From 5a1bd5aa58163b9eae1fe4d658fddda042b31cc6 Mon Sep 17 00:00:00 2001
From: Havoc Pennington <hp@pobox.com>
Date: Sun, 27 Nov 2011 01:59:04 -0500
Subject: [PATCH] use "SingletonHolder" pattern rather than synchronized in
 ConfigImpl

---
 .../com/typesafe/config/impl/ConfigImpl.java  | 57 +++++++++----------
 .../config/impl/ConfigSubstitutionTest.scala  |  2 +-
 2 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/config/src/main/java/com/typesafe/config/impl/ConfigImpl.java b/config/src/main/java/com/typesafe/config/impl/ConfigImpl.java
index cb0551ab..7c34b0d9 100644
--- a/config/src/main/java/com/typesafe/config/impl/ConfigImpl.java
+++ b/config/src/main/java/com/typesafe/config/impl/ConfigImpl.java
@@ -336,29 +336,26 @@ public class ConfigImpl {
         }
     }
 
-    private static ConfigIncluder defaultIncluder = null;
-
-    synchronized static ConfigIncluder defaultIncluder() {
-        if (defaultIncluder == null) {
-            defaultIncluder = new SimpleIncluder(null);
-        }
-        return defaultIncluder;
+    private static class DefaultIncluderHolder {
+        static final ConfigIncluder defaultIncluder = new SimpleIncluder(null);
     }
 
-    private static AbstractConfigObject systemProperties = null;
-
-    synchronized static AbstractConfigObject systemPropertiesAsConfigObject() {
-        if (systemProperties == null) {
-            systemProperties = loadSystemProperties();
-        }
-        return systemProperties;
+    static ConfigIncluder defaultIncluder() {
+        return DefaultIncluderHolder.defaultIncluder;
     }
 
     private static AbstractConfigObject loadSystemProperties() {
-        return (AbstractConfigObject) Parseable.newProperties(
-                System.getProperties(),
-                ConfigParseOptions.defaults().setOriginDescription(
-                        "system properties")).parse();
+        return (AbstractConfigObject) Parseable.newProperties(System.getProperties(),
+                ConfigParseOptions.defaults().setOriginDescription("system properties")).parse();
+    }
+
+    private static class SystemPropertiesHolder {
+        // this isn't final due to the reloadSystemPropertiesConfig() hack below
+        static AbstractConfigObject systemProperties = loadSystemProperties();
+    }
+
+    static AbstractConfigObject systemPropertiesAsConfigObject() {
+        return SystemPropertiesHolder.systemProperties;
     }
 
     /** For use ONLY by library internals, DO NOT TOUCH not guaranteed ABI */
@@ -366,18 +363,10 @@ public class ConfigImpl {
         return systemPropertiesAsConfigObject().toConfig();
     }
 
-    // this is a hack to let us set system props in the test suite
-    synchronized static void dropSystemPropertiesConfig() {
-        systemProperties = null;
-    }
-
-    private static AbstractConfigObject envVariables = null;
-
-    synchronized static AbstractConfigObject envVariablesAsConfigObject() {
-        if (envVariables == null) {
-            envVariables = loadEnvVariables();
-        }
-        return envVariables;
+    // this is a hack to let us set system props in the test suite.
+    // obviously not thread-safe.
+    static void reloadSystemPropertiesConfig() {
+        SystemPropertiesHolder.systemProperties = loadSystemProperties();
     }
 
     private static AbstractConfigObject loadEnvVariables() {
@@ -393,6 +382,14 @@ public class ConfigImpl {
                 m, ResolveStatus.RESOLVED, false /* ignoresFallbacks */);
     }
 
+    private static class EnvVariablesHolder {
+        static final AbstractConfigObject envVariables = loadEnvVariables();
+    }
+
+    static AbstractConfigObject envVariablesAsConfigObject() {
+        return EnvVariablesHolder.envVariables;
+    }
+
     /** For use ONLY by library internals, DO NOT TOUCH not guaranteed ABI */
     public static Config envVariablesAsConfig() {
         return envVariablesAsConfigObject().toConfig();
diff --git a/config/src/test/scala/com/typesafe/config/impl/ConfigSubstitutionTest.scala b/config/src/test/scala/com/typesafe/config/impl/ConfigSubstitutionTest.scala
index a051b5a4..8014d06c 100644
--- a/config/src/test/scala/com/typesafe/config/impl/ConfigSubstitutionTest.scala
+++ b/config/src/test/scala/com/typesafe/config/impl/ConfigSubstitutionTest.scala
@@ -257,7 +257,7 @@ class ConfigSubstitutionTest extends TestUtils {
     def fallbackToSystemProps() {
         System.setProperty("configtest.a", "1234")
         System.setProperty("configtest.b", "5678")
-        ConfigImpl.dropSystemPropertiesConfig()
+        ConfigImpl.reloadSystemPropertiesConfig()
 
         val resolved = resolve(substSystemPropsObject)