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Commons Digester example source code file (FinderFromFile.java)

This example Commons Digester source code file (FinderFromFile.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

dflt_filename_attr, finderfromfile, finderfromfile, inputstream, io, loaderfromstream, override, pluginexception, pluginexception, properties, ruleloader, string, string, unable, unable, util

The Commons Digester FinderFromFile.java source code

/* $Id: FinderFromFile.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.io.InputStream;
import java.io.FileInputStream;
import java.io.IOException;

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 user to specify an absolute
 * or relative path in the plugin declaration.
 * <p>
 * The file is expected to contain Digester rules in xmlrules format.
 *
 * @since 1.6
 */

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

    /** See {@link #findLoader}. */
    public FinderFromFile(String filenameAttr) { 
        this.filenameAttr = filenameAttr;
    }
    
    /**
     * If there exists a property with the name 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 matching property provided, 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 rulesFileName = p.getProperty(filenameAttr);
        if (rulesFileName == null) {
            // nope, user hasn't requested dynamic rules to be loaded
            // from a specific file.
            return null;
        }
        
        InputStream is = null;
        try {
            is = new FileInputStream(rulesFileName);
        } catch(IOException ioe) {
            throw new PluginException(
                "Unable to process file [" + rulesFileName + "]", ioe);
        }
        
        try {
            RuleLoader loader = new LoaderFromStream(is);
            return loader;
        } catch(Exception e) {
            throw new PluginException(
                "Unable to load xmlrules from file [" + 
                rulesFileName + "]", e);
        } finally {
            try {
                is.close();
            } catch(java.io.IOException ioe) {
                throw new PluginException(
                    "Unable to close stream for file [" + 
                    rulesFileName + "]", ioe);
            }
        }
    }
}

Other Commons Digester examples (source code examples)

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