feat: enable converting CloudEvent requests to Background Event requests (GoogleCloudPlatform#123)

This enables backwards compatability for GCF Background Functions with
newer CloudEvent-based eventing systems and brings FF Java up-to-date
with conformance tests.

Author: anniefu

.github/workflows/conformance.yaml

@@ -34,25 +34,28 @@ jobs:
       run: (cd invoker/ && mvn install)
 
     - name: Run HTTP conformance tests
-      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.0.0
+      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.2.1
       with:
+        version: 'v1.2.1'
         functionType: 'http'
         useBuildpacks: false
         cmd: "'mvn -f invoker/conformance/pom.xml function:run -Drun.functionTarget=com.google.cloud.functions.conformance.HttpConformanceFunction'"
         startDelay: 10
 
     - name: Run background event conformance tests
-      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.0.0
+      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.2.1
       with:
+        version: 'v1.2.1'
         functionType: 'legacyevent'
         useBuildpacks: false
-        validateMapping: false
+        validateMapping: true
         cmd: "'mvn -f invoker/conformance/pom.xml function:run -Drun.functionTarget=com.google.cloud.functions.conformance.BackgroundEventConformanceFunction'"
         startDelay: 10
 
     - name: Run cloudevent conformance tests
-      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.0.0
+      uses: GoogleCloudPlatform/functions-framework-conformance/action@v1.2.1
       with:
+        version: 'v1.2.1'
         functionType: 'cloudevent'
         useBuildpacks: false
         validateMapping: true

invoker/conformance/pom.xml

@@ -34,6 +34,16 @@
       <artifactId>gson</artifactId>
       <version>2.8.6</version>
     </dependency>
+    <dependency>
+      <groupId>io.cloudevents</groupId>
+      <artifactId>cloudevents-core</artifactId>
+      <version>2.2.0</version>
+    </dependency>
+    <dependency>
+      <groupId>io.cloudevents</groupId>
+      <artifactId>cloudevents-json-jackson</artifactId>
+      <version>2.2.0</version>
+    </dependency>
   </dependencies>
 
   <build>

invoker/conformance/src/main/java/com/google/cloud/functions/conformance/BackgroundEventConformanceFunction.java

@@ -40,8 +40,12 @@ private String serialize(String data, Context context) {
     contextJson.addProperty("timestamp", context.timestamp());
     contextJson.addProperty("eventType", context.eventType());
 
-    JsonElement resource = gson.fromJson(context.resource(), JsonElement.class);
-    contextJson.add("resource", resource);
+    if (context.resource().startsWith("{")) {
+      JsonElement resource = gson.fromJson(context.resource(), JsonElement.class);
+      contextJson.add("resource", resource);
+    } else {
+      contextJson.addProperty("resource", context.resource());
+    }
 
     JsonObject dataJson = gson.fromJson(data, JsonObject.class);
 

invoker/conformance/src/main/java/com/google/cloud/functions/conformance/CloudEventsConformanceFunction.java

@@ -17,13 +17,12 @@
 import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.cloud.functions.CloudEventsFunction;
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-import com.google.gson.JsonObject;
 import io.cloudevents.CloudEvent;
+import io.cloudevents.core.format.EventFormat;
+import io.cloudevents.core.provider.EventFormatProvider;
+import io.cloudevents.jackson.JsonFormat;
 import java.io.BufferedWriter;
 import java.io.FileWriter;
-import java.time.format.DateTimeFormatter;
 
 /**
  * This class is used by the Functions Framework Conformance Tools to validate the framework's Cloud
@@ -40,33 +39,11 @@
  */
 public class CloudEventsConformanceFunction implements CloudEventsFunction {
 
-  private static final Gson gson = new GsonBuilder().serializeNulls().setPrettyPrinting().create();
-
   @Override
   public void accept(CloudEvent event) throws Exception {
     try (BufferedWriter writer = new BufferedWriter(new FileWriter("function_output.json"))) {
-      writer.write(serialize(event));
+      EventFormat format = EventFormatProvider.getInstance().resolveFormat(JsonFormat.CONTENT_TYPE);
+      writer.write(new String(format.serialize(event), UTF_8));
     }
   }
-
-  /** Create a structured JSON representation of a cloud event */
-  private String serialize(CloudEvent event) {
-    JsonObject jsonEvent = new JsonObject();
-
-    jsonEvent.addProperty("id", event.getId());
-    jsonEvent.addProperty("source", event.getSource().toString());
-    jsonEvent.addProperty("type", event.getType());
-    jsonEvent.addProperty("datacontenttype", event.getDataContentType());
-    jsonEvent.addProperty("subject", event.getSubject());
-    jsonEvent.addProperty("specversion", event.getSpecVersion().toString());
-
-    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssXXX");
-    jsonEvent.addProperty("time", event.getTime().format(formatter));
-
-    String payloadJson = new String(event.getData().toBytes(), UTF_8);
-    JsonObject jsonObject = new Gson().fromJson(payloadJson, JsonObject.class);
-    jsonEvent.add("data", jsonObject);
-
-    return gson.toJson(jsonEvent);
-  }
 }

invoker/core/pom.xml

@@ -130,6 +130,11 @@
       <version>4.13.1</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>com.google.re2j</groupId>
+      <artifactId>re2j</artifactId>
+      <version>1.6</version>
+    </dependency>
     <dependency>
       <groupId>com.google.truth</groupId>
       <artifactId>truth</artifactId>

invoker/core/src/main/java/com/google/cloud/functions/invoker/BackgroundFunctionExecutor.java

@@ -14,7 +14,6 @@
 
 package com.google.cloud.functions.invoker;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.stream.Collectors.toList;
 import static java.util.stream.Collectors.toMap;
 
@@ -263,10 +262,7 @@ void serviceLegacyEvent(Event legacyEvent) throws Exception {
 
     @Override
     void serviceCloudEvent(CloudEvent cloudEvent) throws Exception {
-      Context context = contextFromCloudEvent(cloudEvent);
-      String jsonData =
-          (cloudEvent.getData() == null) ? "{}" : new String(cloudEvent.getData().toBytes(), UTF_8);
-      function.accept(jsonData, context);
+      serviceLegacyEvent(CloudEvents.convertToLegacyEvent(cloudEvent));
     }
   }
 
@@ -295,10 +291,7 @@ void serviceLegacyEvent(Event legacyEvent) throws Exception {
     @Override
     void serviceCloudEvent(CloudEvent cloudEvent) throws Exception {
       if (cloudEvent.getData() != null) {
-        String data = new String(cloudEvent.getData().toBytes(), UTF_8);
-        T payload = new Gson().fromJson(data, type);
-        Context context = contextFromCloudEvent(cloudEvent);
-        function.accept(payload, context);
+        serviceLegacyEvent(CloudEvents.convertToLegacyEvent(cloudEvent));
       } else {
         throw new IllegalStateException("Event has no \"data\" component");
       }