com.google.cloud.functions

Interface BackgroundFunction

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

Represents a Cloud Function that is activated by an event.

Here is an example of an implementation that operates on the JSON payload of the event directly:

 public class Example implements BackgroundFunction {
   private static final Logger logger = Logger.getLogger(Example.class.getName());

    @Override
   public void accept(JsonElement json, Context context) {
     JsonElement messageId = json.getAsJsonObject().get("messageId");
     String messageIdString = messageId.getAsJsonString();
     logger.info("Got messageId " + messageIdString);
   }
 }
 

Here is an example of an implementation that deserializes the JSON payload into a Java object for simpler access:

 public class Example implements BackgroundFunction {
   private static final Logger logger = Logger.getLogger(Example.class.getName());

    @Override
   public void accept(JsonElement json, Context context) {
     PubSubMessage message = Gson.fromJson(json, PubSubMessage.class);
     logger.info("Got messageId " + message.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 and Description
void	accept(com.google.gson.JsonElement json, Context context) Called to service an incoming event.

Method Detail

accept

void accept(com.google.gson.JsonElement json,
            Context context)

Called to service an incoming event. This interface is implemented by user code to provide the action for a given background function. (including any Error) then the HTTP response will have a 500 status code.

Parameters:

json - the payload of the event, as a parsed JSON object.

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.