Store the class object itself (#4927)

* Store the class object itself

* Add test for backwards compatibility

* Rename and add test

* Add comments

1 files changed, 12 insertions, 4 deletions

diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index df01547e..1e122d16 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -1407,7 +1407,7 @@ public abstract class GeneratedMessageLite<
 
   /**
    * A serialized (serializable) form of the generated message.  Stores the
-   * message as a class name and a byte array.
+   * message as a class and a byte array.
    */
   protected static final class SerializedForm implements Serializable {
 
@@ -1417,6 +1417,9 @@ public abstract class GeneratedMessageLite<
 
     private static final long serialVersionUID = 0L;
 
+    // since v3.6.1
+    private final Class<?> messageClass;
+    // only included for backwards compatibility before messageClass was added
     private final String messageClassName;
     private final byte[] asBytes;
 
@@ -1425,7 +1428,8 @@ public abstract class GeneratedMessageLite<
      * @param regularForm the message to serialize
      */
     SerializedForm(MessageLite regularForm) {
-      messageClassName = regularForm.getClass().getName();
+      messageClass = regularForm.getClass();
+      messageClassName = messageClass.getName();
       asBytes = regularForm.toByteArray();
     }
 
@@ -1437,7 +1441,7 @@ public abstract class GeneratedMessageLite<
     @SuppressWarnings("unchecked")
     protected Object readResolve() throws ObjectStreamException {
       try {
-        Class<?> messageClass = Class.forName(messageClassName);
+        Class<?> messageClass = resolveMessageClass();
         java.lang.reflect.Field defaultInstanceField =
             messageClass.getDeclaredField("DEFAULT_INSTANCE");
         defaultInstanceField.setAccessible(true);
@@ -1464,7 +1468,7 @@ public abstract class GeneratedMessageLite<
     @Deprecated
     private Object readResolveFallback() throws ObjectStreamException {
       try {
-        Class<?> messageClass = Class.forName(messageClassName);
+        Class<?> messageClass = resolveMessageClass();
         java.lang.reflect.Field defaultInstanceField =
             messageClass.getDeclaredField("defaultInstance");
         defaultInstanceField.setAccessible(true);
@@ -1484,6 +1488,10 @@ public abstract class GeneratedMessageLite<
         throw new RuntimeException("Unable to understand proto buffer", e);
       }
     }
+
+    private Class<?> resolveMessageClass() throws ClassNotFoundException {
+      return messageClass != null ? messageClass : Class.forName(messageClassName);
+    }
   }
 
   /**