Package com.google.cloud.functions

Interface BackgroundFunction<T>

Type Parameters:
T - the class of payload objects that this function expects.
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@FunctionalInterface
public interface BackgroundFunction<T>
Represents a Cloud Function that is activated by an event and parsed into a user-supplied class. The payload of the event is a JSON object, which is deserialized into a user-defined class as described for Gson.

Here is an example of an implementation that accesses the messageId property from a payload that matches a user-defined PubSubMessage class: 

 public class Example implementsBackgroundFunction<PubSubMessage> {
   private static final Logger logger = Logger.getLogger(Example.class.getName());

  @Override
   public void accept(PubSubMessage pubSubMessage, Context context) {
     logger.info("Got messageId " + pubSubMessage.messageId);
   }
 }

 // Where PubSubMessage is a user-defined class like this:
 public class PubSubMessage {
   String data;
  Map<String, String> attributes;
   String messageId;
   String publishTime;
 }

  • Method Summary

    Modifier and Type Method Description
    void accept​(T payload, Context context)
    Called to service an incoming event.

  • Method Details

    • accept

      void accept​(T payload, Context context) throws java.lang.Exception
      Called to service an incoming event. This interface is implemented by user code to provide the action for a given background function. If this method throws any exception (including any Error) then the HTTP response will have a 500 status code.
      Parameters:
      payload - the payload of the event, deserialized from the original JSON string.
      context - the context of the event. This is a set of values that every event has, separately from the payload, such as timestamp and event type.
      Throws:
      java.lang.Exception - to produce a 500 status code in the HTTP response.