org.apache.commons.digester3.plugins.strategies.FinderFromResource Maven / Gradle / Ivy
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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
*/
public class FinderFromResource
extends RuleFinder
{
/**
* 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 {@link #findLoader}. */
private final String resourceAttr;
/** Constructor. */
public FinderFromResource()
{
this( DFLT_RESOURCE_ATTR );
}
/**
* 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.
*
* @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.
*
* @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 );
}
}
}
}