com.rometools.rome.io.impl.PluginManager Maven / Gradle / Ivy
/*
* Copyright 2004 Sun Microsystems, Inc.
*
* Licensed 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 com.rometools.rome.io.impl;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import com.rometools.rome.feed.impl.ConfigurableClassLoader;
import com.rometools.rome.io.DelegatingModuleGenerator;
import com.rometools.rome.io.DelegatingModuleParser;
import com.rometools.rome.io.WireFeedGenerator;
import com.rometools.rome.io.WireFeedParser;
public abstract class PluginManager {
private final String[] propertyValues;
private final List keys;
private final WireFeedParser parentParser;
private final WireFeedGenerator parentGenerator;
private Map pluginsMap;
private List pluginsList;
/**
* Creates a PluginManager
*
* @param propertyKey property key defining the plugins classes
*
*/
protected PluginManager(final String propertyKey) {
this(propertyKey, null, null);
}
protected PluginManager(final String propertyKey, final WireFeedParser parentParser, final WireFeedGenerator parentGenerator) {
this.parentParser = parentParser;
this.parentGenerator = parentGenerator;
propertyValues = PropertiesLoader.getPropertiesLoader().getTokenizedProperty(propertyKey, ", ");
loadPlugins();
pluginsMap = Collections.unmodifiableMap(pluginsMap);
pluginsList = Collections.unmodifiableList(pluginsList);
keys = Collections.unmodifiableList(new ArrayList(pluginsMap.keySet()));
}
protected abstract String getKey(T obj);
protected List getKeys() {
return keys;
}
protected List getPlugins() {
return pluginsList;
}
protected Map getPluginMap() {
return pluginsMap;
}
protected T getPlugin(final String key) {
return pluginsMap.get(key);
}
// PRIVATE - LOADER PART
private void loadPlugins() {
final List finalPluginsList = new ArrayList();
pluginsList = new ArrayList();
pluginsMap = new HashMap();
String className = null;
try {
final Class[] classes = getClasses();
for (final Class clazz : classes) {
className = clazz.getName();
final T plugin = clazz.newInstance();
if (plugin instanceof DelegatingModuleParser) {
((DelegatingModuleParser) plugin).setFeedParser(parentParser);
}
if (plugin instanceof DelegatingModuleGenerator) {
((DelegatingModuleGenerator) plugin).setFeedGenerator(parentGenerator);
}
pluginsMap.put(getKey(plugin), plugin);
// to preserve the order of definition in the rome.properties files
pluginsList.add(plugin);
}
final Collection plugins = pluginsMap.values();
for (final T plugin : plugins) {
// to remove overridden plugin impls
finalPluginsList.add(plugin);
}
final Iterator iterator = pluginsList.iterator();
while (iterator.hasNext()) {
final T plugin = iterator.next();
if (!finalPluginsList.contains(plugin)) {
iterator.remove();
}
}
} catch (final Exception ex) {
throw new RuntimeException("could not instantiate plugin " + className, ex);
} catch (final ExceptionInInitializerError er) {
throw new RuntimeException("could not instantiate plugin " + className, er);
}
}
/**
* Loads and returns the classes defined in the properties files. If the system property
* "rome.pluginmanager.useloadclass" is set to true then classLoader.loadClass will be used to
* load classes (instead of Class.forName). This is designed to improve OSGi compatibility.
* Further information can be found in https://rome.dev.java.net/issues/show_bug.cgi?id=118
*
*
* @return array containing the classes defined in the properties files.
* @throws java.lang.ClassNotFoundException thrown if one of the classes defined in the
* properties file cannot be loaded and hard failure is ON.
*
*/
@SuppressWarnings("unchecked")
private Class[] getClasses() throws ClassNotFoundException {
final ClassLoader classLoader = ConfigurableClassLoader.INSTANCE.getClassLoader();
final List> classes = new ArrayList>();
final boolean useLoadClass = Boolean.valueOf(System.getProperty("rome.pluginmanager.useloadclass", "false")).booleanValue();
for (final String propertyValue : propertyValues) {
final Class mClass;
if (useLoadClass) {
mClass = (Class) classLoader.loadClass(propertyValue);
} else {
mClass = (Class) Class.forName(propertyValue, true, classLoader);
}
classes.add(mClass);
}
final Class[] array = new Class[classes.size()];
classes.toArray(array);
return array;
}
}