    001    /* $Id: FinderFromDfltMethod.java 729125 2008-12-23 21:21:07Z rahul $
    002     *
    003     * Licensed to the Apache Software Foundation (ASF) under one or more
    004     * contributor license agreements.  See the NOTICE file distributed with
    005     * this work for additional information regarding copyright ownership.
    006     * The ASF licenses this file to You under the Apache License, Version 2.0
    007     * (the "License"); you may not use this file except in compliance with
    008     * the License.  You may obtain a copy of the License at
    009     *
    010     *      http://www.apache.org/licenses/LICENSE-2.0
    011     *
    012     * Unless required by applicable law or agreed to in writing, software
    013     * distributed under the License is distributed on an "AS IS" BASIS,
    014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    015     * See the License for the specific language governing permissions and
    016     * limitations under the License.
    017     */
    018
    019    package org.apache.commons.digester.plugins.strategies;
    020
    021    import java.util.Properties;
    022    import java.lang.reflect.Method;
    023
    024    import org.apache.commons.digester.Digester;
    025    import org.apache.commons.digester.plugins.RuleFinder;
    026    import org.apache.commons.digester.plugins.RuleLoader;
    027    import org.apache.commons.digester.plugins.PluginException;
    028
    029    /**
    030     * A rule-finding algorithm which looks for a method with a specific name
    031     * on the plugin class.
    032     *
    033     * @since 1.6
    034     */
    035
    036    public class FinderFromDfltMethod extends RuleFinder {
    037        public static String DFLT_METHOD_NAME = "addRules";
    038
    039        private String methodName;
    040
    041        /** See {@link #findLoader}. */
    042        public FinderFromDfltMethod() {
    043            this(DFLT_METHOD_NAME);
    044        }
    045
    046        /**
    047         * Create a rule-finder which invokes a specific method on the plugin
    048         * class whenever dynamic rules for a plugin need to be loaded. See the
    049         * findRules method for more info.
    050         *
    051         * @param methodName must be non-null.
    052         */
    053        public FinderFromDfltMethod(String methodName) {
    054            this.methodName = methodName;
    055        }
    056
    057        /**
    058         * If there exists on the plugin class a method with name matching the
    059         * constructor's methodName value then locate the appropriate Method on
    060         * the plugin class and return an object encapsulating that info.
    061         * <p>
    062         * If there is no matching method then just return null.
    063         * <p>
    064         * The returned object (when non-null) will invoke the target method
    065         * on the plugin class whenever its addRules method is invoked. The
    066         * target method is expected to have the following prototype:
    067         * <code> public static void xxxxx(Digester d, String patternPrefix); </code>
    068         */
    069        public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
    070                            throws PluginException {
    071
    072            Method rulesMethod = LoaderFromClass.locateMethod(pluginClass, methodName);
    073            if (rulesMethod == null) {
    074                return null;
    075            }
    076
    077            return new LoaderFromClass(pluginClass, rulesMethod);
    078        }
    079    }
    080