HelloAsyncActivityCompletion added

Author: Maxim Fateev

src/main/java/com/uber/cadence/samples/hello/HelloAsyncActivityCompletion.java

@@ -0,0 +1,130 @@
+/*
+ *  Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"). You may not
+ *  use this file except in compliance with the License. A copy of the License is
+ *  located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ *  or in the "license" file accompanying this file. This file 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.uber.cadence.samples.hello;
+
+import com.uber.cadence.activity.Activity;
+import com.uber.cadence.activity.DoNotCompleteOnReturn;
+import com.uber.cadence.client.ActivityCompletionClient;
+import com.uber.cadence.client.WorkflowClient;
+import com.uber.cadence.client.WorkflowOptions;
+import com.uber.cadence.worker.Worker;
+import com.uber.cadence.workflow.ActivityOptions;
+import com.uber.cadence.workflow.Workflow;
+import com.uber.cadence.workflow.WorkflowMethod;
+
+import java.util.concurrent.ForkJoinPool;
+
+import static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
+
+/**
+ * Hello World Cadence workflow that executes a single activity.
+ * Requires a local instance of Cadence server running.
+ */
+public class HelloAsyncActivityCompletion {
+
+    private static final String TASK_LIST = "HelloActivity";
+
+    /**
+     * Workflow interface has to have at least one method annotated with @WorkflowMethod.
+     */
+    public interface GreetingWorkflow {
+        /**
+         * @return greeting string
+         */
+        @WorkflowMethod
+        String getGreeting(String name);
+    }
+
+    /**
+     * Activity interface is just a POJI
+     */
+    public interface GreetingActivities {
+        String composeGreeting(String greeting, String name);
+    }
+
+    /**
+     * GreetingWorkflow implementation that calls GreetingsActivities#printIt.
+     */
+    public static class GreetingWorkflowImpl implements GreetingWorkflow {
+
+        /**
+         * Activity stub implements activity interface and proxies calls to it to Cadence activity invocations.
+         * As activities are reentrant only a single stub can be used for multiple activity invocations.
+         */
+        private final GreetingActivities activities = Workflow.newActivityStub(
+                GreetingActivities.class,
+                new ActivityOptions.Builder().setScheduleToCloseTimeoutSeconds(10).build());
+
+        @Override
+        public String getGreeting(String name) {
+            // This is blocking call that returns only after activity is completed.
+            return activities.composeGreeting("Hello", name);
+        }
+    }
+
+    private static class GreetingActivitiesImpl implements GreetingActivities {
+        WorkflowClient workflowClient = WorkflowClient.newInstance(DOMAIN);
+
+        /**
+         * Demonstrates how implement an activity asynchronously.
+         * When @DoNotCompleteOnReturn is present activity implementation function returning doesn't complete
+         * the activity.
+         */
+        @DoNotCompleteOnReturn
+        @Override
+        public String composeGreeting(String greeting, String name) {
+            // TaskToken is a correlation token used to match activity task with completion
+            byte[] taskToken = Activity.getTaskToken();
+            // In real life this request can be executed anywhere. By external service for example.
+            ForkJoinPool.commonPool().execute(() -> composeGreetingAsync(taskToken, greeting, name));
+            // When @DoNotCompleteOnReturn is specified the return value is ignored.
+            return "ignored";
+        }
+
+        private void composeGreetingAsync(byte[] taskToken, String greeting, String name) {
+            // To complete activity from a different thread or process use ActivityCompletionClient.
+            ActivityCompletionClient completionClient = workflowClient.newActivityCompletionClient();
+            String result = greeting + " " + name + "!";
+            completionClient.complete(taskToken, result);
+        }
+    }
+
+    public static void main(String[] args) {
+        // Start a worker that hosts both workflow and activity implementation
+        Worker worker = new Worker(DOMAIN, TASK_LIST);
+        // Workflows are stateful. So need a type to create instances.
+        worker.registerWorkflowImplementationTypes(GreetingWorkflowImpl.class);
+        // Activities are stateless and thread safe. So a shared instance is used.
+        worker.registerActivitiesImplementations(new GreetingActivitiesImpl());
+        // Start listening to the workflow and activity task lists.
+        worker.start();
+
+        // Start a workflow execution. Usually it is done from another program.
+        WorkflowClient workflowClient = WorkflowClient.newInstance(DOMAIN);
+        // Get a workflow stub using the same task list the worker uses.
+        WorkflowOptions workflowOptions = new WorkflowOptions.Builder()
+                .setTaskList(TASK_LIST)
+                .setExecutionStartToCloseTimeoutSeconds(30)
+                .build();
+        GreetingWorkflow workflow = workflowClient.newWorkflowStub(GreetingWorkflow.class,
+                workflowOptions);
+        // Execute a workflow waiting for it complete.
+        String greeting = workflow.getGreeting("World");
+        System.out.println(greeting);
+        System.exit(0);
+    }
+}