The catalog resolver handles the resolution of external * identifiers and URI references through XML catalogs. This * component supports XML catalogs defined by the * * OASIS XML Catalogs Specification. It encapsulates the * XML Commons resolver. * An instance of this class may be registered on the parser * as a SAX entity resolver or as an XNI entity resolver by setting * the property (http://apache.org/xml/properties/internal/entity-resolver).
* *It is intended that this class may be used standalone to perform * catalog resolution outside of a parsing context. It may be shared * between several parsers and the application.
* * @author Michael Glavassevich, IBM * * @version $Id: XMLCatalogResolver.java,v 1.2 2004/01/23 15:07:51 mrglavas Exp $ */ public class XMLCatalogResolver implements XMLEntityResolver, EntityResolver { /** Internal catalog manager for Apache catalogs. **/ private CatalogManager fResolverCatalogManager = null; /** Internal catalog structure. **/ private Catalog fCatalog = null; /** An array of catalog URIs. **/ private String [] fCatalogsList = null; /** * Indicates whether the list of catalogs has * changed since it was processed. */ private boolean fCatalogsChanged = true; /** Application specified prefer public setting. **/ private boolean fPreferPublic = true; /** * Indicates whether the application desires that * the parser or some other component performing catalog * resolution should use the literal system identifier * instead of the expanded system identifier. */ private boolean fUseLiteralSystemId = true; /** *Constructs a catalog resolver with a default configuration.
*/ public XMLCatalogResolver () { this(null, true); } /** *Constructs a catalog resolver with the given * list of entry files.
* * @param catalogs an ordered array list of absolute URIs */ public XMLCatalogResolver (String [] catalogs) { this(catalogs, true); } /** *Constructs a catalog resolver with the given * list of entry files and the preference for whether * system or public matches are preferred.
* * @param catalogs an ordered array list of absolute URIs * @param preferPublic the prefer public setting */ public XMLCatalogResolver (String [] catalogs, boolean preferPublic) { init(catalogs, preferPublic); } /** *Returns the initial list of catalog entry files.
* * @return the initial list of catalog entry files */ public final synchronized String [] getCatalogList () { return (fCatalogsList != null) ? (String[]) fCatalogsList.clone() : null; } /** *Sets the initial list of catalog entry files. * If there were any catalog mappings cached from * the previous list they will be replaced by catalog * mappings from the new list the next time the catalog * is queried.
* * @param catalogs an ordered array list of absolute URIs */ public final synchronized void setCatalogList (String [] catalogs) { fCatalogsChanged = true; fCatalogsList = (catalogs != null) ? (String[]) catalogs.clone() : null; } /** *Forces the cache of catalog mappings to be cleared.
*/ public final synchronized void clear () { fCatalog = null; } /** *Returns the preference for whether system or public
* matches are preferred. This is used in the absence
* of any occurence of the prefer attribute
* on the catalog entry of a catalog. If this
* property has not yet been explicitly set its value is
* true.
Sets the preference for whether system or public
* matches are preferred. This is used in the absence
* of any occurence of the prefer attribute
* on the catalog entry of a catalog.
Returns the preference for whether the literal system
* identifier should be used when resolving system
* identifiers when both it and the expanded system
* identifier are available. If this property has not yet
* been explicitly set its value is true.
Sets the preference for whether the literal system * identifier should be used when resolving system * identifiers when both it and the expanded system * identifier are available.
* *The literal system identifier is the URI as it was * provided before absolutization. It may be embedded within * an entity. It may be provided externally or it may be the * result of redirection. For example, redirection may * have come from the protocol level through HTTP or from * an application's entity resolver.
* *The expanded system identifier is an absolute URI * which is the result of resolving the literal system * identifier against a base URI.
* * @param useLiteralSystemId the preference for using * literal system identifers for catalog resolution */ public final void setUseLiteralSystemId (boolean useLiteralSystemId) { fUseLiteralSystemId = useLiteralSystemId; } /** *Resolves an external entity. If the entity cannot be
* resolved, this method should return null. This
* method returns an input source if an entry was found in the
* catalog for the given external identifier. It should be
* overrided if other behaviour is required.
null if none was supplied
* @param systemId the system identifier
*
* @throws SAXException any SAX exception, possibly wrapping another exception
* @throws IOException thrown if some i/o error occurs
*/
public InputSource resolveEntity(String publicId, String systemId)
throws SAXException, IOException {
String resolvedId = null;
if (publicId != null && systemId != null) {
resolvedId = resolvePublic(publicId, systemId);
}
else if (systemId != null) {
resolvedId = resolveSystem(systemId);
}
if (resolvedId != null) {
InputSource source = new InputSource(resolvedId);
source.setPublicId(publicId);
return source;
}
return null;
}
/**
* Resolves an external entity. If the entity cannot be
* resolved, this method should return null. This
* method only calls resolveIdentifier and returns
* an input source if an entry was found in the catalog. It
* should be overrided if other behaviour is required.
Resolves an identifier using the catalog. This method interprets that * the namespace of the identifier corresponds to uri entries in the catalog. * Where both a namespace and an external identifier exist, the namespace * takes precedence.
* * @param resourceIdentifier the identifier to resolve * * @throws XNIException thrown on general error * @throws IOException thrown if some i/o error occurs */ public String resolveIdentifier(XMLResourceIdentifier resourceIdentifier) throws IOException, XNIException { String resolvedId = null; // The namespace is useful for resolving namespace aware // grammars such as XML schema. Let it take precedence over // the external identifier if one exists. String namespace = resourceIdentifier.getNamespace(); if (namespace != null) { resolvedId = resolveURI(namespace); } // Resolve against an external identifier if one exists. This // is useful for resolving DTD external subsets and other // external entities. For XML schemas if there was no namespace // mapping we might be able to resolve a system identifier // specified as a location hint. if (resolvedId == null) { String publicId = resourceIdentifier.getPublicId(); String systemId = getUseLiteralSystemId() ? resourceIdentifier.getLiteralSystemId() : resourceIdentifier.getExpandedSystemId(); if (publicId != null && systemId != null) { resolvedId = resolvePublic(publicId, systemId); } else if (systemId != null) { resolvedId = resolveSystem(systemId); } } return resolvedId; } /** *Returns the URI mapping in the catalog for the given
* external identifier or null if no mapping
* exists. If the system identifier is an URN in the
* publicid namespace it is converted into
* a public identifier by URN "unwrapping" as specified
* in the XML Catalogs specification.
null if no mapping
* was found in the catalog
*
* @throws IOException if an i/o error occurred while reading
* the catalog
*/
public final synchronized String resolveSystem (String systemId)
throws IOException {
if (fCatalogsChanged) {
parseCatalogs();
fCatalogsChanged = false;
}
return (fCatalog != null)
? fCatalog.resolveSystem(systemId) : null;
}
/**
* Returns the URI mapping in the catalog for the given
* external identifier or null if no mapping
* exists. Public identifiers are normalized before
* comparison.
null if no mapping
* was found in the catalog
*
* @throws IOException if an i/o error occurred while reading
* the catalog
*/
public final synchronized String resolvePublic (String publicId, String systemId)
throws IOException {
if (fCatalogsChanged) {
parseCatalogs();
fCatalogsChanged = false;
}
return (fCatalog != null)
? fCatalog.resolvePublic(publicId, systemId) : null;
}
/**
* Returns the URI mapping in the catalog for the given URI
* reference or null if no mapping exists.
* URI comparison is case sensitive. If the URI reference
* is an URN in the publicid namespace
* it is converted into a public identifier by URN "unwrapping"
* as specified in the XML Catalogs specification and then
* resolution is performed following the semantics of
* external identifier resolution.
null if no mapping
* was found in the catalog
*
* @throws IOException if an i/o error occurred while reading
* the catalog
*/
public final synchronized String resolveURI (String uri)
throws IOException {
if (fCatalogsChanged) {
parseCatalogs();
fCatalogsChanged = false;
}
return (fCatalog != null)
? fCatalog.resolveURI(uri) : null;
}
/**
* Initialization. Create a CatalogManager and set all
* the properties upfront. This prevents JVM wide system properties
* or a property file somewhere in the environment from affecting
* the behaviour of this catalog resolver.
*/
private void init (String [] catalogs, boolean preferPublic) {
fCatalogsList = (catalogs != null) ? (String[]) catalogs.clone() : null;
fPreferPublic = preferPublic;
fResolverCatalogManager = new CatalogManager();
fResolverCatalogManager.setAllowOasisXMLCatalogPI(false);
fResolverCatalogManager.setCatalogClassName("org.apache.xml.resolver.Catalog");
fResolverCatalogManager.setCatalogFiles("");
fResolverCatalogManager.setIgnoreMissingProperties(true);
fResolverCatalogManager.setPreferPublic(fPreferPublic);
fResolverCatalogManager.setRelativeCatalogs(false);
fResolverCatalogManager.setUseStaticCatalog(false);
fResolverCatalogManager.setVerbosity(0);
}
/**
* Instruct the Catalog to parse each of the
* catalogs in the list. Only the first catalog will actually be
* parsed immediately. The others will be queued and read if
* they are needed later.
*/
private void parseCatalogs () throws IOException {
if (fCatalogsList != null) {
fCatalog = new Catalog(fResolverCatalogManager);
attachReaderToCatalog(fCatalog);
for (int i = 0; i < fCatalogsList.length; ++i) {
String catalog = fCatalogsList[i];
if (catalog != null && catalog.length() > 0) {
fCatalog.parseCatalog(catalog);
}
}
}
else {
fCatalog = null;
}
}
/**
* Attaches the reader to the catalog.
*/
private void attachReaderToCatalog (Catalog catalog) {
SAXParserFactory spf = new SAXParserFactoryImpl();
spf.setNamespaceAware(true);
spf.setValidating(false);
SAXCatalogReader saxReader = new SAXCatalogReader(spf);
saxReader.setCatalogParser(OASISXMLCatalogReader.namespaceName, "catalog",
"org.apache.xml.resolver.readers.OASISXMLCatalogReader");
catalog.addReader("application/xml", saxReader);
}
}