How to reload ResourceBundle (not from cache)??

Question

Does anyone know how to get a "fresh" ResourceBundle instead of the cached version?? I have read some solution (as described below that clears the sun.misc.SoftCache) which is working, but not a good coding practice.
Class klass = ResourceBundle.getBundle("resources.framework").getClass().getSuperclass();
Field field = klass.getDeclaredField("cacheList");
field.setAccessible(true);
sun.misc.SoftCache cache = (sun.misc.SoftCache)field.get(null);
cache.clear();
It is recommended by Sun NOT TO USE the sun.* package in the application codes because it is not supported by all other vendors and might not even be supported in the future relase of JDK. Does anyone know whetehr latest (e.g.,JDK 1.4) has changed the implementation to use standard pacakges or any other ways to not use the cached version, but load a fresh ResourceBundle from properties file??
Thanks for your help.
Frank Wang

Answer 1

Here you have a ReloadablePropertyResourceBundle that uses the cache if the file has not been changed. Other case, reload the properties file.
import java.util.ResourceBundle;
import java.util.PropertyResourceBundle;
import java.util.Locale;
import java.util.Vector;
import java.io.InputStream;
import java.util.Enumeration;
import java.lang.ref.SoftReference;
import java.util.MissingResourceException;
import java.net.URL;
import java.net.URLConnection;
import java.io.IOException;
import java.io.File;
public class ReloadablePropertyResourceBundle extends PropertyResourceBundle{
private static final String FILE_SUFIX = ".properties";
     private static sun.misc.SoftCache cacheList = new sun.misc.SoftCache();
     private static final AGResourceCacheKey cacheKey = new AGResourceCacheKey();
     private static class AGResourceCacheKey implements Cloneable {
          private SoftReference loaderRef;
          private String searchName;
          private int hashCodeCache;
          public boolean equals(Object other) {
               if (this == other) {
                    return true;
     if (null == other) {
                    return false;
     if (!(other instanceof AGResourceCacheKey)) {
                    return false;
     AGResourceCacheKey otherEntry = (AGResourceCacheKey)other;
               boolean result = hashCodeCache == otherEntry.hashCodeCache;
               if (result) {
                    //are the names the same
                    result = searchName.equals(otherEntry.searchName);
                    if (result) {
                         final boolean hasLoaderRef = loaderRef != null;
                         //are refs (both non-null) or (both null)
                         result = (hasLoaderRef && (otherEntry.loaderRef != null)) || (loaderRef == otherEntry.loaderRef);
                         //if both non-null, check that they reference the same loader
                         if (result && hasLoaderRef) {
                              result = loaderRef.get() == otherEntry.loaderRef.get();
               return result;
     public int hashCode() {
          return hashCodeCache;
          public Object clone() {
               try {
                    return super.clone();
               } catch (CloneNotSupportedException e) {
                    throw new InternalError();
          public void setKeyValues(ClassLoader loader, String searchName) {
               this.searchName = searchName;
               hashCodeCache = searchName.hashCode();
               if (loader == null) {
                    this.loaderRef = null;
               } else {
                    loaderRef = new SoftReference(loader);
                    hashCodeCache ^= loader.hashCode();
     private static final Object NOLOADER_NOTFOUND = new Integer(-1);
     private long lastModified = 0;
     private java.lang.String fileName = "";
public ReloadablePropertyResourceBundle(java.io.InputStream stream) throws java.io.IOException {
     super(stream);
public ReloadablePropertyResourceBundle(java.io.InputStream stream, String fileName, long lastModified) throws java.io.IOException {
     super(stream);
     this.fileName = fileName;
     this.lastModified = lastModified;
private static ClassLoader getLoader() {
     Class[] stack = new SecurityManager() {  
                    public Class[] getClassContext() {     
                              return super.getClassContext();
                    .getClassContext();          
     /* Magic number 2 identifies our caller's caller */
     Class c = stack[2];
     ClassLoader cl = (c == null) ? null : c.getClassLoader();
     if (cl == null) {
          cl = ClassLoader.getSystemClassLoader();
     return cl;
public static ResourceBundle getResourceBundle(String baseName) throws MissingResourceException {
     return getResourceBundle(baseName, Locale.getDefault());     
public static ResourceBundle getResourceBundle(String baseName, Locale locale) throws MissingResourceException {
     return getResourceBundle(baseName, locale, getLoader());     
public static ResourceBundle getResourceBundle(String baseName, Locale locale, ClassLoader loader) throws MissingResourceException {
     StringBuffer localeName = new StringBuffer("_").append(locale.toString());
     if (locale.toString().equals(""))
          localeName.setLength(0);
     ResourceBundle lookup = searchBundle(baseName, localeName, loader, false);
     if(lookup == null)
          localeName.setLength(0);
          localeName.append("_").append( Locale.getDefault().toString() );
          lookup = searchBundle(baseName, localeName, loader, true);
          if( lookup == null )
               throw new MissingResourceException("Can't find resource for base name "
                                                       + baseName + ", locale " + locale,
                                                       baseName + "_" + locale,"");
     // No parents
     return lookup;
private static URL getUrl(final String name, final ClassLoader loader) {
URL url = (URL)java.security.AccessController.doPrivileged (new java.security.PrivilegedAction() {
          public Object run()
                    if (loader != null)
                         return loader.getResource(name);
                    else
                    return ClassLoader.getSystemResource(name);
     return url;
private static ResourceBundle searchBundle(String baseName, StringBuffer localeName, final ClassLoader loader, boolean includeBase)
     String localeStr = localeName.toString();
     String baseFileName = baseName.replace('.', '/');
     Object lookup = null;
     String searchName;
     Vector cacheCandidates = new Vector();
     int lastUnderbar;
     InputStream stream = null;
     URL url = null;
     long lastDate = 0;
     URLConnection urlCon = null;
     Object NOTFOUND;
     if (loader == null)
          NOTFOUND = NOLOADER_NOTFOUND;
     else
          NOTFOUND = loader;
     searchLoop:
     while (true)
          searchName = baseName + localeStr;
          // look the property file
          searchName = baseFileName + localeStr + FILE_SUFIX;
     final String resName = searchName;
     // look in the cache
          synchronized (cacheList) {
               cacheKey.setKeyValues(loader, searchName);
               lookup = cacheList.get(cacheKey);
               //If the value == the class loader, this
               //signifies that a prior search failed
               if( lookup == NOTFOUND ) {
                    localeName.setLength(0);
                    break searchLoop;
               if( lookup != null )
                    // Creation date
                    if (lookup instanceof ReloadablePropertyResourceBundle)
                         String fileName = ((ReloadablePropertyResourceBundle)lookup).fileName;
                    url = getUrl(fileName, loader);
                    if (url != null)
                              lastDate = new File(url.getFile()).lastModified();
                         if ((url != null && ((ReloadablePropertyResourceBundle)lookup).lastModified == lastDate) || lastDate == 0)
                              localeName.setLength(0);
                              break searchLoop;
                         else
                              url = null;
                              lookup = null;
                              cacheList.remove(cacheKey);
                    else
                         localeName.setLength(0);
                         break searchLoop;
               cacheCandidates.addElement(cacheKey.clone() );
               cacheKey.setKeyValues(null, "");
          if (url == null)
          url = getUrl(resName, loader);
     if (url != null)
               try
                    urlCon = url.openConnection();
               catch (Exception e){}
     if (urlCon != null)
               try
               stream = urlCon.getInputStream();
                    lastDate = new File(url.getFile()).lastModified();
               catch (IOException e)
          if( stream != null )
               // make sure it is buffered
               stream = new java.io.BufferedInputStream(stream);
               try {
                    lookup = (Object)new ReloadablePropertyResourceBundle(stream, resName, lastDate);
                    break searchLoop;
               catch (Exception e) {
               finally {
                    try {
                         stream.close();
                    catch (Exception e) {
                         // to avoid propagating an IOException back into the caller
                         // (I'm assuming this is never going to happen, and if it does,
                         // I'm obeying the precedent of swallowing exceptions set by the
                         // existing code above)
          //Chop off the last part of the locale name string and try again.
          lastUnderbar = localeStr.lastIndexOf('_');
          if( ((lastUnderbar==0)&&(!includeBase)) || (lastUnderbar == -1) ) {
               break;
          localeStr = localeStr.substring(0,lastUnderbar);
          localeName.setLength(lastUnderbar);
     // If we searched all the way to the base, then we can add
     // the NOTFOUND result to the cache. Otherwise we can say
     // nothing.
     if (lookup == null && includeBase == true)
          lookup = NOTFOUND;
     if( lookup != null )
          synchronized (cacheList) {
               // Add a positive result to the cache. The result may include
               // NOTFOUND
               for( int i=0; i<cacheCandidates.size(); i++ ) {
                    cacheList.put(cacheCandidates.elementAt(i), lookup);
     if( (lookup == NOTFOUND) || (lookup == null) )
          return null;
     else
          return (ResourceBundle)lookup;