FrontendDefaultHandler


1   /* ========================================================================
2    * JCommon : a free general purpose class library for the Java(tm) platform
3    * ========================================================================
4    *
5    * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
6    * 
7    * Project Info:  http://www.jfree.org/jcommon/index.html
8    *
9    * This library is free software; you can redistribute it and/or modify it 
10   * under the terms of the GNU Lesser General Public License as published by 
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12   * (at your option) any later version.
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14   * This library is distributed in the hope that it will be useful, but 
15   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
16   * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
17   * License for more details.
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23   *
24   * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
25   * in the United States and other countries.]
26   *
27   * ------------
28   * FrontendDefaultHandler.java
29   * ------------
30   * (C) Copyright 2002-2005, by Object Refinery Limited.
31   *
32   * Original Author:  David Gilbert (for Object Refinery Limited);
33   * Contributor(s):   -;
34   *
35   * $Id: FrontendDefaultHandler.java,v 1.8 2006/11/20 21:36:30 taqua Exp $
36   *
37   * Changes
38   * -------
39   * 02-Feb-2005 : Initial version.
40   *
41   */
42  package org.jfree.xml;
43  
44  import java.net.MalformedURLException  ;
45  import java.net.URL  ;
46  import java.util.Iterator  ;
47  import java.util.Enumeration  ;
48  
49  import org.jfree.util.Configuration;
50  import org.jfree.util.DefaultConfiguration;
51  import org.xml.sax.Locator  ;
52  import org.xml.sax.SAXException  ;
53  import org.xml.sax.helpers.DefaultHandler  ;
54  
55  /**
56   * The frontenddefault handler connects the SAX-backend with the handler implementations.
57   * It must be the base class for all parser implementations used by the ParserFrontEnd.
58   *
59   * @author Thomas Morgner
60   */
61  public abstract class FrontendDefaultHandler extends DefaultHandler   implements Configuration {
62      /**
63       * A key for the content base.
64       */
65      public static final String   CONTENTBASE_KEY = "content-base";
66  
67      /**
68       * Storage for the parser configuration.
69       */
70      private DefaultConfiguration parserConfiguration;
71  
72      /**
73       * The DocumentLocator can be used to resolve the current parse position.
74       */
75      private Locator   locator;
76  
77      /**
78       * The current comment handler used to receive xml comments.
79       */
80      private final CommentHandler commentHandler;
81  
82      /**
83       * Default constructor.
84       */
85      protected FrontendDefaultHandler() {
86          this.parserConfiguration = new DefaultConfiguration();
87          this.commentHandler = new CommentHandler();
88      }
89  
90      /**
91       * Returns the comment handler that is used to collect comments.
92       *
93       * @return the comment handler.
94       */
95      public CommentHandler getCommentHandler() {
96          return this.commentHandler;
97      }
98  
99      /**
100      * Receive an object for locating the origin of SAX document events.
101      * <p/>
102      * The locator allows the application to determine the end position of
103      * any document-related event, even if the parser is not reporting an
104      * error. Typically, the application will use this information for
105      * reporting its own errors (such as character content that does not
106      * match an application's business rules). The information returned by
107      * the locator is probably not sufficient for use with a search engine.
108      *
109      * @param locator the locator.
110      */
111     public void setDocumentLocator(final Locator   locator) {
112         this.locator = locator;
113     }
114 
115     /**
116      * Returns the current locator.
117      *
118      * @return the locator.
119      */
120     public Locator   getLocator() {
121         return this.locator;
122     }
123 
124     /**
125      * Returns the configuration property with the specified key.
126      *
127      * @param key the property key.
128      * @return the property value.
129      */
130     public String   getConfigProperty(final String   key) {
131         return getConfigProperty(key, null);
132     }
133 
134     /**
135      * Returns the configuration property with the specified key (or the specified default value
136      * if there is no such property).
137      * <p/>
138      * If the property is not defined in this configuration, the code will lookup the property in
139      * the parent configuration.
140      *
141      * @param key          the property key.
142      * @param defaultValue the default value.
143      * @return the property value.
144      */
145     public String   getConfigProperty(final String   key, final String   defaultValue) {
146         return this.parserConfiguration.getConfigProperty(key, defaultValue);
147     }
148 
149     /**
150      * Sets a parser configuration value.
151      *
152      * @param key   the key.
153      * @param value the value.
154      */
155     public void setConfigProperty(final String   key, final String   value) {
156         if (value == null) {
157             this.parserConfiguration.remove(key);
158         }
159         else {
160             this.parserConfiguration.setProperty(key, value);
161         }
162     }
163 
164     public Enumeration   getConfigProperties()
165     {
166       return parserConfiguration.getConfigProperties();
167     }
168 
169   /**
170      * Returns a new instance of the parser.
171      *
172      * @return a new instance of the parser.
173      */
174     public abstract FrontendDefaultHandler newInstance();
175 
176     /**
177      * Returns all keys with the given prefix.
178      *
179      * @param prefix the prefix
180      * @return the iterator containing all keys with that prefix
181      */
182     public Iterator   findPropertyKeys(final String   prefix) {
183         return this.parserConfiguration.findPropertyKeys(prefix);
184     }
185 
186     /**
187      * Returns the parse result. This method is called at the end of the
188      * parsing process and expects the generated object.
189      *
190      * @return the object.
191      * @throws SAXException if something went wrong.
192      */
193     public abstract Object   getResult() throws SAXException  ;
194 
195     /**
196      * Gets the ContentBase used to resolve relative URLs.
197      *
198      * @return the current contentbase, or null if no contentBase is set.
199      */
200     public URL   getContentBase() {
201         final String   contentBase = getConfigProperty(Parser.CONTENTBASE_KEY);
202         if (contentBase == null) {
203             return null;
204         }
205         try {
206             return new URL  (contentBase);
207         }
208         catch (MalformedURLException   mfe) {
209             throw new IllegalStateException  ("Content Base is illegal." + contentBase);
210         }
211     }
212 
213     public Object   clone () throws CloneNotSupportedException  
214     {
215       final FrontendDefaultHandler o = (FrontendDefaultHandler) super.clone();
216       o.parserConfiguration = (DefaultConfiguration) parserConfiguration.clone();
217       return o;
218     }
219 }
220
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