package org.apache.commons.digester3.plugins.strategies;

/*
 * 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.
 */

import java.util.Properties;

import org.apache.commons.digester3.Digester;
import org.apache.commons.digester3.plugins.PluginException;
import org.apache.commons.digester3.plugins.RuleFinder;
import org.apache.commons.digester3.plugins.RuleLoader;

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/**
 * 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
{

    
Default XML attribute that needs to be present on a plugin declaration in order to specify the method
to load rules from.
/**
     * Default XML attribute that needs to be present on a plugin declaration in order to specify the method
     * to load rules from.
     */
    private static final String DFLT_METHOD_ATTR = "method";

    
See findLoader. /** See {@link #findLoader}. */
    private final String methodAttr;

    
Constructor. /** Constructor. */
    public FinderFromMethod()
    {
        this( DFLT_METHOD_ATTR );
    }

    
See findLoader. 
Params:
methodAttr – The XML attribute that needs to be present on a plugin declaration in order to specify the
       method to load rules from./**
     * See {@link #findLoader}.
     *
     * @param methodAttr The XML attribute that needs to be present on a plugin declaration in order to specify the
     *        method to load rules from.
     */
    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.

If there is no matching property provided, then just return null.

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:
 public static void xxxxx(Digester d, String patternPrefix); 
Params:
d – The digester instance where locating plugin classes
pluginClass – The plugin Java class
p – The properties object that holds any xml attributes the user may have specified on the plugin
         declaration in order to indicate how to locate the plugin rules.
Throws:
PluginException – if the algorithm finds a source of rules, but there is something invalid
        about that source.
Returns:
a source of digester rules for the specified plugin class./**
     * 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); </code>
     *
     * @param d The digester instance where locating plugin classes
     * @param pluginClass The plugin Java class
     * @param p The properties object that holds any xml attributes the user may have specified on the plugin
     *          declaration in order to indicate how to locate the plugin rules.
     * @return a source of digester rules for the specified plugin class.
     * @throws PluginException if the algorithm finds a source of rules, but there is something invalid
     *         about that source.
     */
    @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 );
    }

}