Please add a new API getPublicIDs() to org.apache.xml.resolver.Catalog.java. An implementation may look like this: /** * Return all registered public IDs. */ public Iterator getPublicIDs() { Vector v = new Vector(); Enumeration enumeration = catalogEntries.elements(); while (enumeration.hasMoreElements()) { CatalogEntry e = (CatalogEntry) enumeration.nextElement(); if (e.getEntryType() == PUBLIC) { v.add(e.getEntryArg(0)); } } return v.iterator(); }