Commons Digester example source code file (FinderFromDfltMethod.java)

This example Commons Digester source code file (FinderFromDfltMethod.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

class, dflt_method_name, finderfromdfltmethod, finderfromdfltmethod, loaderfromclass, loaderfromclass, method, override, properties, reflection, rulefinder, ruleloader, ruleloader, string, string, util

The Commons Digester FinderFromDfltMethod.java source code

/* $Id: FinderFromDfltMethod.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * 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 java.lang.reflect.Method;

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 the plugin class.
 *
 * @since 1.6
 */

public class FinderFromDfltMethod extends RuleFinder {
    public static String DFLT_METHOD_NAME = "addRules";

    private String methodName;
    
    /** See {@link #findLoader}. */
    public FinderFromDfltMethod() { 
        this(DFLT_METHOD_NAME);
    }

    /**
     * Create a rule-finder which invokes a specific method on the plugin
     * class whenever dynamic rules for a plugin need to be loaded. See the 
     * findRules method for more info.
     *
     * @param methodName must be non-null.
     */
    public FinderFromDfltMethod(String methodName) { 
        this.methodName = methodName;
    }
    
    /**
     * If there exists on the plugin class a method with name matching the 
     * constructor's methodName value then locate the appropriate Method on 
     * the plugin class and return an object encapsulating that info.
     * <p>
     * If there is no matching method then just return null.
     * <p>
     * The returned object (when non-null) will invoke the target method
     * on the plugin class whenever its addRules method is invoked. The
     * target method is expected to have the following prototype:
     * <code> public static void xxxxx(Digester d, String patternPrefix); 
     */
    @Override
    public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
                        throws PluginException {

        Method rulesMethod = LoaderFromClass.locateMethod(pluginClass, methodName);
        if (rulesMethod == null) {
            return null;
        }
        
        return new LoaderFromClass(pluginClass, rulesMethod);
    }
}