# AWS Flow Framework for Java Annotations
**Topics**
+ [@Activities](#annotations-activities)
+ [@Activity](#annotations-activity)
+ [@ActivityRegistrationOptions](#annotations-activityregistration)
+ [@Asynchronous](#annotations-asynchronous)
+ [@Execute](#annotations-execute)
+ [@ExponentialRetry](#annotations-exponentialretry)
+ [@GetState](#annotations-getstate)
+ [@ManualActivityCompletion](#annotations-manualactivitycompletion)
+ [@Signal](#annotations-signal)
+ [@SkipRegistration](#annotations-skipregistration)
+ [@Wait and @NoWait](#annotations-waitnowait)
+ [@Workflow](#annotations-workflow)
+ [@WorkflowRegistrationOptions](#annotations-workflowregistrationoptions)
## @Activities
This annotation can be used on an interface to declare a set of activity types. Each method in an interface annotated with this annotation represents an activity type. An interface can't have both `@Workflow` and `@Activities` annotations-
The following parameters can be specified on this annotation:
`activityNamePrefix`
Specifies the prefix of the name of the activity types declared in the interface. If set to an empty string (which is the default), the name of the interface followed by '.' is used as the prefix.
`version`
Specifies the default version of the activity types declared in the interface. The default value is `1.0`.
`dataConverter`
Specifies the type of the `DataConverter` to use for serializing/deserializing data when creating tasks of this activity type and its results. Set to `NullDataConverter` by default, which indicates that the `JsonDataConverter` should be used.
## @Activity
This annotation can be used on methods within an interface annotated with `@Activities`.
The following parameters can be specified on this annotation:
`name`
Specifies the name of the activity type. The default is an empty string, which indicates that the default prefix and the activity method name should be used to determine the name of the activity type (which is of the form \$1*prefix*\$1\$1*name*\$1). Note that when you specify a name in an `@Activity` annotation, the framework will not automatically prepend a prefix to it. You are free to use your own naming scheme.
`version`
Specifies the version of the activity type. This overrides the default version specified in the `@Activities` annotation on the containing interface. The default is an empty string.
## @ActivityRegistrationOptions
Specifies the registration options of an activity type. This annotation can be used on an interface annotated with `@Activities` or the methods within. If specified in both places, then the annotation used on the method takes effect.
The following parameters can be specified on this annotation:
`defaultTasklist`
Specifies the default task list to be registered with Amazon SWF for this activity type. This default can be overridden when calling the activity method on the generated client using the `ActivitySchedulingOptions` parameter. Set to `USE_WORKER_TASK_LIST` by default. This is a special value which indicates that the task list used by the worker, which is performing the registration, should be used.
`defaultTaskScheduleToStartTimeoutSeconds`
Specifies the defaultTaskScheduleToStartTimeout registered with Amazon SWF for this activity type. This is the maximum time a task of this activity type is allowed to wait before it is assigned to a worker. See the *Amazon Simple Workflow Service API Reference* for more details.
`defaultTaskHeartbeatTimeoutSeconds`
Specifies the `defaultTaskHeartbeatTimeout` registered with Amazon SWF for this activity type. Activity workers must provide heartbeat within this duration; otherwise, the task will be timed out. Set to -1 by default, which is a special value that indicates this timeout should be disabled. See the *Amazon Simple Workflow Service API Reference* for more details.
`defaultTaskStartToCloseTimeoutSeconds`
Specifies the defaultTaskStartToCloseTimeout registered with Amazon SWF for this activity type. This timeout determines the maximum time a worker can take to process an activity task of this type. See the *Amazon Simple Workflow Service API Reference* for more details.
`defaultTaskScheduleToCloseTimeoutSeconds`
Specifies the `defaultScheduleToCloseTimeout` registered with Amazon SWF for this activity type. This timeout determines the total duration that the task can stay in open state. Set to -1 by default, which is a special value that indicates this timeout should be disabled. See the *Amazon Simple Workflow Service API Reference* for more details.
## @Asynchronous
When used on a method in the workflow coordination logic, indicates that the method should be executed asynchronously. A call to the method will return immediately, but the actual execution will happen asynchronously when all Promise<> parameters passed to the methods become ready. Methods annotated with @Asynchronous must have a return type of Promise<> or void.
`daemon`
Indicates if the task created for the asynchronous method should be a daemon task. `False` by default.
## @Execute
When used on a method in an interface annotated with the `@Workflow` annotation, identifies the entry point of the workflow.
**Important**
Only one method in the interface can be decorated with `@Execute`.
The following parameters can be specified on this annotation:
`name`
Specifies the name of the workflow type. If not set, the name defaults to \$1*prefix*\$1\$1*name*\$1, where \$1*prefix*\$1 is the name of the workflow interface followed by a '.' and \$1*name*\$1 is the name of the `@Execute`-decorated method in the workflow.
`version`
Specifies the version of the workflow type.
## @ExponentialRetry
When used on an activity or asynchronous method, sets an exponential retry policy if the method throws an unhandled exception. A retry attempt is made after a back-off period, which is calculated by the power of the number of attempts.
The following parameters can be specified on this annotation:
`intialRetryIntervalSeconds`
Specifies the duration to wait before the first retry attempt. This value should not be greater than `maximumRetryIntervalSeconds` and `retryExpirationSeconds`.
`maximumRetryIntervalSeconds`
Specifies the maximum duration between retry attempts. Once reached, the retry interval is capped to this value. Set to -1 by default, which means unlimited duration.
`retryExpirationSeconds`
Specifies the duration after which exponential retry will stop. Set to -1 by default, which means there is no expiration.
`backoffCoefficient`
Specifies the coefficient used to calculate the retry interval. See [Exponential Retry Strategy](features-retry.md#features-retry-exponential).
`maximumAttempts`
Specifies the number of attempts after which exponential retry will stop. Set to -1 by default, which means there is no limit on the number of retry attempts.
`exceptionsToRetry`
Specifies the list of exception types that should trigger a retry. Unhandled exception of these types will not propagate further and the method will be retried after the calculated retry interval. By default, the list contains `Throwable`.
`excludeExceptions`
Specifies the list of exception types that should not trigger a retry. Unhandled exceptions of this type will be allowed to propagate. The list is empty by default.
## @GetState
When used on a method in an interface annotated with the `@Workflow` annotation, identifies that the method is used to retrieve the latest workflow execution state. There can be at most one method with this annotation in an interface with the `@Workflow` annotation. Methods with this annotation must not take any parameters and must have a return type other than `void`.
## @ManualActivityCompletion
This annotation can be used on an activity method to indicate that the activity task should not be completed when the method returns. The activity task will not be automatically completed and would need to be completed manually directly using the Amazon SWF API. This is useful for use cases where the activity task is delegated to some external system that isn't automated or requires human intervention to be completed.
## @Signal
When used on a method in an interface annotated with the `@Workflow` annotation, identifies a signal that can be received by executions of the workflow type declared by the interface. Use of this annotation is required to define a signal method.
The following parameters can be specified on this annotation:
`name`
Specifies the name portion of the signal name. If not set, the name of the method is used.
## @SkipRegistration
When used on an interface annotated with the `@Workflow` annotation, indicates that the workflow type should not be registered with Amazon SWF. One of `@WorkflowRegistrationOptions` and `@SkipRegistrationOptions` annotations must be used on an interface annotated with `@Workflow`, but not both.
## @Wait and @NoWait
These annotations can be used on a parameter of type `Promise<>` to indicate whether the AWS Flow Framework for Java should wait for it to become ready before executing the method. By default, `Promise<>` parameters passed into `@Asynchronous` methods must become ready before method execution occurs. In certain scenarios, it is necessary to override this default behavior. `Promise<>` parameters passed into `@Asynchronous` methods and annotated with `@NoWait` are not waited for.
Collections parameters (or subclasses of) that contain promises, such as `List>`, must be annotated with `@Wait` annotation. By default, the framework doesn't wait for the members of a collection.
## @Workflow
This annotation is used on an interface to declare a *workflow* type. An interface decorated with this annotation should contain exactly one method that is decorated with the [@Execute](#annotations-execute) annotation to declare an entry point for your workflow.
**Note**
An interface can't have both `@Workflow` and `@Activities` annotations declared at once; they are mutually exclusive.
The following parameters can be specified on this annotation:
`dataConverter`
Specifies which `DataConverter` to use when sending requests to, and receiving results from, workflow executions of this workflow type.
The default is `NullDataConverter` which, in turn, falls back to `JsonDataConverter` to process all request and response data as JavaScript Object Notation (JSON).
### Example
```
import com.amazonaws.services.simpleworkflow.flow.annotations.Execute;
import com.amazonaws.services.simpleworkflow.flow.annotations.Workflow;
import com.amazonaws.services.simpleworkflow.flow.annotations.WorkflowRegistrationOptions;
@Workflow
@WorkflowRegistrationOptions(defaultExecutionStartToCloseTimeoutSeconds = 3600)
public interface GreeterWorkflow {
@Execute(version = "1.0")
public void greet();
}
```
## @WorkflowRegistrationOptions
When used on an interface annotated with `@Workflow`, provides default settings used by Amazon SWF when registering the workflow type.
**Note**
Either `@WorkflowRegistrationOptions` or `@SkipRegistrationOptions` must be used on an interface annotated with `@Workflow`, but you can't specify both.
The following parameters can be specified on this annotation:
Description
An optional text description of the workflow type.
`defaultExecutionStartToCloseTimeoutSeconds`
Specifies the `defaultExecutionStartToCloseTimeout` registered with Amazon SWF for the workflow type. This is the total time that a workflow execution of this type can take to complete.
For more information about workflow timeouts, see [Amazon SWF Timeout Types](swf-timeout-types.md).
`defaultTaskStartToCloseTimeoutSeconds`
Specifies the `defaultTaskStartToCloseTimeout` registered with Amazon SWF for the workflow type. This specifies the time a single decision task for a workflow execution of this type can take to complete.
If you don't specify `defaultTaskStartToCloseTimeout`, it will default to 30 seconds.
For more information about workflow timeouts, see [Amazon SWF Timeout Types](swf-timeout-types.md).
`defaultTaskList`
The default task list used for decision tasks for executions of this workflow type. The default set here can be overridden by using `StartWorkflowOptions` when starting a workflow execution.
If you don't specify `defaultTaskList`, it will be set to `USE_WORKER_TASK_LIST` by default. This indicates that the task list used by the worker that is performing the workflow registration should be used.
`defaultChildPolicy`
Specifies the policy to use for child workflows if an execution of this type is terminated. The default value is `ABANDON`. The possible values are:
+ `ABANDON` – Allow the child workflow executions to keep running
+ `TERMINATE` – Terminate child workflow executions
+ `REQUEST_CANCEL` – Request cancellation of the child workflow executions