--- java/org/apache/tomcat/util/buf/B2CConverter.java	(revision 1138858)
+++ java/org/apache/tomcat/util/buf/B2CConverter.java	(working copy)
@@ -23,9 +23,9 @@ 
 import java.io.InputStreamReader;
 import java.io.UnsupportedEncodingException;
 import java.nio.charset.Charset;
-import java.nio.charset.IllegalCharsetNameException;
-import java.nio.charset.UnsupportedCharsetException;
-import java.util.concurrent.ConcurrentHashMap;
+import java.util.HashMap;
+import java.util.Map.Entry;
+import java.util.SortedMap;
 
 /** Efficient conversion of bytes  to character .
  *  
@@ -44,28 +44,26 @@ 
     private static final org.apache.juli.logging.Log log=
         org.apache.juli.logging.LogFactory.getLog( B2CConverter.class );
     
-    private static final ConcurrentHashMap<String, Charset> encodingToCharsetCache =
-        new ConcurrentHashMap<String, Charset>();
+    private static final HashMap<String, Charset> encodingToCharsetCache =
+        new HashMap<String, Charset>();
+    
+    static {
+        SortedMap<String, Charset> charsets = Charset.availableCharsets();
+        for (Entry<String, Charset> e : charsets.entrySet()) {
+            Charset cs = e.getValue();
+            encodingToCharsetCache.put(e.getKey().toLowerCase(), cs);
+            for (String alias : cs.aliases()) {
+                encodingToCharsetCache.put(alias.toLowerCase(), cs);
+            }
+        }
+    }
 
     public static Charset getCharset(String enc)
             throws UnsupportedEncodingException{
-
-        Charset charset = encodingToCharsetCache.get(enc);
+        
+        Charset charset = encodingToCharsetCache.get(enc.toLowerCase());
         if (charset == null) {
-            try {
-                charset = Charset.forName(enc);
-            } catch (IllegalCharsetNameException icne) {
-                UnsupportedEncodingException uee =
-                    new UnsupportedEncodingException();
-                uee.initCause(icne);
-                throw uee;
-            } catch (UnsupportedCharsetException uce) {
-                UnsupportedEncodingException uee =
-                    new UnsupportedEncodingException();
-                uee.initCause(uce);
-                throw uee;
-            }
-            encodingToCharsetCache.put(enc, charset);
+            throw new UnsupportedEncodingException(enc);
         }
         return charset;
     }