Hello,
Please review this small doc changes to more explicitly discuss the
special handling of enum types by serialization:
JDK-8234381: API docs should mention special handling of enums in
serialization
http://cr.openjdk.java.net/~darcy/8234381.0/
Patch below; thanks,
-Joe
--- old/src/java.base/share/classes/java/io/Serializable.java 2019-11-19
10:17:45.803443000 -0800
+++ new/src/java.base/share/classes/java/io/Serializable.java 2019-11-19
10:17:45.399241001 -0800
@@ -134,6 +134,11 @@
* This readResolve method follows the same invocation rules and
* accessibility rules as writeReplace.<p>
*
+ * <p>Enum types are all serializable and receive treatment defined by
+ * the <cite>Java Object Serialization Specification</cite> during
+ * serialization and deserialization. Any declarations of the special
+ * handling methods discussed above are ignored for enum types.
+ *
* The serialization runtime associates with each serializable class a
version
* number, called a serialVersionUID, which is used during
deserialization to
* verify that the sender and receiver of a serialized object have loaded
@@ -152,8 +157,9 @@
* If a serializable class does not explicitly declare a
serialVersionUID, then
* the serialization runtime will calculate a default serialVersionUID
value
* for that class based on various aspects of the class, as described
in the
- * Java(TM) Object Serialization Specification. However, it is
<em>strongly
- * recommended</em> that all serializable classes explicitly declare
+ * Java Object Serialization Specification. This specification defines the
+ * serialVersionUID of an enum type to be 0L. However, it is <em>strongly
+ * recommended</em> that all serializable classes other than enum types
explicitly declare
* serialVersionUID values, since the default serialVersionUID
computation is
* highly sensitive to class details that may vary depending on compiler
* implementations, and can thus result in unexpected
--- old/src/java.base/share/classes/java/lang/Enum.java 2019-11-19
10:17:46.807945000 -0800
+++ new/src/java.base/share/classes/java/lang/Enum.java 2019-11-19
10:17:46.371727000 -0800
@@ -47,6 +47,13 @@
* found in section 8.9 of
* <cite>The Java™ Language Specification</cite>.
*
+ * Enumeration types are all serializable and receive special handling
+ * by the serialization mechanism. The serialized representation used
+ * for enum constants cannot be customized. Declarations of methods
+ * and fields that would otherwise interact with serialization are
+ * ignored, including {@code serialVersionUID}; see the <cite>Java
+ * Object Serialization Specification</cite> for details.
+ *
* <p> Note that when using an enumeration type as the type of a set
* or as the type of the keys in a map, specialized and efficient
* {@linkplain java.util.EnumSet set} and {@linkplain
