Creating an Activity State Machine Using Step Functions

In the Step Functions console, in the navigation pane on the left, choose Activities.

Choose Create activity.

Enter an Activity Name, for example, get-greeting, and then choose Create Activity.

When your activity task is created, make a note of its ARN, as shown in the following example.

arn:aws-cn:states:us-east-1:123456789012:activity:get-greeting

In the Step Functions console, in the navigation pane on the left, choose State machines.

On the State machines page, choose Create state machine, and then choose Author with code snippets. For Type, choose Standard, and then enter a name for your state machine (for example, ActivityStateMachine).

Under State machine definition, enter the following code, and include the ARN of the activity task that you created earlier in the Resource field, as shown in the following example.

{
  "Comment": "An example using a Task state.",
  "StartAt": "getGreeting",
  "Version": "1.0",
  "TimeoutSeconds": 300,
  "States":
  {
    "getGreeting": {
      "Type": "Task",
      "Resource": "arn:aws-cn:states:us-east-1:123456789012:activity:get-greeting",
      "End": true
    }
  }
}

This is a description of your state machine using the Amazon States Language. It defines a single Task state named getGreeting. For more information, see State Machine Structure.

Use the graph in the Visual Workflow pane to check that your Amazon States Language code describes your state machine correctly.

If you don't see the graph, choose in the Visual Workflow pane.

Choose Next.

Create or enter an IAM role:

Choose Create state machine.

Create a file named GreeterActivities.java.

Add the following code to it.

import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.EnvironmentVariableCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.stepfunctions.AWSStepFunctions;
import com.amazonaws.services.stepfunctions.AWSStepFunctionsClientBuilder;
import com.amazonaws.services.stepfunctions.model.GetActivityTaskRequest;
import com.amazonaws.services.stepfunctions.model.GetActivityTaskResult;
import com.amazonaws.services.stepfunctions.model.SendTaskFailureRequest;
import com.amazonaws.services.stepfunctions.model.SendTaskSuccessRequest;
import com.amazonaws.util.json.Jackson;
import com.fasterxml.jackson.databind.JsonNode;
import java.util.concurrent.TimeUnit;


public class GreeterActivities {

    public String getGreeting(String who) throws Exception {
        return "{\"Hello\": \"" + who + "\"}";
    }

    public static void main(final String[] args) throws Exception {
        GreeterActivities greeterActivities = new GreeterActivities();
        ClientConfiguration clientConfiguration = new ClientConfiguration();
        clientConfiguration.setSocketTimeout((int)TimeUnit.SECONDS.toMillis(70));

        AWSStepFunctions client = AWSStepFunctionsClientBuilder.standard()
                .withRegion(Regions.US_EAST_1)
                .withCredentials(new EnvironmentVariableCredentialsProvider())
                .withClientConfiguration(clientConfiguration)
                .build();

        while (true) {
            GetActivityTaskResult getActivityTaskResult =
                    client.getActivityTask(
                            new GetActivityTaskRequest().withActivityArn(ACTIVITY_ARN));

            if (getActivityTaskResult.getTaskToken() != null) {
                try {
                    JsonNode json = Jackson.jsonNodeOf(getActivityTaskResult.getInput());
                    String greetingResult =
                            greeterActivities.getGreeting(json.get("who").textValue());
                    client.sendTaskSuccess(
                            new SendTaskSuccessRequest().withOutput(
                                    greetingResult).withTaskToken(getActivityTaskResult.getTaskToken()));
                } catch (Exception e) {
                    client.sendTaskFailure(new SendTaskFailureRequest().withTaskToken(
                            getActivityTaskResult.getTaskToken()));
                }
            } else {
                Thread.sleep(1000);
            }
        }
    }
}

In the parameter list of the GetActivityTaskRequest().withActivityArn() constructor, replace the ACTIVITY_ARN value with the ARN of the activity task that you created earlier.

On the ActivityStateMachine page, choose Start execution.

The New execution page is displayed.

(Optional) To identify your execution, you can specify a name for it in the Name box. By default, Step Functions generates a unique execution name automatically.

In the execution input area, replace the example data with the following.

{
    "who" : "Amazon Step Functions"
}

Choose Start Execution.

A new execution of your state machine starts, and a new page showing your running execution is displayed.

In the Execution Details section, choose Info to view the Execution Status and the Started and Closed timestamps.

In the Execution Details section, expand the Output section to view the output of your workflow.

On the command line, navigate to the directory in which you created GreeterActivities.java.

To use the Amazon SDK, add the full path of the lib and third-party directories to the dependencies of your build file and to your Java CLASSPATH. For more information, see Downloading and Extracting the SDK in the Amazon SDK for Java Developer Guide.

Compile the file.

$ javac GreeterActivities.java

Run the file.

$ java GreeterActivities

In the Step Functions console, navigate to the Execution Details page.

When the execution completes, choose Output to see the results of your execution.

Stop the worker.