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 Detail

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.