1 files changed, 98 insertions, 0 deletions
diff --git a/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/MessageTypeDispatcher.java b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/MessageTypeDispatcher.java
new file mode 100644
index 00000000..195a7eec
--- /dev/null
+++ b/policy-endpoints/src/main/java/org/onap/policy/common/endpoints/listeners/MessageTypeDispatcher.java
@@ -0,0 +1,98 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.endpoints.listeners;
+
+import java.util.concurrent.ConcurrentHashMap;
+import org.onap.policy.common.endpoints.event.comm.Topic.CommInfrastructure;
+import org.onap.policy.common.utils.coder.StandardCoderObject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Dispatches standard objects to listeners, based on the message type extracted from the
+ * message. Only one listener may be registered for a given type.
+ */
+public class MessageTypeDispatcher extends JsonListener {
+    private static final Logger logger = LoggerFactory.getLogger(MessageTypeDispatcher.class);
+
+    /**
+     * Name of the message field, which may be hierarchical.
+     */
+    private final String[] messageFieldNames;
+
+    /**
+     * Name of the message field, joined with "." - for logging.
+     */
+    private final String fullMessageFieldName;
+
+    /**
+     * Maps a message type to its listener.
+     */
+    private final ConcurrentHashMap<String, ScoListener<?>> type2listener = new ConcurrentHashMap<>();
+
+    /**
+     * Constructs the object.
+     *
+     * @param messageFieldNames name of the message field, which may be hierarchical
+     */
+    public MessageTypeDispatcher(String... messageFieldNames) {
+        this.messageFieldNames = messageFieldNames;
+        this.fullMessageFieldName = String.join(".", messageFieldNames);
+    }
+
+    /**
+     * Registers a listener for a certain type of message.
+     *
+     * @param type type of message of interest to the listener
+     * @param listener listener to register
+     */
+    public <T> void register(String type, ScoListener<T> listener) {
+        type2listener.put(type, listener);
+    }
+
+    /**
+     * Unregisters the listener associated with the specified message type.
+     *
+     * @param type type of message whose listener is to be unregistered
+     */
+    public void unregister(String type) {
+        type2listener.remove(type);
+    }
+
+    @Override
+    public void onTopicEvent(CommInfrastructure infra, String topic, StandardCoderObject sco) {
+        // extract the message type
+        final String type = sco.getString(messageFieldNames);
+        if (type == null) {
+            logger.warn("unable to extract {}: {}", fullMessageFieldName, sco);
+            return;
+        }
+
+        // dispatch the message
+        ScoListener<?> listener = type2listener.get(type);
+        if (listener == null) {
+            logger.info("discarding event of type {}", type);
+            return;
+        }
+
+        listener.onTopicEvent(infra, topic, sco);
+    }
+}