Issue OpenLiberty#1929 - serialize reference with instead of ref

dev/com.ibm.ws.microprofile.openapi/src/com/ibm/ws/microprofile/openapi/impl/core/jackson/mixin/ExtensionsMixin.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2017 IBM Corporation and others.
+ * Copyright (c) 2017, 2018 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -16,6 +16,11 @@
 import com.fasterxml.jackson.annotation.JsonAnySetter;
 import com.fasterxml.jackson.annotation.JsonProperty;
 
+/**
+ * Define mix-in annotations to use for augmenting annotations that processable (serializable / deserializable) classes have.
+ * Mixing in is done when introspecting class annotations and properties.
+ * All annotations from mixinSource are taken to override annotations that target (or its supertypes) has.
+ */
 public abstract class ExtensionsMixin {
 
     @JsonAnyGetter
@@ -30,4 +35,7 @@ public abstract class ExtensionsMixin {
     @JsonProperty("default")
     public abstract void getDefaultValue();
 
+    @JsonProperty("$ref")
+    public abstract void getRef();
+
 }