org.apache.commons.digester.plugins.strategies.FinderFromDfltClass Maven / Gradle / Ivy
/* $Id: FinderFromDfltClass.java 729125 2008-12-23 21:21:07Z rahul $
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.digester.plugins.strategies;
import java.util.Properties;
import org.apache.commons.digester.Digester;
import org.apache.commons.digester.plugins.RuleFinder;
import org.apache.commons.digester.plugins.RuleLoader;
import org.apache.commons.digester.plugins.PluginException;
/**
* A rule-finding algorithm which looks for a method with a specific name
* on a class whose name is derived from the plugin class name.
*
* @since 1.6
*/
public class FinderFromDfltClass extends RuleFinder {
public static String DFLT_RULECLASS_SUFFIX = "RuleInfo";
public static String DFLT_METHOD_NAME = "addRules";
private String rulesClassSuffix;
private String methodName;
/** See {@link #findLoader}. */
public FinderFromDfltClass() {
this(DFLT_RULECLASS_SUFFIX, DFLT_METHOD_NAME);
}
/**
* Create a rule-finder which invokes a method on a class whenever
* dynamic rules for a plugin need to be loaded. See the findRules
* method for more info.
*
* @param rulesClassSuffix must be non-null.
* @param methodName may be null.
*/
public FinderFromDfltClass(String rulesClassSuffix, String methodName) {
this.rulesClassSuffix = rulesClassSuffix;
this.methodName = methodName;
}
/**
* If there exists a class whose name is the plugin class name + the
* suffix specified to the constructor, then load that class, locate
* the appropriate rules-adding method on that class, and return an
* object encapsulating that info.
*
* If there is no such class, then just return null.
*
* The returned object (when non-null) will invoke the target method
* on the selected class whenever its addRules method is invoked. The
* target method is expected to have the following prototype:
* public static void xxxxx(Digester d, String patternPrefix);
*/
public RuleLoader findLoader(Digester digester, Class pluginClass, Properties p)
throws PluginException {
String rulesClassName = pluginClass.getName() + rulesClassSuffix;
Class rulesClass = null;
try {
rulesClass = digester.getClassLoader().loadClass(rulesClassName);
} catch(ClassNotFoundException cnfe) {
// ok, ignore
}
if (rulesClass == null) {
// nope, no rule-info class in the classpath
return null;
}
if (methodName == null) {
methodName = DFLT_METHOD_NAME;
}
return new LoaderFromClass(rulesClass, methodName);
}
}