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* Bi-di subscription. Add bidi subscription to validate workflow. Signed-off-by: Artur Souza <[email protected]> * Make bi-di subscriber to use Mono Signed-off-by: Artur Souza <[email protected]> --------- Signed-off-by: Artur Souza <[email protected]>
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examples/src/main/java/io/dapr/examples/pubsub/stream/README.md
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| # Dapr Streaming Subscription Sample | ||
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| In this sample, we'll create a publisher and a subscriber java applications using Dapr, based on the publish-subscribe pattern. The publisher will generate messages of a specific topic, while a subscriber will listen for messages of a specific topic via a bi-directional stream. All is abstracted by the SDK. See the [Dapr Pub-Sub docs](https://docs.dapr.io/developing-applications/building-blocks/pubsub/) to understand when this pattern might be a good choice for your software architecture. | ||
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| Visit [this](https://docs.dapr.io/developing-applications/building-blocks/pubsub/pubsub-overview/) link for more information about Dapr and Pub-Sub. | ||
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| ## Pub-Sub Sample using the Java-SDK | ||
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| This sample shows how the subscription to events no longer requires the application to listen to an HTTP or gRPC port. This example uses Redis Streams (enabled in Redis versions => 5). | ||
| ## Pre-requisites | ||
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| * [Dapr CLI](https://docs.dapr.io/getting-started/install-dapr-cli/). | ||
| * Java JDK 11 (or greater): | ||
| * [Microsoft JDK 11](https://docs.microsoft.com/en-us/java/openjdk/download#openjdk-11) | ||
| * [Oracle JDK 11](https://www.oracle.com/technetwork/java/javase/downloads/index.html#JDK11) | ||
| * [OpenJDK 11](https://jdk.java.net/11/) | ||
| * [Apache Maven](https://maven.apache.org/install.html) version 3.x. | ||
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| ### Checking out the code | ||
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| Clone this repository: | ||
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| ```sh | ||
| git clone https://github.com/dapr/java-sdk.git | ||
| cd java-sdk | ||
| ``` | ||
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| Then build the Maven project: | ||
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| ```sh | ||
| # make sure you are in the `java-sdk` directory. | ||
| mvn install | ||
| ``` | ||
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| Then get into the examples directory: | ||
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| ```sh | ||
| cd examples | ||
| ``` | ||
| ### Initialize Dapr | ||
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| Run `dapr init` to initialize Dapr in Self-Hosted Mode if it's not already initialized. | ||
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| ### Running the subscriber | ||
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| The subscriber uses the `DaprPreviewClient` interface to use a new feature where events are subscribed via a streaming and processed via a callback interface. | ||
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| The publisher is a simple Java application with a main method that uses the Dapr gRPC Client to publish 10 messages to a specific topic. | ||
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| In the `Subscriber.java` file, you will find the `Subscriber` class, containing the main method. The main method declares a `DaprPreviewClient` using the `DaprClientBuilder` class. When invoking `subscribeToEvents`, the subscriber provides an implementation of the `SubscriptionListener` interface, receiving a `Subscription` object. The `Subscription` object implements the `Closeable` interface and the `close()` method must be used to stop the subscription. | ||
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| ```java | ||
| public class Subscriber { | ||
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| // ... | ||
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| public static void main(String[] args) throws Exception { | ||
| String topicName = getTopicName(args); | ||
| try (var client = new DaprClientBuilder().buildPreviewClient()) { | ||
| var subscription = client.subscribeToEvents( | ||
| PUBSUB_NAME, | ||
| topicName, | ||
| new SubscriptionListener<>() { | ||
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| @Override | ||
| public Mono<Status> onEvent(CloudEvent<String> event) { | ||
| System.out.println("Subscriber got: " + event.getData()); | ||
| return Mono.just(Status.SUCCESS); | ||
| } | ||
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| @Override | ||
| public void onError(RuntimeException exception) { | ||
| System.out.println("Subscriber got exception: " + exception.getMessage()); | ||
| } | ||
| }, | ||
| TypeRef.STRING); | ||
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| subscription.awaitTermination(); | ||
| } | ||
| } | ||
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| // ... | ||
| } | ||
| ``` | ||
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| Execute the following command to run the Subscriber example: | ||
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| <!-- STEP | ||
| name: Run Subscriber | ||
| expected_stdout_lines: | ||
| - '== APP == Subscriber got: This is message #0' | ||
| - '== APP == Subscriber got: This is message #1' | ||
| background: true | ||
| sleep: 30 | ||
| --> | ||
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| ```bash | ||
| dapr run --resources-path ./components/pubsub --app-id subscriber -- java -jar target/dapr-java-sdk-examples-exec.jar io.dapr.examples.pubsub.stream.Subscriber | ||
| ``` | ||
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| <!-- END_STEP --> | ||
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| Once the subscriber is running, run the publisher in a new terminal to see the events in the subscriber's side: | ||
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| <!-- STEP | ||
| name: Run Publisher | ||
| expected_stdout_lines: | ||
| - '== APP == Published message: This is message #0' | ||
| - '== APP == Published message: This is message #1' | ||
| background: true | ||
| sleep: 15 | ||
| --> | ||
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| ```bash | ||
| dapr run --resources-path ./components/pubsub --app-id publisher -- java -jar target/dapr-java-sdk-examples-exec.jar io.dapr.examples.pubsub.Publisher | ||
| ``` | ||
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| <!-- END_STEP --> | ||
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examples/src/main/java/io/dapr/examples/pubsub/stream/Subscriber.java
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| /* | ||
| * Copyright 2021 The Dapr Authors | ||
| * 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. | ||
| */ | ||
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| package io.dapr.examples.pubsub.stream; | ||
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| import io.dapr.client.DaprClientBuilder; | ||
| import io.dapr.client.SubscriptionListener; | ||
| import io.dapr.client.domain.CloudEvent; | ||
| import io.dapr.utils.TypeRef; | ||
| import reactor.core.publisher.Mono; | ||
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| /** | ||
| * Subscriber using bi-directional gRPC streaming, which does not require an app port. | ||
| * 1. Build and install jars: | ||
| * mvn clean install | ||
| * 2. cd [repo root]/examples | ||
| * 3. Run the subscriber: | ||
| * dapr run --resources-path ./components/pubsub --app-id subscriber -- \ | ||
| * java -jar target/dapr-java-sdk-examples-exec.jar io.dapr.examples.pubsub.stream.Subscriber | ||
| */ | ||
| public class Subscriber { | ||
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| //The title of the topic to be used for publishing | ||
| private static final String DEFAULT_TOPIC_NAME = "testingtopic"; | ||
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| //The name of the pubsub | ||
| private static final String PUBSUB_NAME = "messagebus"; | ||
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| /** | ||
| * This is the entry point for this example app, which subscribes to a topic. | ||
| * @param args Used to optionally pass a topic name. | ||
| * @throws Exception An Exception on startup. | ||
| */ | ||
| public static void main(String[] args) throws Exception { | ||
| String topicName = getTopicName(args); | ||
| try (var client = new DaprClientBuilder().buildPreviewClient()) { | ||
| var subscription = client.subscribeToEvents( | ||
| PUBSUB_NAME, | ||
| topicName, | ||
| new SubscriptionListener<>() { | ||
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| @Override | ||
| public Mono<Status> onEvent(CloudEvent<String> event) { | ||
| System.out.println("Subscriber got: " + event.getData()); | ||
| return Mono.just(Status.SUCCESS); | ||
| } | ||
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| @Override | ||
| public void onError(RuntimeException exception) { | ||
| System.out.println("Subscriber got exception: " + exception.getMessage()); | ||
| } | ||
| }, | ||
| TypeRef.STRING); | ||
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| subscription.awaitTermination(); | ||
| } | ||
| } | ||
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| /** | ||
| * If a topic is specified in args, use that. | ||
| * Else, fallback to the default topic. | ||
| * @param args program arguments | ||
| * @return name of the topic to publish messages to. | ||
| */ | ||
| private static String getTopicName(String[] args) { | ||
| if (args.length >= 1) { | ||
| return args[0]; | ||
| } | ||
| return DEFAULT_TOPIC_NAME; | ||
| } | ||
| } |
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