Add sample for local activity

Author: longquanzheng

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

@@ -0,0 +1,94 @@
+/*
+ *  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 static com.uber.cadence.samples.common.SampleConstants.DOMAIN;
+
+import com.uber.cadence.activity.ActivityMethod;
+import com.uber.cadence.client.WorkflowClient;
+import com.uber.cadence.worker.Worker;
+import com.uber.cadence.workflow.Workflow;
+import com.uber.cadence.workflow.WorkflowMethod;
+
+/**
+ * Hello World Cadence workflow that executes a single activity. Requires a local instance the
+ * Cadence service to be running.
+ */
+public class HelloLocalActivity {
+
+  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(executionStartToCloseTimeoutSeconds = 10, taskList = TASK_LIST)
+    String getGreeting(String name);
+  }
+
+  /** Activity interface is just a POJI. */
+  public interface GreetingActivities {
+    @ActivityMethod(scheduleToCloseTimeoutSeconds = 2)
+    String composeGreeting(String greeting, String name);
+  }
+
+  /** GreetingWorkflow implementation that calls GreetingsActivities#composeGreeting. */
+  public static class GreetingWorkflowImpl implements GreetingWorkflow {
+
+    /**
+     * Activity stub implements activity interface and proxies calls to it to Cadence activity
+     * invocations. Because activities are reentrant, only a single stub can be used for multiple
+     * activity invocations.
+     */
+    private final GreetingActivities activities =
+        Workflow.newLocalActivityStub(GreetingActivities.class);
+
+    @Override
+    public String getGreeting(String name) {
+      // This is a blocking call that returns only after the activity has completed.
+      return activities.composeGreeting("Hello", name);
+    }
+  }
+
+  static class GreetingActivitiesImpl implements GreetingActivities {
+    @Override
+    public String composeGreeting(String greeting, String name) {
+      return greeting + " " + name + "!";
+    }
+  }
+
+  public static void main(String[] args) {
+    // Start a worker that hosts both workflow and activity implementations.
+    Worker.Factory factory = new Worker.Factory(DOMAIN);
+    Worker worker = factory.newWorker(TASK_LIST);
+    // Workflows are stateful. So you 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.
+    factory.start();
+
+    // Start a workflow execution. Usually this is done from another program.
+    WorkflowClient workflowClient = WorkflowClient.newInstance(DOMAIN);
+    // Get a workflow stub using the same task list the worker uses.
+    GreetingWorkflow workflow = workflowClient.newWorkflowStub(GreetingWorkflow.class);
+    // Execute a workflow waiting for it to complete.
+    String greeting = workflow.getGreeting("World");
+    System.out.println(greeting);
+    System.exit(0);
+  }
+}