1 /* 2 * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package org.xml.sax; 27 28 import java.io.IOException; 29 30 31 /** 32 * Basic interface for resolving entities. 33 * 34 * <p>If a SAX application needs to implement customized handling 35 * for external entities, it must implement this interface and 36 * register an instance with the SAX driver using the 37 * {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver} 38 * method.</p> 39 * 40 * <p>The XML reader will then allow the application to intercept any 41 * external entities (including the external DTD subset and external 42 * parameter entities, if any) before including them.</p> 43 * 44 * <p>Many SAX applications will not need to implement this interface, 45 * but it will be especially useful for applications that build 46 * XML documents from databases or other specialised input sources, 47 * or for applications that use URI types other than URLs.</p> 48 * 49 * <p>The following resolver would provide the application 50 * with a special character stream for the entity with the system 51 * identifier "http://www.myhost.com/today":</p> 52 * 53 * <pre> 54 * import org.xml.sax.EntityResolver; 55 * import org.xml.sax.InputSource; 56 * 57 * public class MyResolver implements EntityResolver { 58 * public InputSource resolveEntity (String publicId, String systemId) 59 * { 60 * if (systemId.equals("http://www.myhost.com/today")) { 61 * // return a special input source 62 * MyReader reader = new MyReader(); 63 * return new InputSource(reader); 64 * } else { 65 * // use the default behaviour 66 * return null; 67 * } 68 * } 69 * } 70 * </pre> 71 * 72 * <p>The application can also use this interface to redirect system 73 * identifiers to local URIs or to look up replacements in a catalog 74 * (possibly by using the public identifier).</p> 75 * 76 * @since 1.4, SAX 1.0 77 * @author David Megginson 78 * @see org.xml.sax.XMLReader#setEntityResolver 79 * @see org.xml.sax.InputSource 80 */ 81 public interface EntityResolver { 82 83 84 /** 85 * Allow the application to resolve external entities. 86 * 87 * <p>The parser will call this method before opening any external 88 * entity except the top-level document entity. Such entities include 89 * the external DTD subset and external parameter entities referenced 90 * within the DTD (in either case, only if the parser reads external 91 * parameter entities), and external general entities referenced 92 * within the document element (if the parser reads external general 93 * entities). The application may request that the parser locate 94 * the entity itself, that it use an alternative URI, or that it 95 * use data provided by the application (as a character or byte 96 * input stream).</p> 97 * 98 * <p>Application writers can use this method to redirect external 99 * system identifiers to secure and/or local URIs, to look up 100 * public identifiers in a catalogue, or to read an entity from a 101 * database or other input source (including, for example, a dialog 102 * box). Neither XML nor SAX specifies a preferred policy for using 103 * public or system IDs to resolve resources. However, SAX specifies 104 * how to interpret any InputSource returned by this method, and that 105 * if none is returned, then the system ID will be dereferenced as 106 * a URL. </p> 107 * 108 * <p>If the system identifier is a URL, the SAX parser must 109 * resolve it fully before reporting it to the application.</p> 110 * 111 * @param publicId The public identifier of the external entity 112 * being referenced, or null if none was supplied. 113 * @param systemId The system identifier of the external entity 114 * being referenced. 115 * @return An InputSource object describing the new input source, 116 * or null to request that the parser open a regular 117 * URI connection to the system identifier. 118 * @exception org.xml.sax.SAXException Any SAX exception, possibly 119 * wrapping another exception. 120 * @exception java.io.IOException A Java-specific IO exception, 121 * possibly the result of creating a new InputStream 122 * or Reader for the InputSource. 123 * @see org.xml.sax.InputSource 124 */ 125 public abstract InputSource resolveEntity (String publicId, 126 String systemId) 127 throws SAXException, IOException; 128 129 } 130 131 // end of EntityResolver.java