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Commons Digester example source code file (FinderFromDfltResource.java)

This example Commons Digester source code file (FinderFromDfltResource.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_resource_suffix, dflt_resource_suffix, finderfromdfltresource, finderfromdfltresource, inputstream, io, override, pluginexception, properties, rulefinder, ruleloader, ruleloader, string, string, util

The Commons Digester FinderFromDfltResource.java source code

/* $Id: FinderFromDfltResource.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.io.InputStream;
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 resource file in the classpath
 * whose name is derived from the plugin class name plus a specified suffix.
 * <p>
 * If the resource-file is found, then it is expected to define a set of
 * Digester rules in xmlrules format.
 *
 * @since 1.6
 */

public class FinderFromDfltResource extends RuleFinder {
    public static String DFLT_RESOURCE_SUFFIX = "RuleInfo.xml";

    private String resourceSuffix;
    
    /** See {@link #findLoader}. */
    public FinderFromDfltResource() { 
        this(DFLT_RESOURCE_SUFFIX);
    }

    /**
     * Create a rule-finder which can load an xmlrules file, cache
     * the rules away, and later add them as a plugin's custom rules
     * when that plugin is referenced.
     *
     * @param resourceSuffix must be non-null.
     */
    public FinderFromDfltResource(String resourceSuffix) { 
        this.resourceSuffix = resourceSuffix;
    }
    
    /**
     * If there exists a resource file whose name is equal to the plugin
     * class name + the suffix specified in the constructor, then
     * load that file, run it through the xmlrules module and return an object 
     * encapsulating those rules.
     * <p>
     * If there is no such resource file, then just return null.
     * <p>
     * The returned object (when non-null) will add the selected rules to
     * the digester whenever its addRules method is invoked.
     */
    @Override
    public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
                        throws PluginException {

        String resourceName = 
            pluginClass.getName().replace('.', '/') 
                    + resourceSuffix;
            
        InputStream is = 
            pluginClass.getClassLoader().getResourceAsStream(
                resourceName);

        if (is == null) {
            // ok, no such resource
            return null;
        }

        return FinderFromResource.loadRules(d, pluginClass, is, resourceName);
    }
}

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