adding option to have an inbound event filter in the default event inbound pipeline

Author: Micha Kiener

modules/flowable-event-registry-api/src/main/java/org/flowable/eventregistry/api/InboundEventFilter.java

@@ -0,0 +1,40 @@
+/* Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.flowable.eventregistry.api;
+
+/**
+ * This interface must be implemented by a custom filtering bean to hook into the default inbound event processing
+ * pipeline in order to have a very effective way to filter out events which should not be processed any further and
+ * thus preventing expensive processing time like DB lookups and the full consumer invocation.
+ *
+ * @param <T> the type of the expected payload (e.g. a JsonNode)
+ *
+ * @author Micha Kiener
+ */
+@FunctionalInterface
+public interface InboundEventFilter<T> {
+
+    /**
+     * Returns true, if the event should be further processed or false, if the event can be ignored and will not be processed
+     * any further and the pipeline will stop afterwards.
+     *
+     * @param payload the payload  of the event
+     * @return true, if the event should continue to be processed, false, if the pipeline will ignore the event and stop any
+     *      further processing
+     */
+    boolean filter(T payload);
+
+    default boolean filter(FlowableEventInfo<T> event) {
+        return filter(event.getPayload());
+    }
+}

modules/flowable-event-registry-api/src/main/java/org/flowable/eventregistry/api/model/InboundChannelModelBuilder.java

@@ -214,6 +214,12 @@ interface InboundEventProcessingPipelineBuilder {
          */
         InboundEventKeyXmlDetectorBuilder xmlDeserializer();
 
+        /**
+         * Uses a delegate expression to filter the events before further processing.
+         * The expression needs to resolve to a bean implementing the {@link org.flowable.eventregistry.api.InboundEventFilter} interface.
+         */
+        InboundEventProcessingPipelineBuilder delegateExpressionEventFilter(String delegateExpression);
+
         /**
          * Uses a delegate expression to deserialize the event.
          */

modules/flowable-event-registry-json-converter/src/test/java/org/flowable/eventregistry/converter/channel/JmsInboundChannelJsonConverterTest.java

@@ -53,6 +53,8 @@ protected void validateModel(ChannelModel channelModel) {
                 assertThat(model.getDestination()).isEqualTo("customer");
                 assertThat(model.getDeserializerType()).isEqualTo("json");
 
+                assertThat(model.getEventFilterDelegateExpression()).isEqualTo("testEventFilterExpression");
+
                 ChannelEventKeyDetection eventKeyDetection = model.getChannelEventKeyDetection();
                 assertThat(eventKeyDetection).isNotNull();
                 assertThat(eventKeyDetection.getFixedValue()).isNull();

modules/flowable-event-registry-json-converter/src/test/java/org/flowable/eventregistry/converter/channel/KafkaInboundChannelJsonConverterTest.java

@@ -52,6 +52,8 @@ protected void validateModel(ChannelModel channelModel) {
 
                 assertThat(model.getDeserializerType()).isEqualTo("json");
 
+                assertThat(model.getEventFilterDelegateExpression()).isEqualTo("testEventFilterExpression");
+
                 ChannelEventKeyDetection eventKeyDetection = model.getChannelEventKeyDetection();
                 assertThat(eventKeyDetection).isNotNull();
                 assertThat(eventKeyDetection.getFixedValue()).isNull();

modules/flowable-event-registry-json-converter/src/test/java/org/flowable/eventregistry/converter/channel/RabbitInboundChannelJsonConverterTest.java

@@ -52,6 +52,8 @@ protected void validateModel(ChannelModel channelModel) {
 
                 assertThat(model.getDeserializerType()).isEqualTo("json");
 
+                assertThat(model.getEventFilterDelegateExpression()).isEqualTo("testEventFilterExpression");
+
                 ChannelEventKeyDetection eventKeyDetection = model.getChannelEventKeyDetection();
                 assertThat(eventKeyDetection).isNotNull();
                 assertThat(eventKeyDetection.getFixedValue()).isNull();

modules/flowable-event-registry-json-converter/src/test/resources/org/flowable/eventregistry/converter/channel/simpleJmsInboundChannel.json

@@ -10,6 +10,7 @@
   "subscription": "testSubscription",
   "concurrency": "3",
   "deserializerType": "json",
+  "eventFilterDelegateExpression": "testEventFilterExpression",
   "channelEventKeyDetection": {
     "jsonField": "eventKey"
   }

modules/flowable-event-registry-json-converter/src/test/resources/org/flowable/eventregistry/converter/channel/simpleKafkaInboundChannel.json

@@ -21,6 +21,8 @@
     }
   ],
 
+  "eventFilterDelegateExpression": "testEventFilterExpression",
+
   "deserializerType": "json",
   "channelEventKeyDetection": {
     "jsonField": "eventKey"

modules/flowable-event-registry-json-converter/src/test/resources/org/flowable/eventregistry/converter/channel/simpleRabbitInboundChannel.json

@@ -18,6 +18,8 @@
   "executor": "rabbitTaskExecutor",
   "ackMode": "NONE",
 
+  "eventFilterDelegateExpression": "testEventFilterExpression",
+
   "deserializerType": "json",
   "channelEventKeyDetection": {
     "jsonField": "eventKey"

modules/flowable-event-registry-model/src/main/java/org/flowable/eventregistry/model/InboundChannelModel.java

@@ -23,6 +23,7 @@ public class InboundChannelModel extends ChannelModel {
 
     protected String contextExtractorDelegateExpression;
     protected String deserializerDelegateExpression;
+    protected String eventFilterDelegateExpression;
     protected String payloadExtractorDelegateExpression;
     protected String headerExtractorDelegateExpression;
     protected String eventTransformerDelegateExpression;
@@ -48,6 +49,14 @@ public void setDeserializerType(String deserializerType) {
         this.deserializerType = deserializerType;
     }
 
+    public String getEventFilterDelegateExpression() {
+        return eventFilterDelegateExpression;
+    }
+
+    public void setEventFilterDelegateExpression(String eventFilterDelegateExpression) {
+        this.eventFilterDelegateExpression = eventFilterDelegateExpression;
+    }
+
     public String getContextExtractorDelegateExpression() {
         return contextExtractorDelegateExpression;
     }

modules/flowable-event-registry/src/main/java/org/flowable/eventregistry/impl/model/InboundChannelDefinitionBuilderImpl.java

@@ -340,6 +340,12 @@ public InboundEventKeyXmlDetectorBuilder xmlDeserializer() {
             return new InboundEventKeyXmlDetectorBuilderImpl(xmlPipelineBuilder);
         }
 
+        @Override
+        public InboundEventProcessingPipelineBuilder delegateExpressionEventFilter(String delegateExpression) {
+            channelModel.setEventFilterDelegateExpression(delegateExpression);
+            return this;
+        }
+
         @Override
         public InboundEventKeyDetectorBuilder delegateExpressionDeserializer(String delegateExpression) {
             channelModel.setDeserializerType("expression");