AWS Step Function Client for Spring

This library provides an easy way to write step function activity workers in a Spring based Java app.

Usage

Enable the client by adding @EnableStepFunctionClient to you application configuration.

import com.widewail.spring.stepfunctions.EnableStepFunctionClient;

@SpringBootApplication
@EnableStepFunctionClient
public class Application {

}

Configuration

AWS Step Functions allows a worker name to be specified when consuming a task. By default the worker name will be the hostname of the machine consuming the task. If you would like to use the EC2 instance ID instead of the hostname you can create an @EC2WorkerNameProvider bean instead. Both naming strategies allow for a prefix to be added to the worker name. This is controlable via the stepfunctions.client.workerName property.

stepfunctions.client.workerName=worker-app

Other configuration

If you need to customize the default ObjectMapper instance simply provide one of your own in the application context.

Handling activities

Define your activity handlers using the @ActivityHandler annotation. The input to the handler method will be the input to the activity. The method should then return the input to the next activity as its return value or throw an exception to fail the task. If the argument to a method is an object then the payload to the task will be deserialized accordingly. A String argument type will always receive the raw payload.

import com.widewail.spring.stepfunctions.ActivityHandler;

@ActivityHandler(arn = "arn:task1")
public String appendStuff(String input) {
    return input + "-stuff";
}

Handler methods can have the following signatures

R handle() - no args returning the output from the task.

R handle(T) - Receive the input from the task. Return the output from the task.

R handle(T, String) - receive the input from the task and the task token. Return the output from the task.

import com.widewail.spring.stepfunctions.ActivityHandler;

@ActivityHandler(arn = "arn:task2")
public String appendStuff(MyObject input, String taskToken) {
    //...
}

Handlers may also return a value of type ActivityResult to control the success/failure of a task.

import com.widewail.spring.stepfunctions.ActivityHandler;

@ActivityHandler(arn = "arn:task2")
public ActivityResult<String> doTheThing(String input) {
    //...
    if(success) {
        return ActivityResult.success("return payload");
    } else {
        return ActivityResult.fail("error message");
    }
}