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.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 a resource name (ie a file in the classpath). The file is
expected to contain Digester rules in xmlrules format.
Since:
1.6/**
 * A rule-finding algorithm which expects the user to specify a resource name (ie a file in the classpath). The file is
 * expected to contain Digester rules in xmlrules format.
 * 
 * @since 1.6
 */
public class FinderFromResource
    extends RuleFinder
{

    
Default name of xml attribute on the plugin declaration which is used to configure rule-loading
for that declaration.
/**
     * Default name of xml attribute on the plugin declaration which is used to configure rule-loading
     * for that declaration.
     */
    private static final String DFLT_RESOURCE_ATTR = "resource";

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

    
Constructor. /** Constructor. */
    public FinderFromResource()
    {
        this( DFLT_RESOURCE_ATTR );
    }

    
See findLoader. 
Params:
resourceAttr – Name of xml attribute on the plugin declaration which is used to configure rule-loading
       for that declaration/**
     * See {@link #findLoader}.
     *
     * @param resourceAttr Name of xml attribute on the plugin declaration which is used to configure rule-loading
     *        for that declaration
     */
    public FinderFromResource( String resourceAttr )
    {
        this.resourceAttr = resourceAttr;
    }

    
If there exists a property with the name matching constructor param resourceAttr, 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 matching constructor param resourceAttr, 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 resourceName = p.getProperty( resourceAttr );
        if ( resourceName == null )
        {
            // nope, user hasn't requested dynamic rules to be loaded
            // from a specific file.
            return null;
        }

        InputStream is = pluginClass.getClassLoader().getResourceAsStream( resourceName );

        if ( is == null )
        {
            throw new PluginException( "Resource " + resourceName + " not found." );
        }

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

    
Open the specified resource file (ie a file in the classpath, including being within a jar in the classpath), run
it through the xmlrules module and return an object encapsulating those rules.
Params:
d – is the digester into which rules will eventually be loaded.
pluginClass – is the class whose xml params the rules are parsing.
is – is where the xmlrules will be read from, and must be non-null.
resourceName – is a string describing the source of the xmlrules, for use in generating error messages.
Throws:
PluginException – if any error occurs
Returns:
a source of digester rules for the specified plugin class./**
     * Open the specified resource file (ie a file in the classpath, including being within a jar in the classpath), run
     * it through the xmlrules module and return an object encapsulating those rules.
     * 
     * @param d is the digester into which rules will eventually be loaded.
     * @param pluginClass is the class whose xml params the rules are parsing.
     * @param is is where the xmlrules will be read from, and must be non-null.
     * @param resourceName is a string describing the source of the xmlrules, for use in generating error messages.
     * @return a source of digester rules for the specified plugin class.
     * @throws PluginException if any error occurs
     */
    public static RuleLoader loadRules( Digester d, Class<?> pluginClass, InputStream is, String resourceName )
        throws PluginException
    {
        try
        {
            RuleLoader loader = new LoaderFromStream( is );
            return loader;
        }
        catch ( Exception e )
        {
            throw new PluginException( "Unable to load xmlrules from resource [" + resourceName + "]", e );
        }
        finally
        {
            try
            {
                is.close();
            }
            catch ( IOException ioe )
            {
                throw new PluginException( "Unable to close stream for resource [" + resourceName + "]", ioe );
            }
        }
    }

}