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1 package org.drools.io; 2 3 /* 4 $Id: RuleSetLoader.java,v 1.4 2003/06/19 09:27:10 tdiesler Exp $ 5 6 Copyright 2002 (C) The Werken Company. All Rights Reserved. 7 8 Redistribution and use of this software and associated documentation 9 ("Software"), with or without modification, are permitted provided 10 that the following conditions are met: 11 12 1. Redistributions of source code must retain copyright 13 statements and notices. Redistributions must also contain a 14 copy of this document. 15 16 2. Redistributions in binary form must reproduce the 17 above copyright notice, this list of conditions and the 18 following disclaimer in the documentation and/or other 19 materials provided with the distribution. 20 21 3. The name "drools" must not be used to endorse or promote 22 products derived from this Software without prior written 23 permission of The Werken Company. For written permission, 24 please contact bob@werken.com. 25 26 4. Products derived from this Software may not be called "drools" 27 nor may "drools" appear in their names without prior written 28 permission of The Werken Company. "drools" is a registered 29 trademark of The Werken Company. 30 31 5. Due credit should be given to The Werken Company. 32 (http://drools.werken.com/). 33 34 THIS SOFTWARE IS PROVIDED BY THE WERKEN COMPANY AND CONTRIBUTORS 35 ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT 36 NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 37 FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 38 THE WERKEN COMPANY OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 39 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 40 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 41 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 42 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 43 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 44 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 45 OF THE POSSIBILITY OF SUCH DAMAGE. 46 47 */ 48 49 import org.drools.RuleBase; 50 import org.drools.rule.RuleSet; 51 import org.drools.tags.rule.RuleTagLibrary; 52 53 import org.apache.commons.jelly.Script; 54 import org.apache.commons.jelly.JellyContext; 55 import org.apache.commons.jelly.XMLOutput; 56 import org.apache.commons.jelly.parser.XMLParser; 57 58 import java.io.IOException; 59 import java.io.Reader; 60 import java.io.InputStream; 61 import java.io.InputStreamReader; 62 import java.net.URL; 63 import java.util.ArrayList; 64 import java.util.List; 65 import java.util.Iterator; 66 import java.util.HashMap; 67 68 /*** Loads <code>RuleSet</code> definitions from XML descriptor. 69 * 70 * @author <a href="mailto:bob@eng.werken.com">bob mcwhirter</a> 71 * 72 * @version $Id: RuleSetLoader.java,v 1.4 2003/06/19 09:27:10 tdiesler Exp $ 73 */ 74 public class RuleSetLoader 75 { 76 // ------------------------------------------------------------ 77 // Instance members 78 // ------------------------------------------------------------ 79 80 /*** Rule-sets. */ 81 private List ruleSets; 82 83 /*** 84 * Cache a list of RuleSet objects, key is the url. 85 * This is a temporary workaround for the OutOfMemoryError in OutOfMemory when a script is parsed repeatedly. 86 */ 87 private static HashMap ruleSetCache = new HashMap(); 88 89 // ------------------------------------------------------------ 90 // Constructors 91 // ------------------------------------------------------------ 92 93 /*** Construct. 94 */ 95 public RuleSetLoader() 96 { 97 // intentionally left blank 98 } 99 100 // ------------------------------------------------------------ 101 // Instance methods 102 // ------------------------------------------------------------ 103 104 /*** Add a <code>RuleSet</code> to this loader. 105 * 106 * @param ruleSet The rule-set to add. 107 */ 108 public void addRuleSet(RuleSet ruleSet) 109 { 110 this.ruleSets.add(ruleSet); 111 } 112 113 /*** Load <code>RuleSet</code> definitions from a Reader. 114 * 115 * @param reader The Reader of the rule-set definitions. 116 * 117 * @return The list of loaded rule-sets. 118 * 119 * @throws IOException If an IO errors occurs. 120 * @throws Exception If an error occurs evaluating the definition. 121 */ 122 public List load(Reader reader) throws IOException, Exception 123 { 124 125 this.ruleSets = new ArrayList(); 126 127 XMLParser parser = new XMLParser(); 128 129 JellyContext context = new JellyContext(); 130 131 context.registerTagLibrary("http://drools.org/rules", 132 new RuleTagLibrary()); 133 134 context.setVariable("org.drools.io.RuleSetLoader", 135 this); 136 137 parser.setContext(context); 138 139 Script script = parser.parse(reader); 140 141 XMLOutput output = XMLOutput.createXMLOutput(System.err, 142 false); 143 144 script.run(context, 145 output); 146 147 List answer = this.ruleSets; 148 149 this.ruleSets = null; 150 151 return answer; 152 } 153 154 /*** Load <code>RuleSet</code> definitions from a URL. 155 * 156 * @param url The URL of the rule-set definitions. 157 * 158 * @return The list of loaded rule-sets. 159 * 160 * @throws IOException If an IO errors occurs. 161 * @throws Exception If an error occurs evaluating the definition. 162 */ 163 public List load(URL url) throws IOException, Exception 164 { 165 // This is a workaround for an OutOfMemoryError in Jelly when a script is parsed repeatedly 166 // Note, the rules for a given url cannot be changed after they are chached 167 List cachedRuleSets = (List) ruleSetCache.get(url); 168 if (cachedRuleSets != null) 169 { 170 return cachedRuleSets; 171 } 172 173 InputStream urlStream = url.openStream(); 174 175 try 176 { 177 List answer = load (new InputStreamReader(urlStream)); 178 179 ruleSetCache.put(url, answer); 180 181 return answer; 182 } 183 finally 184 { 185 urlStream.close(); 186 } 187 } 188 189 /*** Load <code>RuleSet</code> deifnitions from a URL 190 * into a <code>RuleBase</code>. 191 * 192 * @param url The URL of the rule-set definitions. 193 * @param ruleBase The rule-base to populate. 194 * 195 * @throws IOException If an IO errors occurs. 196 * @throws Exception If an error occurs evaluating the definition. 197 */ 198 public void load(URL url, 199 RuleBase ruleBase) throws IOException, Exception 200 { 201 List ruleSets = load(url); 202 203 Iterator ruleSetIter = ruleSets.iterator(); 204 RuleSet eachRuleSet = null; 205 206 while (ruleSetIter.hasNext()) 207 { 208 eachRuleSet = (RuleSet) ruleSetIter.next(); 209 210 ruleBase.addRuleSet(eachRuleSet); 211 } 212 } 213 214 /*** Load <code>RuleSet</code> deifnitions from a URL. 215 * 216 * @param url The URL of the rule-set definitions. 217 * 218 * @return The list of loaded rule-sets. 219 * 220 * @throws IOException If an IO errors occurs. 221 * @throws Exception If an error occurs evaluating the definition. 222 */ 223 public List load(String url) throws IOException, Exception 224 { 225 return load(new URL(url)); 226 } 227 }

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