SimpleKey contains invalid hashcode on deserialization when parameters include an enum

spring-context/src/main/java/org/springframework/cache/interceptor/SimpleKey.java

@@ -39,7 +39,21 @@ public class SimpleKey implements Serializable {
 
 	private final Object[] params;
 
-	private final int hashCode;
+	/**
+	 * The basic Object.hashCode functionality is to derive the hash code from
+	 * a runtime-specific object identity. This makes SimpleKey hash codes unsafe
+	 * to serialize and share with other JVM runtimes, since if the SimpleKey has
+	 * any parameters of an object type that uses an identity hash code, a hash
+	 * code received from another runtime will not match the hash code the
+	 * receiving runtime would produce for an equal SimpleKey instance.
+	 *
+	 * For most object types this is not likely to cause a problem because an
+	 * identity-based hash code implies an identity-based equals method, and objects
+	 * like that are unlikely to make good cache keys in the first place. But
+	 * enums are a big exception - they are singletons with special serialization
+	 * rules and are fine cache key parameters, but it is important not to
+	 * share their identity-based hash codes. */
+	private transient int hashCode;
 
 
 	/**
@@ -61,6 +75,10 @@ public boolean equals(@Nullable Object other) {
 
 	@Override
 	public final int hashCode() {
+		// If this instance was deserialized instead of constructed its hashCode may not be initialized.
+		if (this.hashCode == 0) {
+			this.hashCode = Arrays.deepHashCode(this.params);
+		}
 		return this.hashCode;
 	}