Add a method in SimpleMixInResolver for future optimizations

1 files changed, 29 insertions, 0 deletions

diff --git a/src/main/java/com/fasterxml/jackson/databind/introspect/SimpleMixInResolver.java b/src/main/java/com/fasterxml/jackson/databind/introspect/SimpleMixInResolver.java
index a3c630a88..2e9560bda 100644
--- a/src/main/java/com/fasterxml/jackson/databind/introspect/SimpleMixInResolver.java
+++ b/src/main/java/com/fasterxml/jackson/databind/introspect/SimpleMixInResolver.java
@@ -99,4 +99,33 @@ public class SimpleMixInResolver
     public int localSize() {
         return (_localMixIns == null) ? 0 : _localMixIns.size();
     }
+
+    /**
+     * Method that may be called for optimization purposes, to see if calls to
+     * mix-in resolver may be avoided. Return value of {@code true} means that
+     * it is possible that a mix-in class will be found; {@code false} that no
+     * mix-in will ever be found. In latter case caller can avoid calls altogether.
+     *<p>
+     * Note that the reason for "empty" resolvers is to use "null object" for simplifying
+     * code.
+     *
+     * @return True, if this resolver MAY have mix-ins to apply; false if not (it
+     *   is "empty")
+     *
+     * @since 2.10.1
+     */
+    public boolean hasMixIns() {
+        if (_localMixIns == null) {
+            // if neither local mix-ins nor overrides, no mix-ins
+            if (_overrides == null) {
+                return false;
+            }
+            // or, if no local mix-ins and can delegate to resolver
+            if (_overrides instanceof SimpleMixInResolver) {
+                return ((SimpleMixInResolver) _overrides).hasMixIns();
+            }
+        }
+        // cannot rule out the possibility, so...
+        return true;
+    }
 }