.protege.webprotege.common.ProjectId;
 import edu.stanford.protege.webprotege.common.UserId;
@@ -176,7 +177,7 @@ void completeCatchUpWithoutReplayFlushesBufferedThenResumesLiveDelivery() throws
 
     private static ProjectEventsQueryResponse response() {
         ProjectEventsQueryResponse response = new ProjectEventsQueryResponse();
-        response.events = new EventList<>(EventTag.getFirst(), List.of(), EventTag.get(1));
+        response.events = new EventList(EventTag.getFirst(), JsonNodeFactory.instance.arrayNode(), EventTag.get(1));
         return response;
     }
 

src/test/java/edu/stanford/protege/webprotege/gateway/websocket/ProjectChangedEmitterHandlerTest.java

@@ -66,7 +66,8 @@ void setUp() {
                 projectId,
                 new OWLClassImpl(IRI.create("http://www.example.org/R9UuCy8Vzvft2f4fc67VwGs")),
                 new ArrayList<>());
-        sequencedEvent = new SequencedPackagedProjectChangeEvent(projectId, eventId, SEQUENCE_NUMBER, List.of(entityTagsChangedEvent));
+        sequencedEvent = new SequencedPackagedProjectChangeEvent(projectId, eventId, SEQUENCE_NUMBER,
+                                                                  objectMapper.valueToTree(List.of(entityTagsChangedEvent)));
     }
 
     @Test
@@ -133,7 +134,7 @@ void GIVEN_sequencedEvent_WHEN_handleEvent_THEN_publishedToSseRegistryWithSequen
         ArgumentCaptor<ProjectEventsQueryResponse> sseCaptor = ArgumentCaptor.forClass(ProjectEventsQueryResponse.class);
         verify(sseStreamRegistry).publish(eq(projectId), eq((long) SEQUENCE_NUMBER), sseCaptor.capture());
 
-        EventList<?> events = sseCaptor.getValue().events;
+        EventList events = sseCaptor.getValue().events;
         assertEquals(SEQUENCE_NUMBER - 1, events.startTag().getOrdinal());
         assertEquals(SEQUENCE_NUMBER, events.endTag().getOrdinal());
         assertEquals(sequencedEvent.projectEvents(), events.events());