private ExternalizableMap loadMap(String extMapName, ClassLoader loader)
     throws FileNotFoundException {
   String first = null;
   String next = extMapName;
   List<String> urls = new ArrayList<String>();
   ExternalizableMap res = null;
   while (next != null) {
     // convert the plugin class name to an xml file name
     String mapFile = next.replace('.', '/') + MAP_SUFFIX;
     URL url = loader.getResource(mapFile);
     if (url != null && urls.contains(url.toString())) {
       throw new PluginException.InvalidDefinition("Plugin inheritance loop: " + next);
     }
     // load into map
     ExternalizableMap oneMap = new ExternalizableMap();
     oneMap.loadMapFromResource(mapFile, loader);
     urls.add(url.toString());
     // apply overrides one plugin at a time in inheritance chain
     processOverrides(oneMap);
     if (res == null) {
       res = oneMap;
     } else {
       for (Map.Entry ent : oneMap.entrySet()) {
         String key = (String) ent.getKey();
         Object val = ent.getValue();
         if (!res.containsKey(key)) {
           res.setMapElement(key, val);
         }
       }
     }
     if (oneMap.containsKey(KEY_PLUGIN_PARENT)) {
       next = oneMap.getString(KEY_PLUGIN_PARENT);
     } else {
       next = null;
     }
   }
   loadedFromUrls = urls;
   return res;
 }
 protected void initMimeMap() throws PluginException.InvalidDefinition {
   for (Iterator iter = definitionMap.entrySet().iterator(); iter.hasNext(); ) {
     Map.Entry ent = (Map.Entry) iter.next();
     String key = (String) ent.getKey();
     Object val = ent.getValue();
     if (key.endsWith(DefinableArchivalUnit.SUFFIX_LINK_EXTRACTOR_FACTORY)) {
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_LINK_EXTRACTOR_FACTORY);
       if (val instanceof String) {
         String factName = (String) val;
         log.debug(mime + " link extractor: " + factName);
         MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
         LinkExtractorFactory fact =
             (LinkExtractorFactory) newAuxClass(factName, LinkExtractorFactory.class);
         mti.setLinkExtractorFactory(fact);
       }
     } else if (key.endsWith(DefinableArchivalUnit.SUFFIX_CRAWL_FILTER_FACTORY)) {
       // XXX This clause must precede the one for SUFFIX_HASH_FILTER_FACTORY
       // XXX unless/until that key is changed to not be a terminal substring
       // XXX of this one
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_CRAWL_FILTER_FACTORY);
       if (val instanceof String) {
         String factName = (String) val;
         log.debug(mime + " crawl filter: " + factName);
         MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
         FilterFactory fact = (FilterFactory) newAuxClass(factName, FilterFactory.class);
         mti.setCrawlFilterFactory(fact);
       }
     } else if (key.endsWith(DefinableArchivalUnit.SUFFIX_HASH_FILTER_FACTORY)) {
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_HASH_FILTER_FACTORY);
       if (val instanceof String) {
         String factName = (String) val;
         log.debug(mime + " filter: " + factName);
         MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
         FilterFactory fact = (FilterFactory) newAuxClass(factName, FilterFactory.class);
         mti.setHashFilterFactory(fact);
       }
     } else if (key.endsWith(DefinableArchivalUnit.SUFFIX_FETCH_RATE_LIMIT)) {
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_FETCH_RATE_LIMIT);
       if (val instanceof String) {
         String rate = (String) val;
         log.debug(mime + " fetch rate: " + rate);
         MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
         RateLimiter limit = mti.getFetchRateLimiter();
         if (limit != null) {
           limit.setRate(rate);
         } else {
           mti.setFetchRateLimiter(new RateLimiter(rate));
         }
       }
     } else if (key.endsWith(DefinableArchivalUnit.SUFFIX_LINK_REWRITER_FACTORY)) {
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_LINK_REWRITER_FACTORY);
       String factName = (String) val;
       log.debug(mime + " link rewriter: " + factName);
       MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
       LinkRewriterFactory fact =
           (LinkRewriterFactory) newAuxClass(factName, LinkRewriterFactory.class);
       mti.setLinkRewriterFactory(fact);
     } else if (key.endsWith(DefinableArchivalUnit.SUFFIX_METADATA_EXTRACTOR_FACTORY_MAP)) {
       String mime = stripSuffix(key, DefinableArchivalUnit.SUFFIX_METADATA_EXTRACTOR_FACTORY_MAP);
       Map factNameMap = (Map) val;
       Map factClassMap = new HashMap();
       MimeTypeInfo.Mutable mti = mimeMap.modifyMimeTypeInfo(mime);
       for (Iterator it = factNameMap.keySet().iterator(); it.hasNext(); ) {
         String mdTypes = (String) it.next();
         String factName = (String) factNameMap.get(mdTypes);
         log.debug(mime + " (" + mdTypes + ") metadata extractor: " + factName);
         for (String mdType : (List<String>) StringUtil.breakAt(mdTypes, ";")) {
           setMdTypeFact(factClassMap, mdType, factName);
         }
       }
       mti.setFileMetadataExtractorFactoryMap(factClassMap);
     }
   }
 }