1 // SAX entity resolver. 2 // http://www.saxproject.org 3 // No warranty; no copyright -- use this as you will. 4 // $Id: EntityResolver.java,v 1.10 2002/01/30 21:13:44 dbrownell Exp $ 5 6 package org.xml.sax; 7 8 import java.io.IOException; 9 10 11 /** 12 * Basic interface for resolving entities. 13 * 14 * <blockquote> 15 * <em>This module, both source code and documentation, is in the 16 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em> 17 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a> 18 * for further information. 19 * </blockquote> 20 * 21 * <p>If a SAX application needs to implement customized handling 22 * for external entities, it must implement this interface and 23 * register an instance with the SAX driver using the 24 * {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver} 25 * method.</p> 26 * 27 * <p>The XML reader will then allow the application to intercept any 28 * external entities (including the external DTD subset and external 29 * parameter entities, if any) before including them.</p> 30 * 31 * <p>Many SAX applications will not need to implement this interface, 32 * but it will be especially useful for applications that build 33 * XML documents from databases or other specialised input sources, 34 * or for applications that use URI types other than URLs.</p> 35 * 36 * <p>The following resolver would provide the application 37 * with a special character stream for the entity with the system 38 * identifier "http://www.myhost.com/today":</p> 39 * 40 * <pre> 41 * import org.xml.sax.EntityResolver; 42 * import org.xml.sax.InputSource; 43 * 44 * public class MyResolver implements EntityResolver { 45 * public InputSource resolveEntity (String publicId, String systemId) 46 * { 47 * if (systemId.equals("http://www.myhost.com/today")) { 48 * // return a special input source 49 * MyReader reader = new MyReader(); 50 * return new InputSource(reader); 51 * } else { 52 * // use the default behaviour 53 * return null; 54 * } 55 * } 56 * } 57 * </pre> 58 * 59 * <p>The application can also use this interface to redirect system 60 * identifiers to local URIs or to look up replacements in a catalog 61 * (possibly by using the public identifier).</p> 62 * 63 * @since SAX 1.0 64 * @author David Megginson 65 * @version 2.0.1 (sax2r2) 66 * @see org.xml.sax.XMLReader#setEntityResolver 67 * @see org.xml.sax.InputSource 68 */ 69 public interface EntityResolver { 70 71 72 /** 73 * Allow the application to resolve external entities. 74 * 75 * <p>The parser will call this method before opening any external 76 * entity except the top-level document entity. Such entities include 77 * the external DTD subset and external parameter entities referenced 78 * within the DTD (in either case, only if the parser reads external 79 * parameter entities), and external general entities referenced 80 * within the document element (if the parser reads external general 81 * entities). The application may request that the parser locate 82 * the entity itself, that it use an alternative URI, or that it 83 * use data provided by the application (as a character or byte 84 * input stream).</p> 85 * 86 * <p>Application writers can use this method to redirect external 87 * system identifiers to secure and/or local URIs, to look up 88 * public identifiers in a catalogue, or to read an entity from a 89 * database or other input source (including, for example, a dialog 90 * box). Neither XML nor SAX specifies a preferred policy for using 91 * public or system IDs to resolve resources. However, SAX specifies 92 * how to interpret any InputSource returned by this method, and that 93 * if none is returned, then the system ID will be dereferenced as 94 * a URL. </p> 95 * 96 * <p>If the system identifier is a URL, the SAX parser must 97 * resolve it fully before reporting it to the application.</p> 98 * 99 * @param publicId The public identifier of the external entity 100 * being referenced, or null if none was supplied. 101 * @param systemId The system identifier of the external entity 102 * being referenced. 103 * @return An InputSource object describing the new input source, 104 * or null to request that the parser open a regular 105 * URI connection to the system identifier. 106 * @exception org.xml.sax.SAXException Any SAX exception, possibly 107 * wrapping another exception. 108 * @exception java.io.IOException A Java-specific IO exception, 109 * possibly the result of creating a new InputStream 110 * or Reader for the InputSource. 111 * @see org.xml.sax.InputSource 112 */ 113 public abstract InputSource resolveEntity (String publicId, 114 String systemId) 115 throws SAXException, IOException; 116 117 } 118 119 // end of EntityResolver.java 120
