From 60fe05eb7a32a4a178f4212da6a812c80cedce82 Mon Sep 17 00:00:00 2001
From: Henri Yandell <bayard@apache.org>
Date: Wed, 5 Sep 2007 10:13:49 +0000
Subject: [PATCH] Applying Jason Madden's patch from LANG-334 to provide
 enums.Enum with optimized thread safety. As Jason's used this in production I
 think it's fair to use it rather than the simpler
 Collections.synchronizedMap(..). I've also applied the patch to the enum.Enum

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@572930 13f79535-47bb-0310-9956-ffa450edef68
---
 .../org/apache/commons/lang/enum/Enum.java    | 23 +++++++++++------
 .../org/apache/commons/lang/enums/Enum.java   | 25 +++++++++++++------
 2 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/src/java/org/apache/commons/lang/enum/Enum.java b/src/java/org/apache/commons/lang/enum/Enum.java
index de57cc05c..89e9de267 100644
--- a/src/java/org/apache/commons/lang/enum/Enum.java
+++ b/src/java/org/apache/commons/lang/enum/Enum.java
@@ -256,7 +256,11 @@ public abstract class Enum implements Comparable, Serializable {
     /**
      * <code>Map</code>, key of class name, value of <code>Entry</code>.
      */
-    private static final Map cEnumClasses = new WeakHashMap();
+    private static Map cEnumClasses
+        // LANG-334: To avoid exposing a mutating map,
+        // we copy it each time we add to it. This is cheaper than
+        // using a synchronized map since we are almost entirely reads
+        = new WeakHashMap();
     
     /**
      * The string representation of the Enum.
@@ -349,12 +353,17 @@ private void init(String name) {
         if (ok == false) {
             throw new IllegalArgumentException("getEnumClass() must return a superclass of this class");
         }
-        
-        // create entry
-        Entry entry = (Entry) cEnumClasses.get(enumClass);
-        if (entry == null) {
-            entry = createEntry(enumClass);
-            cEnumClasses.put(enumClass, entry);
+
+        Entry entry;
+        synchronized( Enum.class ) { // LANG-334
+            // create entry
+            entry = (Entry) cEnumClasses.get(enumClass);
+            if (entry == null) {
+                entry = createEntry(enumClass);
+                Map myMap = new WeakHashMap( cEnumClasses );
+                myMap.put(enumClass, entry);
+                cEnumClasses = myMap;
+            }
         }
         if (entry.map.containsKey(name)) {
             throw new IllegalArgumentException("The Enum name must be unique, '" + name + "' has already been added");
diff --git a/src/java/org/apache/commons/lang/enums/Enum.java b/src/java/org/apache/commons/lang/enums/Enum.java
index 6fce6fbc3..c26c474c0 100644
--- a/src/java/org/apache/commons/lang/enums/Enum.java
+++ b/src/java/org/apache/commons/lang/enums/Enum.java
@@ -302,7 +302,11 @@ public abstract class Enum implements Comparable, Serializable {
     /**
      * <code>Map</code>, key of class name, value of <code>Entry</code>.
      */
-    private static final Map cEnumClasses = new WeakHashMap();
+    private static Map cEnumClasses
+        // LANG-334: To avoid exposing a mutating map,
+        // we copy it each time we add to it. This is cheaper than
+        // using a synchronized map since we are almost entirely reads
+        = new WeakHashMap();
     
     /**
      * The string representation of the Enum.
@@ -345,7 +349,7 @@ private static class Entry {
          * <p>Restrictive constructor.</p>
          */
         protected Entry() {
-          super();
+            super();
         }
     }
 
@@ -395,12 +399,17 @@ private void init(String name) {
         if (ok == false) {
             throw new IllegalArgumentException("getEnumClass() must return a superclass of this class");
         }
-        
-        // create entry
-        Entry entry = (Entry) cEnumClasses.get(enumClass);
-        if (entry == null) {
-            entry = createEntry(enumClass);
-            cEnumClasses.put(enumClass, entry);
+
+        Entry entry;
+        synchronized( Enum.class ) { // LANG-334
+            // create entry
+            entry = (Entry) cEnumClasses.get(enumClass);
+            if (entry == null) {
+                entry = createEntry(enumClass);
+                Map myMap = new WeakHashMap( cEnumClasses );
+                myMap.put(enumClass, entry);
+                cEnumClasses = myMap;
+            }
         }
         if (entry.map.containsKey(name)) {
             throw new IllegalArgumentException("The Enum name must be unique, '" + name + "' has already been added");