If a SAX application needs to implement customized handling * for external entities, it must implement this interface and * register an instance with the SAX driver using the * {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver} * method.
* *The XML reader will then allow the application to intercept any * external entities (including the external DTD subset and external * parameter entities, if any) before including them.
* *Many SAX applications will not need to implement this interface, * but it will be especially useful for applications that build * XML documents from databases or other specialised input sources, * or for applications that use URI types other than URLs.
* *The following resolver would provide the application * with a special character stream for the entity with the system * identifier "http://www.myhost.com/today":
* *
* import org.xml.sax.EntityResolver;
* import org.xml.sax.InputSource;
*
* public class MyResolver implements EntityResolver {
* public InputSource resolveEntity (String publicId, String systemId)
* {
* if (systemId.equals("http://www.myhost.com/today")) {
* // return a special input source
* MyReader reader = new MyReader();
* return new InputSource(reader);
* } else {
* // use the default behaviour
* return null;
* }
* }
* }
*
*
* The application can also use this interface to redirect system * identifiers to local URIs or to look up replacements in a catalog * (possibly by using the public identifier).
* * @since 1.4, SAX 1.0 * @author David Megginson * @see org.xml.sax.XMLReader#setEntityResolver * @see org.xml.sax.InputSource */ public interface EntityResolver { /** * Allow the application to resolve external entities. * *The parser will call this method before opening any external * entity except the top-level document entity. Such entities include * the external DTD subset and external parameter entities referenced * within the DTD (in either case, only if the parser reads external * parameter entities), and external general entities referenced * within the document element (if the parser reads external general * entities). The application may request that the parser locate * the entity itself, that it use an alternative URI, or that it * use data provided by the application (as a character or byte * input stream).
* *Application writers can use this method to redirect external * system identifiers to secure and/or local URIs, to look up * public identifiers in a catalogue, or to read an entity from a * database or other input source (including, for example, a dialog * box). Neither XML nor SAX specifies a preferred policy for using * public or system IDs to resolve resources. However, SAX specifies * how to interpret any InputSource returned by this method, and that * if none is returned, then the system ID will be dereferenced as * a URL.
* *If the system identifier is a URL, the SAX parser must * resolve it fully before reporting it to the application.
* * @param publicId The public identifier of the external entity * being referenced, or null if none was supplied. * @param systemId The system identifier of the external entity * being referenced. * @return An InputSource object describing the new input source, * or null to request that the parser open a regular * URI connection to the system identifier. * @throws org.xml.sax.SAXException Any SAX exception, possibly * wrapping another exception. * @throws java.io.IOException A Java-specific IO exception, * possibly the result of creating a new InputStream * or Reader for the InputSource. * @see org.xml.sax.InputSource */ public abstract InputSource resolveEntity (String publicId, String systemId) throws SAXException, IOException; } // end of EntityResolver.java