Package com.google.cloud.functions

Interface RawBackgroundFunction

  • 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 RawBackgroundFunction
    Represents a Cloud Function that is activated by an event. The payload of the event is a JSON object, which can be parsed using a JSON package such as GSON.

    Here is an example of an implementation that parses the JSON payload using Gson, to access its messageId property: 

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

  @Override
   public void accept(String json, Context context) {
     JsonObject jsonObject = new Gson().fromJson(json, JsonObject.class);
     JsonElement messageId = jsonObject.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, again using Gson: 

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

  @Override
   public void accept(String json, Context context) {
     PubSubMessage message = new 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 Detail

      • accept

        void accept​(java.lang.String json,
            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:
        json - the payload of the event, as a 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.