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.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
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 user to specify an absolute or relative path in the plugin declaration.

The file is expected to contain Digester rules in xmlrules format.
Since:
1.6/**
 * 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
{

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

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

    
See findLoader. /** See {@link #findLoader}. */
    public FinderFromFile()
    {
        this( DFLT_FILENAME_ATTR );
    }

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

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

The returned object (when non-null) will add the selected rules to the digester whenever its addRules method is
invoked.
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 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.
     *
     * @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 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 ( IOException ioe )
            {
                throw new PluginException( "Unable to close stream for file [" + rulesFileName + "]", ioe );
            }
        }
    }

}