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 Summary

Modifier and Type	Method and Description
void	accept(String json, Context context) Called to service an incoming event.

Method Detail

accept

void accept(String json,
            Context context)
     throws 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:

Exception