From 5ad5f22e7c9991be7a20a33a51948e3ffd2a38c5 Mon Sep 17 00:00:00 2001
From: andrzej <andrzej@6335cc39-0255-0410-8fd6-9bcaacd3b74c>
Date: Wed, 11 Oct 2006 18:41:08 +0000
Subject: [PATCH] Added a method to create a Properties object that accesses
 subproperties by filtering a referenced base Properties, rather than creating
 an entirely new set of Properties, to avoid creating loads of garbage when
 filtering through multiple levels of subproperties.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1943 6335cc39-0255-0410-8fd6-9bcaacd3b74c
---
 .../com/samskivert/util/PropertiesUtil.java   | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/src/java/com/samskivert/util/PropertiesUtil.java b/src/java/com/samskivert/util/PropertiesUtil.java
index 672d5db9..0a3abfad 100644
--- a/src/java/com/samskivert/util/PropertiesUtil.java
+++ b/src/java/com/samskivert/util/PropertiesUtil.java
@@ -92,6 +92,38 @@ public class PropertiesUtil
         return dest;
     }
 
+    /**
+     * Returns a filtered version of the specified properties that first
+     * looks for a property starting with the given prefix, then looks for
+     * a property without the prefix.  For example, passing the prefix "alt"
+     * and using the following properties:
+     *
+     * <pre>
+     * alt.texture = sand.png
+     * lighting = off
+     * </pre>
+     *
+     * ...would return "sand.png" for the property "texture" and "off" for
+     * the property "lighting".  Unlike {@link #getSubProperties}, the object
+     * returned by this method references, rather than copies, the underlying
+     * properties.  Only the {@link Properties#getProperty} methods are
+     * guaranteed to work correctly on the returned object.
+     */
+    public static Properties getFilteredProperties (
+        final Properties source, String prefix)
+    {
+        final String dprefix = prefix + ".";
+        return new Properties() {
+            public String getProperty (String key) {
+                return getProperty(key, null);
+            }
+            public String getProperty (String key, String defaultValue) {
+                return source.getProperty(dprefix + key,
+                    source.getProperty(key, defaultValue));
+            }
+        };
+    }
+    
     /**
      * A helper function used by the {@link #getSubProperties} methods.
      */