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Commons Digester example source code file (FinderFromDfltClass.java)

This example Commons Digester source code file (FinderFromDfltClass.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, class, dflt_method_name, dflt_method_name, dflt_ruleclass_suffix, finderfromdfltclass, finderfromdfltclass, loaderfromclass, override, properties, rulefinder, ruleloader, string, string, util

The Commons Digester FinderFromDfltClass.java source code

/* $Id: FinderFromDfltClass.java 992106 2010-09-02 20:29:25Z 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 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.
     * <p>
     * If there is no such class, then just return null.
     * <p>
     * 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:
     * <code> public static void xxxxx(Digester d, String patternPrefix); 
     */
    @Override
    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) {
            // nope, no rule-info class in the classpath
            return null;
        }

        if (methodName == null) {
            methodName = DFLT_METHOD_NAME;
        }
        
        return new LoaderFromClass(rulesClass, methodName);
    }
}

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