Avoid the event bus delivery context machinery when the interceptor chain is empty.

Motivation:

When the event-bus interceptor chain is empty we can skip the delivery context machinery that is not necessary as it involves creating garbage and atomics. This is possible due to a recent refactoring change.

Changes:

When the interceptor chain is obtained, bypass the delivery context machinery when the chain is empty.

Author: vietj

vertx-core/src/main/java/io/vertx/core/eventbus/impl/HandlerRegistration.java

@@ -11,6 +11,7 @@
 package io.vertx.core.eventbus.impl;
 
 import io.vertx.core.*;
+import io.vertx.core.eventbus.DeliveryContext;
 import io.vertx.core.eventbus.Message;
 import io.vertx.core.eventbus.ReplyException;
 import io.vertx.core.eventbus.ReplyFailure;
@@ -90,10 +91,15 @@ public Future<Void> unregister() {
     return promise.future();
   }
 
-  void dispatchMessage(Handler<Message<T>> theHandler, MessageImpl<?, T> message, ContextInternal context) {
-    Runnable dispatch = () -> dispatch(context, message, theHandler);
-    DeliveryContextImpl<T> deliveryCtx = new DeliveryContextImpl<>(message, message.bus.inboundInterceptors(), context, message.receivedBody, dispatch);
-    deliveryCtx.next();
+  void dispatchMessage(Handler<Message<T>> handler, MessageImpl<?, T> message, ContextInternal context) {
+    Handler<DeliveryContext<?>>[] interceptors = message.bus.inboundInterceptors();
+    if (interceptors.length > 0) {
+      Runnable dispatch = () -> dispatch(context, message, handler);
+      DeliveryContextImpl<T> deliveryCtx = new DeliveryContextImpl<>(message, interceptors, context, message.receivedBody, dispatch);
+      deliveryCtx.next();
+    } else {
+      dispatch(context, message, handler);
+    }
   }
 
   private void dispatch(ContextInternal ctx, MessageImpl<?, T> message, Handler<Message<T>> handler) {

vertx-core/src/main/java/io/vertx/core/eventbus/impl/SendContext.java

@@ -46,10 +46,14 @@ public class SendContext<T> implements Promise<Void> {
     this.writePromise = ctx.promise();
   }
 
-  public void send() {
+  void send() {
     Handler<DeliveryContext<?>>[] interceptors = message.bus.outboundInterceptors();
-    DeliveryContextImpl<T> deliveryContext = new DeliveryContextImpl<>(message, interceptors, ctx,  message.sentBody, this::execute);
-    deliveryContext.next();
+    if (interceptors.length > 0) {
+      DeliveryContextImpl<T> deliveryContext = new DeliveryContextImpl<>(message, interceptors, ctx,  message.sentBody, this::sendOrPub);
+      deliveryContext.next();
+    } else {
+      sendOrPub();
+    }
   }
 
   @Override
@@ -109,7 +113,7 @@ private void written(Throwable failure) {
     }
   }
 
-  protected void execute() {
+  private void sendOrPub() {
     VertxTracer tracer = ctx.tracer();
     if (tracer != null) {
       if (message.trace == null) {