org.apache.commons.digester.plugins.strategies.FinderFromResource Maven / Gradle / Ivy
/* $Id: FinderFromResource.java 729125 2008-12-23 21:21:07Z rahul $
*
* 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 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 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 {
/**
* Name of xml attribute on the plugin declaration which is used
* to configure rule-loading for that declaration.
*/
public static String DFLT_RESOURCE_ATTR = "resource";
/** See {@link #findLoader}. */
private String resourceAttr;
/** Constructor. */
public FinderFromResource() {
this(DFLT_RESOURCE_ATTR);
}
/** See {@link #findLoader}. */
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.
*/
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.
*/
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(java.io.IOException ioe) {
throw new PluginException(
"Unable to close stream for resource [" +
resourceName + "]", ioe);
}
}
}
}