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Skill Attributes

Attributes

The SDK allows you to store and retrieve attributes at different scopes. You can use the attributes to, for example, store data that you retrieve on subsequent requests. You can also use attributes in handler canHandle logic to influence request routing.

An attribute consists of a key and a value. The key is enforced as a String type and the value is an unbounded Object. For session and persistent attributes, you must ensure that value types are serializable so they can be properly stored for subsequent retrieval. This restriction does not apply to request-level attributes because they do not persist outside of the request processing lifecycle.

Attribute Scopes

Request attributes

Request attributes only last within a single request processing lifecycle. Request attributes are initially empty when a request comes in, and are discarded once a response has been produced.

Request attributes are useful with request and response interceptors. For example, you can inject additional data and helper classes into request attributes through a request interceptor so they are retrievable by request handlers.

Session attributes

Session attributes persist throughout the lifespan of the current skill session. Session attributes are available for use with any in-session request. Any attributes set during the request processing lifecycle are sent back to the Alexa service and provided via the next request in the same session.

Session attributes do not require the use of an external storage solution. They are not available for use when handling out-of-session requests.

Persistent attributes

Persistent attributes persist beyond the lifecycle of the current session. How these attributes are stored, including key scope (user ID or device ID), TTL, and storage layer depends on the configuration of the skill.

Persistent attributes are only available when you configure the skill instance with a PersistenceAdapter. Calls to the AttributesManager to retrieve and save persistent attributes throw an IllegalStateException if a PersistenceAdapter has not been configured. Call savePersistentAttributes() on the AttributesManager to save any changes back to the persistence layer. Call deletePersistentAttributes() on the AttributesManager to delete the attributes from persistence layer.

AttributesManager

The AttributesManager exposes attributes that you can retrieve and update in your handlers. AttributesManager is available to handlers via the HandlerInput container class. The AttributesManager takes care of attributes retrieval and saving so that you can interact directly with attributes needed by your skill.

The following example shows how you can retrieve and save persistent attributes.

@Override
public boolean canHandle(HandlerInput input) {
    Map<String, Object> persistentAttributes = handlerInput.getAttributesManager().getPersistentAttributes();
    return persistentAttributes.get("foo").equals("bar");
}

@Override
public Optional<Response> handle(HandlerInput input) {
    Map<String, Object> persistentAttribues = handlerInput.getAttributesManager().getPersistentAttributes();
    persistentAttributes.put("foo", "baz");
    return Optional.empty();
}