Commons Digester example source code file (FinderFromMethod.java)

This example Commons Digester source code file (FinderFromMethod.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_attr, dflt_method_attr, finderfrommethod, finderfrommethod, loaderfromclass, override, pluginexception, properties, rulefinder, ruleloader, ruleloader, string, string, util

The Commons Digester FinderFromMethod.java source code

/* $Id: FinderFromMethod.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 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 expects the caller to specify a methodname
 * as a plugin property, where the method exists on the plugin class.
 *
 * @since 1.6
 */

public class FinderFromMethod extends RuleFinder {
    /**
     * Xml attribute that needs to be present on a plugin declaration
     * in order to specify the method to load rules from.
     */
    public static String DFLT_METHOD_ATTR = "method";
    
    /** See {@link #findLoader}. */
    private String methodAttr;
    
    /** Constructor. */
    public FinderFromMethod() {
        this(DFLT_METHOD_ATTR);
    }

    /** See {@link #findLoader}. */
    public FinderFromMethod(String methodAttr) { 
        this.methodAttr = methodAttr;
    }
    
    /**
     * If there exists a property with the name matching constructor param
     * methodAttr, then locate the appropriate Method on the plugin class 
     * and return an object encapsulating that info.
     * <p>
     * If there is no matching property provided, 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 {

        String methodName = p.getProperty(methodAttr);
        if (methodName == null) {
            // nope, user hasn't requested dynamic rules to be loaded
            // from a specific class.
            return null;
        }
        
        return new LoaderFromClass(pluginClass, methodName);
    }
}