Merge changes from topic 'events'

* changes:
  Add a custom JSON deserializer for ChangeEvents
  Add EventTypes class registering all stream event types

Documentation/dev-plugins.txt

@@ -415,6 +415,13 @@ methods in the `ChangeHookRunner` class, passing an instance of
 its own custom event class derived from
 `com.google.gerrit.server.events.Event`.
 
+Plugins which define new Events should register them via the
+`com.google.gerrit.server.events.EventTypes.registerClass()`
+method. This will make the EventType known to the system.
+Deserialzing events with the
+`com.google.gerrit.server.events.EventDeserializer` class requires
+that the event be registered in EventTypes.
+
 [[validation]]
 == Validation Listeners
 

gerrit-server/src/main/java/com/google/gerrit/server/events/CommitReceivedEvent.java

@@ -21,15 +21,19 @@ import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.transport.ReceiveCommand;
 
 public class CommitReceivedEvent extends RefEvent {
-  public final ReceiveCommand command;
-  public final Project project;
-  public final String refName;
-  public final RevCommit commit;
-  public final IdentifiedUser user;
+  public ReceiveCommand command;
+  public Project project;
+  public String refName;
+  public RevCommit commit;
+  public IdentifiedUser user;
+
+  public CommitReceivedEvent() {
+    super("commit-received");
+  }
 
   public CommitReceivedEvent(ReceiveCommand command, Project project,
       String refName, RevCommit commit, IdentifiedUser user) {
-    super("commit-received");
+    this();
     this.command = command;
     this.project = project;
     this.refName = refName;

gerrit-server/src/main/java/com/google/gerrit/server/events/EventDeserializer.java

@@ -0,0 +1,49 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.events;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+
+import java.lang.reflect.Type;
+
+/**
+ * JSON deserializer for {@link Event}s.
+ * <p>
+ * Deserialized objects are of an appropriate subclass based on the value of the
+ * top-level "type" element.
+ */
+public class EventDeserializer implements JsonDeserializer<Event> {
+  @Override
+  public Event deserialize(JsonElement json, Type typeOfT,
+      JsonDeserializationContext context) throws JsonParseException {
+    if (!json.isJsonObject()) {
+      throw new JsonParseException("Not an object");
+    }
+    JsonElement typeJson = json.getAsJsonObject().get("type");
+    if (typeJson == null || !typeJson.isJsonPrimitive()
+        || !typeJson.getAsJsonPrimitive().isString()) {
+      throw new JsonParseException("Type is not a string: " + typeJson);
+    }
+    String type = typeJson.getAsJsonPrimitive().getAsString();
+    Class<?> cls = EventTypes.getClass(type);
+    if (cls == null) {
+      throw new JsonParseException("Unknown event type: " + type);
+    }
+    return context.deserialize(json, cls);
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/events/EventTypes.java

@@ -0,0 +1,64 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.events;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/** Class for registering event types */
+public class EventTypes {
+  private static final Map<String, Class<?>> typesByString = new HashMap<>();
+
+  static {
+    registerClass(new ChangeAbandonedEvent());
+    registerClass(new ChangeMergedEvent());
+    registerClass(new ChangeRestoredEvent());
+    registerClass(new CommentAddedEvent());
+    registerClass(new CommitReceivedEvent());
+    registerClass(new DraftPublishedEvent());
+    registerClass(new HashtagsChangedEvent());
+    registerClass(new MergeFailedEvent());
+    registerClass(new RefUpdatedEvent());
+    registerClass(new RefReceivedEvent());
+    registerClass(new ReviewerAddedEvent());
+    registerClass(new PatchSetCreatedEvent());
+    registerClass(new TopicChangedEvent());
+  }
+
+  /** Register an event.
+   *
+   *  @param event The event to register.
+   *  @throws IllegalArgumentException if the event's type is already
+   *  registered.
+   **/
+  public static void registerClass(Event event) {
+    String type = event.getType();
+    if (typesByString.containsKey(type)) {
+      throw new IllegalArgumentException(
+          "Event type already registered: " + type);
+    }
+    typesByString.put(type, event.getClass());
+  }
+
+  /** Get the class for an event type.
+   *
+   * @param type The type.
+   * @return The event class, or null if no class is registered with the
+   * given type
+   **/
+  public static Class<?> getClass(String type) {
+    return typesByString.get(type);
+  }
+}