Index: C:/Documents and Settings/Maarten Winkels/workspace/xstream/src/java/com/thoughtworks/xstream/mapper/ClassAliasingMapper.java
===================================================================
--- C:/Documents and Settings/Maarten Winkels/workspace/xstream/src/java/com/thoughtworks/xstream/mapper/ClassAliasingMapper.java	(revision 639)
+++ C:/Documents and Settings/Maarten Winkels/workspace/xstream/src/java/com/thoughtworks/xstream/mapper/ClassAliasingMapper.java	(working copy)
@@ -1,11 +1,17 @@
 package com.thoughtworks.xstream.mapper;
 
-import com.thoughtworks.xstream.alias.ClassMapper;
-
-import java.util.Map;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
 
+import org.apache.commons.lang.ClassUtils;
+
+import com.thoughtworks.xstream.alias.CannotResolveClassException;
+import com.thoughtworks.xstream.alias.ClassMapper;
+
 /**
  * Mapper that allows a fully qualified class name to be replaced with a shorter alias.
  *
@@ -15,22 +21,34 @@
 
     protected final Map typeToNameMap = Collections.synchronizedMap(new HashMap());
     protected final Map nameToTypeMap = Collections.synchronizedMap(new HashMap());
+    protected final List defaultPackages = Collections.synchronizedList(new ArrayList());
 
     public ClassAliasingMapper(ClassMapper wrapped) {
         super(wrapped);
     }
 
     public void addClassAlias(String name, Class type) {
-        nameToTypeMap.put(name, type.getName());
-        typeToNameMap.put(type.getName(), name);
+		doStore(name, type.getName());
     }
 
+	private void doStore(String alias, String className) {
+		nameToTypeMap.put(alias, className);
+        typeToNameMap.put(className, alias);
+	}
+
     public String serializedClass(Class type) {
         String name = super.serializedClass(type);
         String alias = (String) typeToNameMap.get(type.getName());
         if (alias != null) {
             return alias;
         } else {
+        	Package p = type.getPackage();
+			if (p != null && defaultPackages.contains(p.getName())) {
+        		String result = ClassUtils.getShortClassName(type);
+				// Store for future fast access.
+        		addClassAlias(result, type);
+				return result;
+        	}
             return name;
         }
     }
@@ -45,8 +63,28 @@
         if (mappedName != null) {
             elementName = mappedName;
         }
-
-        return super.realClass(elementName);
+    	try {
+            return super.realClass(elementName);
+    	} catch (CannotResolveClassException e) {
+    		//Last resort, try default packages.
+	    	for (Iterator i = defaultPackages.iterator(); i.hasNext();) {
+	    		StringBuffer prefix = new StringBuffer((String) i.next()).append('.');
+				try {
+					String className = prefix.append(elementName).toString();
+					Class type = super.realClass(className);
+					// Store for future fast access.
+					doStore(elementName,className);
+					return type;
+				} catch (CannotResolveClassException f) {
+					// Not found in this package, try next. Silently ignore
+				}
+			}
+	    	//Cannot find, rethrow.
+	    	throw e;
+    	}
     }
 
+	public void addPackage(Package p) {
+		defaultPackages.add(p.getName());
+	}
 }