diff --git a/org.apache.felix.main/src/main/java/org/apache/felix/main/Main.java b/org.apache.felix.main/src/main/java/org/apache/felix/main/Main.java
index 33e9b6d..cb03a8f 100644
--- a/org.apache.felix.main/src/main/java/org/apache/felix/main/Main.java
+++ b/org.apache.felix.main/src/main/java/org/apache/felix/main/Main.java
@@ -19,8 +19,7 @@
 import java.io.*;
 import java.net.MalformedURLException;
 import java.net.URL;
-import java.util.Enumeration;
-import java.util.Properties;
+import java.util.*;
 
 import org.apache.felix.framework.Felix;
 import org.apache.felix.framework.cache.BundleCache;
@@ -298,11 +297,12 @@
             return;
         }
 
-        // Perform variable substitution for system properties.
+        // Perform variable substitution on specified properties.
         for (Enumeration e = props.propertyNames(); e.hasMoreElements(); )
         {
             String name = (String) e.nextElement();
-            System.setProperty(name, substVars((String) props.getProperty(name)));
+            System.setProperty(name,
+                substVars(props.getProperty(name), name, null, null));
         }
     }
 
@@ -410,81 +410,134 @@
         for (Enumeration e = props.propertyNames(); e.hasMoreElements(); )
         {
             String name = (String) e.nextElement();
-            props.setProperty(name, substVars((String) props.getProperty(name)));
+            props.setProperty(name,
+                substVars(props.getProperty(name), name, null, props));
         }
 
         return props;
     }
 
     private static final String DELIM_START = "${";
-    private static final char DELIM_STOP  = '}';
-    private static final int DELIM_START_LEN = 2;
-    private static final int DELIM_STOP_LEN  = 1;
+    private static final String DELIM_STOP  = "}";
 
     /**
      * <p>
-     * This method performs system property variable substitution on the
-     * specified string value. If the specified string contains the
-     * syntax <tt>${&lt;system-prop-name&gt;}</tt>, then the corresponding
-     * system property value is substituted for the marker.
+     * This method performs property variable substitution on the
+     * specified value. If the specified value contains the syntax
+     * <tt>${&lt;prop-name&gt;}</tt>, where <tt>&lt;prop-name&gt;</tt>
+     * refers to either a configuration property or a system property,
+     * then the corresponding property value is substituted for the variable
+     * placeholder. Multiple variable placeholders may exist in the
+     * specified value as well as nested variable placeholders, which
+     * are substituted from inner most to outer most. Configuration
+     * properties override system properties.
      * </p>
-     * @param val The string on which to perform system property substitution.
+     * @param val The string on which to perform property substitution.
+     * @param currentKey The key of the property being evaluated used to
+     *        detect cycles.
+     * @param cycleMap Map of variable references used to detect nested cycles.
+     * @param configProps Set of configuration properties.
      * @return The value of the specified string after system property substitution.
      * @throws IllegalArgumentException If there was a syntax error in the
-     *         system property variable marker syntax.
+     *         property placeholder syntax or a recursive variable reference.
     **/
-    public static String substVars(String val)
+    public static String substVars(String val, String currentKey,
+        Map cycleMap, Properties configProps)
         throws IllegalArgumentException
     {
-        StringBuffer sbuf = new StringBuffer();
+        // If there is currently no cycle map, then create
+        // one for detecting cycles for this invocation.
+        if (cycleMap == null)
+        {
+            cycleMap = new HashMap();
+        }
+    
+        // Put the current key in the cycle map.
+        cycleMap.put(currentKey, currentKey);
+    
+        // Assume we have a value that is something like:
+        // "leading ${foo.${bar}} middle ${baz} trailing"
 
-        if (val == null)
+        // Find the first ending '}' variable delimiter, which
+        // will correspond to the first deepest nested variable
+        // placeholder.
+        int stopDelim = val.indexOf(DELIM_STOP);
+
+        // Find the matching starting "${" variable delimiter
+        // by looping until we find a start delimiter that is
+        // greater than the stop delimiter we have found.
+        int startDelim = val.indexOf(DELIM_START);
+        while (stopDelim >= 0)
+        {
+            int idx = val.indexOf(DELIM_START, startDelim + DELIM_START.length());
+            if ((idx < 0) || (idx > stopDelim))
+            {
+                break;
+            }
+            else if (idx < stopDelim)
+            {
+                startDelim = idx;
+            }
+        }
+
+        // If we do not have a start or stop delimiter, then just
+        // return the existing value.
+        if ((startDelim < 0) && (stopDelim < 0))
         {
             return val;
         }
-
-        int i = 0;
-        int j, k;
-
-        while (true)
+        // At this point, we found a stop delimiter without a start,
+        // so throw an exception.
+        else if (((startDelim < 0) || (startDelim > stopDelim))
+            && (stopDelim >= 0))
         {
-            j = val.indexOf(DELIM_START, i);
-            if (j == -1)
-            {
-                if (i == 0)
-                {
-                    return val;
-                }
-                else
-                {
-                    sbuf.append(val.substring(i, val.length()));
-                    return sbuf.toString();
-                }
-            }
-            else
-            {
-                sbuf.append(val.substring(i, j));
-                k = val.indexOf(DELIM_STOP, j);
-                if (k == -1)
-                {
-                    throw new IllegalArgumentException(
-                    '"' + val +
-                    "\" has no closing brace. Opening brace at position "
-                    + j + '.');
-                }
-                else
-                {
-                    j += DELIM_START_LEN;
-                    String key = val.substring(j, k);
-                    // Try system properties.
-                    String replacement = System.getProperty(key, null);
-                    if (replacement != null)
-                    {
-                        sbuf.append(replacement);
-                    }
-                    i = k + DELIM_STOP_LEN;
-                }
-            }
+            throw new IllegalArgumentException(
+                "stop delimiter with no start delimiter: "
+                + val);
         }
+
+        // At this point, we have found a variable placeholder so
+        // we must perform a variable substitution on it.
+        // Using the start and stop delimiter indices, extract
+        // the first, deepest nested variable placeholder.
+        String variable =
+            val.substring(startDelim + DELIM_START.length(), stopDelim);
+
+        // Verify that this is not a recursive variable reference.
+        if (cycleMap.get(variable) != null)
+        {
+            throw new IllegalArgumentException(
+                "recursive variable reference: " + variable);
+        }
+
+        // Get the value of the deepest nested variable placeholder.
+        // Try to configuration properties first.
+        String substValue = (configProps != null)
+            ? configProps.getProperty(variable, null)
+            : null;
+        if (substValue == null)
+        {
+            // Ignore unknown property values.
+            substValue = System.getProperty(variable, "");
+        }
+
+        // Remove the found variable from the cycle map, since
+        // it may appear more than once in the value and we don't
+        // want such situations to appear as a recursive reference.
+        cycleMap.remove(variable);
+
+        // Append the leading characters, the substituted value of
+        // the variable, and the trailing characters to get the new
+        // value.
+        val = val.substring(0, startDelim)
+            + substValue
+            + val.substring(stopDelim + DELIM_STOP.length(), val.length());
+
+        // Now perform substitution again, since there could still
+        // be substitutions to make.
+        val = substVars(val, currentKey, cycleMap, configProps);
+
+        // Return the value.
+        return val;
     }
 }
\ No newline at end of file
diff --git a/org.apache.felix.main/src/main/resources/config.properties b/org.apache.felix.main/src/main/resources/config.properties
index e28d343..a7468f3 100644
--- a/org.apache.felix.main/src/main/resources/config.properties
+++ b/org.apache.felix.main/src/main/resources/config.properties
@@ -5,18 +5,8 @@
  org.osgi.service.packageadmin; version=1.2.0, \
  org.osgi.service.startlevel; version=1.0.0, \
  org.osgi.service.url; version=1.0.0, \
- javax.swing; \
- javax.swing.plaf; \
- javax.swing.event; \
- javax.swing.table; \
- javax.swing.border; \
- javax.swing.tree; \
- javax.swing.text; \
- version=1.4, \
- org.w3c.dom, \
- org.xml.sax, \
- javax.xml.parsers, \
- javax.imageio
+ ${jre-${java.specification.version}}
+
 #org.osgi.framework.bootdelegation=sun.*,com.sun.*
 #felix.cache.profile=foo
 felix.auto.start.1= \
@@ -33,3 +23,153 @@
 org.osgi.service.http.port=8080
 obr.shell.telnet=on
 #obr.repository.url=http://bundles.osgi.org/obr/browse?_xml=1&cmd=repository
+
+
+#
+# Java platform package export properties.
+#
+jre-1.3= \
+ javax.swing; \
+ javax.swing.plaf; \
+ javax.swing.event; \
+ javax.swing.table; \
+ javax.swing.border; \
+ javax.swing.tree; \
+ javax.swing.text; \
+ version="1.3.0"
+
+jre-1.4= \
+ javax.swing; \
+ javax.swing.plaf; \
+ javax.swing.event; \
+ javax.swing.table; \
+ javax.swing.border; \
+ javax.swing.tree; \
+ javax.swing.text; \
+ version="1.4.0"
+
+jre-1.5= \
+  javax.accessibility; \
+  javax.activity; \
+  javax.imageio; \
+  javax.imageio.event; \
+  javax.imageio.metadata; \
+  javax.imageio.plugins.bmp; \
+  javax.imageio.plugins.jpeg; \
+  javax.imageio.spi; \
+  javax.imageio.stream; \
+  javax.management; \
+  javax.management.loading; \
+  javax.management.modelmbean; \
+  javax.management.monitor; \
+  javax.management.openmbean; \
+  javax.management.relation; \
+  javax.management.remote; \
+  javax.management.remote.rmi; \
+  javax.management.timer; \
+  javax.naming; \
+  javax.naming.directory; \
+  javax.naming.event; \
+  javax.naming.ldap; \
+  javax.naming.spi; \
+  javax.print; \
+  javax.print.attribute; \
+  javax.print.attribute.standard; \
+  javax.print.event; \
+  javax.rmi; \
+  javax.rmi.CORBA; \
+  javax.rmi.ssl; \
+  javax.security.auth; \
+  javax.security.auth.callback; \
+  javax.security.auth.kerberos; \
+  javax.security.auth.login; \
+  javax.security.auth.spi; \
+  javax.security.auth.x500; \
+  javax.security.sasl; \
+  javax.sound.midi; \
+  javax.sound.midi.spi; \
+  javax.sound.sampled; \
+  javax.sound.sampled.spi; \
+  javax.sql; \
+  javax.sql.rowset; \
+  javax.sql.rowset.serial; \
+  javax.sql.rowset.spi; \
+  javax.swing; \
+  javax.swing.border; \
+  javax.swing.colorchooser; \
+  javax.swing.event; \
+  javax.swing.filechooser; \
+  javax.swing.plaf; \
+  javax.swing.plaf.basic; \
+  javax.swing.plaf.basic.icons; \
+  javax.swing.plaf.metal; \
+  javax.swing.plaf.metal.icons; \
+  javax.swing.plaf.metal.icons.ocean; \
+  javax.swing.plaf.metal.sounds; \
+  javax.swing.plaf.multi; \
+  javax.swing.plaf.synth; \
+  javax.swing.table; \
+  javax.swing.text; \
+  javax.swing.text.html; \
+  javax.swing.text.html.icons; \
+  javax.swing.text.html.parser; \
+  javax.swing.text.rtf; \
+  javax.swing.text.rtf.charsets; \
+  javax.swing.tree; \
+  javax.swing.undo; \
+  javax.transaction; \
+  javax.transaction.xa; \
+  javax.xml; \
+  javax.xml.datatype; \
+  javax.xml.namespace; \
+  javax.xml.parsers; \
+  javax.xml.transform; \
+  javax.xml.transform.dom; \
+  javax.xml.transform.sax; \
+  javax.xml.transform.stream; \
+  javax.xml.validation; \
+  javax.xml.xpath; \
+  org.ietf.jgss; \
+  org.omg.CORBA; \
+  org.omg.CORBA.DynAnyPackage; \
+  org.omg.CORBA.ORBPackage; \
+  org.omg.CORBA.TypeCodePackage; \
+  org.omg.CORBA.portable; \
+  org.omg.CORBA_2_3; \
+  org.omg.CORBA_2_3.portable; \
+  org.omg.CosNaming; \
+  org.omg.CosNaming.NamingContextExtPackage; \
+  org.omg.CosNaming.NamingContextPackage; \
+  org.omg.Dynamic; \
+  org.omg.DynamicAny; \
+  org.omg.DynamicAny.DynAnyFactoryPackage; \
+  org.omg.DynamicAny.DynAnyPackage; \
+  org.omg.IOP; \
+  org.omg.IOP.CodecFactoryPackage; \
+  org.omg.IOP.CodecPackage; \
+  org.omg.Messaging; \
+  org.omg.PortableInterceptor; \
+  org.omg.PortableInterceptor.ORBInitInfoPackage; \
+  org.omg.PortableServer; \
+  org.omg.PortableServer.CurrentPackage; \
+  org.omg.PortableServer.POAManagerPackage; \
+  org.omg.PortableServer.POAPackage; \
+  org.omg.PortableServer.ServantLocatorPackage; \
+  org.omg.PortableServer.portable; \
+  org.omg.SendingContext; \
+  org.omg.stub.java.rmi; \
+  org.omg.stub.javax.management.remote.rmi; \
+  org.w3c.dom; \
+  org.w3c.dom.bootstrap; \
+  org.w3c.dom.css; \
+  org.w3c.dom.events; \
+  org.w3c.dom.html; \
+  org.w3c.dom.ls; \
+  org.w3c.dom.ranges; \
+  org.w3c.dom.stylesheets; \
+  org.w3c.dom.traversal; \
+  org.w3c.dom.views; \
+  org.xml.sax; \
+  org.xml.sax.ext; \
+  org.xml.sax.helpers; version="1.5.0"
+