Pluggable Streamer Prototype in Java

src/main/java/org/eclipse/uprotocol/core/usubscription/v3/USubscription.java

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+package org.eclipse.uprotocol.core.usubscription.v3;
+
+import org.eclipse.uprotocol.v1.UStatus;
+import org.eclipse.uprotocol.core.usubscription.v3.*;
+
+/* The following is the uSubscription API declared as an interface so it could be easily 
+ * used  
+ */
+public interface USubscription {
+
+
+    /**
+     * A consumer (application) calls this API to subscribe to a topic.
+     * What is passed is the SubscriptionRequest message containing the topic, the
+     * subscriber's name, and any Subscription Attributes. This API returns a
+     * SubscriptionResponse message containing the status of the request along with
+     * any event delivery configuration
+     * required to consume the event. Calling this API also registers the subscriber
+     * to received subscription change notifications if ever the subscription state
+     * changes.
+     * @param request the request containing the topic, subscriber name, and subscription attributes
+     * @return the response containing the status of the request and any event delivery configuration
+     */
+    SubscriptionResponse subscribe(SubscriptionRequest request);
+
+
+    // The consumer no longer wishes to subscribe to a topic so it issues an
+    // explicit unsubscribe request.
+    UStatus unsubscribe(UnsubscribeRequest request);
+
+
+    /**
+     * Fetch a list of subscribers that are currently subscribed to a given topic.
+     * @param request the request containing the topic that we want the list of subscribers for
+     * @return the list of subscribers for the given topic
+     */
+    FetchSubscribersResponse fetchSubscribers(FetchSubscribersRequest request);
+
+
+    /**
+     * Reset subscriptions to and from the uSubscription Service.
+     * This API is used between uSubscription services in order to flush and 
+     * reestablish subscriptions between devices. A uSubscription service might 
+     * ned to call this API if its database is flushed or corrupted (ex. factory
+     * reset).
+     * **__NOTE:__** This is a private API only for uSubscription services,
+     * uEs can call Unsubscribe() to flush their own subscriptions.
+     * 
+     * @param request the request containing the reset information
+     * @return the status of the reset request
+     */
+    UStatus reset(ResetRequest request);
+
+
+    /**
+     * Fetch a list of subscriptions for a given subscriber.
+     * @param request the request containing the subscriber
+     * @return the list of subscriptions for the subscriber
+     */
+    FetchSubscriptionsResponse fetchSubscriptions(FetchSubscriptionsRequest request);
+
+
+    /**
+     * Register for subscription change notifications for a given topic
+     * @param request the request containing the topic
+     * @return the status of the request
+     */
+    UStatus registerForNotifications(NotificationsRequest request);
+
+    /**
+     * Unregister for subscription change notifications for a given topic
+     * @param request the request containing the topic
+     * @return the status from unregistering for a subscription change notification
+     */
+    UStatus unregisterForNotifications(NotificationsRequest request);
+}

src/main/java/org/eclipse/uprotocol/streamer/README.adoc

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+# Plugable Streamer
+
+This is a simple example of a plugable streamer that is used to demonstrate how someone would implement the uStreamer using the UTransport interface. 
+
+For more information on the design, please refer to the code and uProtocol specifications.
+
+NOTE: The following is reference example code and not intended to be used to build an actual production uStreamer
+

src/main/java/org/eclipse/uprotocol/streamer/Route.java

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+/*
+ * Copyright (c) 2024 General Motors GTO LLC
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ * 
+ * SPDX-FileType: SOURCE
+ * SPDX-FileCopyrightText: 2024 General Motors GTO LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+ package org.eclipse.uprotocol.streamer;
+
+import org.eclipse.uprotocol.transport.UTransport;
+import org.eclipse.uprotocol.v1.UAuthority;
+
+/**
+ * Route is defined as a combination of UAuthority and UTransport as routes are at the UAuthority level.
+ *
+ */
+public class Route {
+    private UAuthority authority;
+    private UTransport transport;
+
+    /**
+     * Constructor
+     * @param authority 
+     * @param transport
+     */
+    Route(UAuthority authority, UTransport transport) {
+        this.authority = authority;
+        this.transport = transport;
+    }
+
+    /** 
+     * Fetch the authority
+     * @return UAuthority
+     */
+    public UAuthority getAuthority() {
+        return authority;
+    }
+
+    /**
+     * Fetch the transport
+     * @return UTransport
+     */
+    public UTransport getTransport() {
+        return transport;
+    }
+}

src/main/java/org/eclipse/uprotocol/streamer/TransportListener.java

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+/*
+ * Copyright (c) 2024 General Motors GTO LLC
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ * 
+ * SPDX-FileType: SOURCE
+ * SPDX-FileCopyrightText: 2024 General Motors GTO LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.eclipse.uprotocol.streamer;
+
+import org.eclipse.uprotocol.transport.UListener;
+import org.eclipse.uprotocol.v1.UMessage;
+
+
+/**
+ * Transport Listener receives a message that is destine for another transport so 
+ * it simply forwards the message to the output UTransport.
+ */
+class TransportListener implements UListener {
+
+    private Route in;
+    private Route out; 
+
+    @Override
+    public void onReceive(UMessage message) {
+        out.getTransport().send(message);
+    }
+
+    /**
+     * Constructor passing the input and output routes
+     * @param in input Route
+     * @param out output Route
+     */
+    public TransportListener(Route in, Route out) {
+        this.in = in;
+        this.out = out;
+    }
+
+    /**
+     * Fetch the input route
+     * @return input Route
+     */
+    public Route getInputRoute() {
+        return in;
+    }
+
+    /** 
+     * Fetch the output route
+     * @return output Route
+     */
+    public Route getOutputRoute() {
+        return out;
+    }
+
+}