001: /*
002: * ====================================================================
003: * JAFFA - Java Application Framework For All
004: *
005: * Copyright (C) 2002 JAFFA Development Group
006: *
007: * This library is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU Lesser General Public
009: * License as published by the Free Software Foundation; either
010: * version 2.1 of the License, or (at your option) any later version.
011: *
012: * This library is distributed in the hope that it will be useful,
013: * but WITHOUT ANY WARRANTY; without even the implied warranty of
014: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015: * Lesser General Public License for more details.
016: *
017: * You should have received a copy of the GNU Lesser General Public
018: * License along with this library; if not, write to the Free Software
019: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
020: *
021: * Redistribution and use of this software and associated documentation ("Software"),
022: * with or without modification, are permitted provided that the following conditions are met:
023: * 1. Redistributions of source code must retain copyright statements and notices.
024: * Redistributions must also contain a copy of this document.
025: * 2. Redistributions in binary form must reproduce the above copyright notice,
026: * this list of conditions and the following disclaimer in the documentation
027: * and/or other materials provided with the distribution.
028: * 3. The name "JAFFA" must not be used to endorse or promote products derived from
029: * this Software without prior written permission. For written permission,
030: * please contact mail to: jaffagroup@yahoo.com.
031: * 4. Products derived from this Software may not be called "JAFFA" nor may "JAFFA"
032: * appear in their names without prior written permission.
033: * 5. Due credit should be given to the JAFFA Project (http://jaffa.sourceforge.net).
034: *
035: * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
036: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038: * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
039: * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
040: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
041: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
042: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
043: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
044: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
045: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
046: * SUCH DAMAGE.
047: * ====================================================================
048: */
049:
050: package org.jaffa.rules.metadata;
051:
052: import java.util.*;
053: import java.net.URL;
054: import org.jaffa.cache.CacheManager;
055: import org.jaffa.cache.ICache;
056: import org.jaffa.util.URLHelper;
057: import org.jaffa.security.VariationContext;
058: import org.jaffa.config.Config;
059: import org.jaffa.datatypes.Parser;
060: import org.jaffa.util.DefaultEntityResolver;
061: import org.jaffa.util.DefaultErrorHandler;
062:
063: import org.xml.sax.helpers.XMLReaderFactory;
064: import org.xml.sax.XMLReader;
065: import org.xml.sax.InputSource;
066: import org.xml.sax.helpers.DefaultHandler;
067: import org.xml.sax.Attributes;
068:
069: import org.xml.sax.SAXException;
070: import java.io.IOException;
071: import java.io.FileNotFoundException;
072:
073: /** This parses the Rules config file and creates instances of the ClassMetaData class. These instances are cached.
074: */
075: public class RulesMetaDataService {
076:
077: public static final String VARIATION_FILE_SUFFIX = "-rules.xml";
078: private static final String PARSER_NAME = "org.apache.xerces.parsers.SAXParser";
079: private static final String DEFAULT_XML_FILE = "classpath:///resources/core-rules.xml";
080: private static final String SUCCESS_MESSAGE = RulesMetaDataService.class
081: .getName();
082: private static Map c_caches = new HashMap();
083:
084: /** Returns an instance of ClassMetaData for the given name. A null will be returned in case no definition is found in the Rules Config file.
085: * @param className The class for which the XML will be parsed.
086: * @param variation This will determine the Rules config file to be parsed. If a null is passed, then the core file will be parsed.
087: * @return an instance of ClassMetaData.
088: * @throws SAXException If any exception is thrown while parsing the XML file.
089: * @throws IOException If any I/O error occurs in reading the XML file. Note: A FileNotFoundException will be thrown, in case the file is not found.
090: */
091: public static ClassMetaData getClassMetaData(String className,
092: String variation) throws SAXException, IOException {
093: if (variation == null)
094: variation = VariationContext.DEFAULT_VARIATION;
095:
096: // Get the appropriate cache
097: ICache cache = (ICache) c_caches.get(variation);
098: if (cache == null) {
099: synchronized (c_caches) {
100: // try again
101: cache = (ICache) c_caches.get(variation);
102: if (cache == null) {
103: cache = CacheManager
104: .getCache(RulesMetaDataService.class
105: .getName()
106: + '-' + variation);
107: c_caches.put(variation, cache);
108: }
109: }
110: }
111:
112: // Now check the cache
113: if (!cache.containsKey(className))
114: find(className, cache, variation);
115: return (ClassMetaData) cache.get(className);
116: }
117:
118: /** Parse the rules-xml file for the given named className.
119: */
120: private static void find(String className, ICache cache,
121: String variation) throws SAXException, IOException {
122: synchronized (cache) {
123: if (cache.containsKey(className))
124: return;
125:
126: CustomHandler handler = new CustomHandler(className);
127: try {
128: String xmlFile;
129: if (VariationContext.DEFAULT_VARIATION
130: .equals(variation))
131: xmlFile = (String) Config.getProperty(
132: Config.PROP_RULES_ENGINE_CORE_RULES_URL,
133: DEFAULT_XML_FILE);
134: else {
135: String variationRulesDirectory = (String) Config
136: .getProperty(
137: Config.PROP_RULES_ENGINE_VARIATIONS_DIR,
138: null);
139: if (variationRulesDirectory == null
140: || variationRulesDirectory.length() == 0) {
141: // No directory specified. Hence no variations exist. Just return.
142: return;
143: } else {
144: xmlFile = variationRulesDirectory + '/'
145: + variation + VARIATION_FILE_SUFFIX;
146: }
147: }
148: URL url = URLHelper.newExtendedURL(xmlFile);
149: if (url == null)
150: throw new FileNotFoundException("File not found - "
151: + xmlFile);
152:
153: XMLReader reader = XMLReaderFactory
154: .createXMLReader(PARSER_NAME);
155: reader.setContentHandler(handler);
156: reader.setEntityResolver(new DefaultEntityResolver());
157: reader.setErrorHandler(new DefaultErrorHandler());
158: reader.parse(new InputSource(url.openStream()));
159: cache.put(className, handler.getClassMetaData());
160: } catch (SAXException e) {
161: // Its alrite if the SUCCESS_MESSAGE is returned
162: if (SUCCESS_MESSAGE.equals(e.getMessage()))
163: cache.put(className, handler.getClassMetaData());
164: else
165: throw e;
166: } catch (IOException e) {
167: throw e;
168: }
169: }
170: }
171:
172: /** This will handle the SAX events raised while parsing the rules xml file. */
173: private static class CustomHandler extends DefaultHandler {
174:
175: private static final String DOMAIN = "domain";
176: private static final String DTO = "dto";
177: private static final String CLASS = "class";
178: private static final String FIELD = "field";
179: private static final String NAME = "name";
180: private static final String OVERRIDES_DEFAULT = "overridesDefault";
181: private static final String EXTENDS_CLASS = "extendsClass";
182: private static final String EXTENDS_FIELD = "extendsField";
183:
184: private String m_className = null;
185: private ClassMetaData m_classMetaData = null;
186: private FieldMetaData m_fieldMetaData = null;
187:
188: /** Create an instance.
189: */
190: private CustomHandler(String className) {
191: m_className = className;
192: }
193:
194: /** Returns the ClassMetaData for the given name. A null may be returned, if no matching definition was found.
195: */
196: private ClassMetaData getClassMetaData() {
197: return m_classMetaData;
198: }
199:
200: /** Receive notification of the start of an element.
201: * @param uri The uri.
202: * @param sName The local name (without prefix), or the empty string if Namespace processing is not being performed.
203: * @param qName The qualified name (with prefix), or the empty string if qualified names are not available.
204: * @param atts The specified or defaulted attributes
205: */
206: public void startElement(String uri, String sName,
207: String qName, Attributes atts) {
208: if (m_classMetaData == null) {
209: if (sName.equals(DOMAIN) || sName.equals(DTO)) {
210: if (m_className.equals(atts.getValue(CLASS))) {
211: m_classMetaData = new ClassMetaData();
212: m_classMetaData.setClassName(m_className);
213: }
214: }
215: } else {
216: if (sName.equals(FIELD)) {
217: m_fieldMetaData = new FieldMetaData();
218: m_fieldMetaData.setName(atts.getValue(NAME));
219: m_fieldMetaData.setOverridesDefault(Parser
220: .parseBoolean(
221: atts.getValue(OVERRIDES_DEFAULT))
222: .booleanValue());
223: m_fieldMetaData.setExtendsClass(atts
224: .getValue(EXTENDS_CLASS));
225: m_fieldMetaData.setExtendsField(atts
226: .getValue(EXTENDS_FIELD));
227: m_classMetaData.addField(m_fieldMetaData);
228: } else if (m_fieldMetaData != null) {
229: RuleMetaData ruleMetaData = new RuleMetaData();
230: ruleMetaData.setName(sName);
231: for (int i = 0; i < atts.getLength(); i++) {
232: String name = atts.getQName(i);
233: ruleMetaData.addParameter(name, atts
234: .getValue(name));
235: }
236: m_fieldMetaData.addRule(ruleMetaData);
237: }
238: }
239: }
240:
241: /** Receive notification of the end of an element.
242: * @param uri The uri.
243: * @param sName The local name (without prefix), or the empty string if Namespace processing is not being performed.
244: * @param qName The qualified name (with prefix), or the empty string if qualified names are not available.
245: * @throws SAXException Any SAX exception, possibly wrapping another exception. NOTE: This exception will also be thrown after the named validator is found, so as to terminate any further parsing.
246: */
247: public void endElement(String uri, String sName, String qName)
248: throws SAXException {
249: if (m_classMetaData != null) {
250: if (sName.equals(DOMAIN) || sName.equals(DTO)) {
251: // the classMetaData has been found. End the parsing.
252: throw new SAXException(SUCCESS_MESSAGE);
253: }
254: }
255: }
256: }
257:
258: public static void clearCache() {
259: synchronized (c_caches) {
260: c_caches.clear();
261: }
262: }
263:
264: public static void clearCache(String variation) {
265: if (variation == null)
266: clearCache();
267: else if (c_caches.containsKey(variation)) {
268: synchronized (c_caches) {
269: c_caches.remove(variation);
270: }
271: }
272: }
273:
274: public static void main(String[] args) {
275: try {
276: System.out
277: .println(getClassMetaData(
278: "org.jaffa.persistence.domainobjects.CategoryOfInstrument",
279: null));
280: } catch (Exception e) {
281: e.printStackTrace();
282: }
283: }
284: }
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