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/*
* Copyright 2013 Decebal Suiu
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this work except in compliance with
* the License. You may obtain a copy of the License in the LICENSE file, or 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 ro.fortsoft.pf4j;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.util.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The default implementation for ExtensionFinder.
* All extensions declared in a plugin are indexed in a file "META-INF/extensions.idx".
* This class lookup extensions in all extensions index files "META-INF/extensions.idx".
*
* @author Decebal Suiu
*/
public class DefaultExtensionFinder implements ExtensionFinder, PluginStateListener {
private static final Logger log = LoggerFactory.getLogger(DefaultExtensionFinder.class);
private PluginManager pluginManager;
private ExtensionFactory extensionFactory;
private volatile Map<String, Set<String>> entries; // cache by pluginId
public DefaultExtensionFinder(PluginManager pluginManager) {
this.pluginManager = pluginManager;
this.extensionFactory = createExtensionFactory();
}
@Override
public <T> List<ExtensionWrapper<T>> find(Class<T> type) {
log.debug("Checking extension point '{}'", type.getName());
if (!isExtensionPoint(type)) {
log.warn("'{}' is not an extension point", type.getName());
return Collections.emptyList(); // or return null ?!
}
log.debug("Finding extensions for extension point '{}'", type.getName());
readIndexFiles();
List<ExtensionWrapper<T>> result = new ArrayList<ExtensionWrapper<T>>();
for (Map.Entry<String, Set<String>> entry : entries.entrySet()) {
String pluginId = entry.getKey();
PluginWrapper pluginWrapper = pluginManager.getPlugin(pluginId);
if (PluginState.STARTED != pluginWrapper.getPluginState()) {
continue;
}
Set<String> extensionClassNames = entry.getValue();
for (String className : extensionClassNames) {
try {
Class<?> extensionType = pluginManager.getPluginClassLoader(pluginId).loadClass(className);
log.debug("Checking extension type '{}'", extensionType.getName());
if (type.isAssignableFrom(extensionType)) {
Object instance = extensionFactory.create(extensionType);
if (instance != null) {
Extension extension = extensionType.getAnnotation(Extension.class);
log.debug("Added extension '{}' with ordinal {}", extensionType.getName(), extension.ordinal());
result.add(new ExtensionWrapper<T>(type.cast(instance), extension.ordinal()));
}
} else {
log.warn("'{}' is not an extension for extension point '{}'", extensionType.getName(), type.getName());
}
} catch (ClassNotFoundException e) {
log.error(e.getMessage(), e);
}
}
}
if (entries.isEmpty()) {
log.debug("No extensions found for extension point '{}'", type.getName());
} else {
log.debug("Found {} extensions for extension point '{}'", entries.size(), type.getName());
}
// sort by "ordinal" property
Collections.sort(result);
return result;
}
@Override
public Set<String> findClassNames(String pluginId) {
readIndexFiles();
return entries.get(pluginId);
}
@Override
public void pluginStateChanged(PluginStateEvent event) {
// TODO optimize (do only for some transitions)
// clear cache
entries = null;
}
/**
* Add the possibility to override the ExtensionFactory.
* The default implementation uses Class.newInstance() method.
*/
protected ExtensionFactory createExtensionFactory() {
return new ExtensionFactory() {
@Override
public Object create(Class<?> extensionType) {
log.debug("Create instance for extension '{}'", extensionType.getName());
try {
return extensionType.newInstance();
} catch (InstantiationException e) {
log.error(e.getMessage(), e);
} catch (IllegalAccessException e) {
log.error(e.getMessage(), e);
}
return null;
}
};
}
private Map<String, Set<String>> readIndexFiles() {
// checking cache
if (entries != null) {
return entries;
}
entries = new HashMap<String, Set<String>>();
List<PluginWrapper> plugins = pluginManager.getPlugins();
for (PluginWrapper plugin : plugins) {
String pluginId = plugin.getDescriptor().getPluginId();
log.debug("Reading extensions index file for plugin '{}'", pluginId);
Set<String> entriesPerPlugin = new HashSet<String>();
try {
URL url = plugin.getPluginClassLoader().getResource(ExtensionsIndexer.EXTENSIONS_RESOURCE);
log.debug("Read '{}'", url.getFile());
Reader reader = new InputStreamReader(url.openStream(), "UTF-8");
ExtensionsIndexer.readIndex(reader, entriesPerPlugin);
if (entriesPerPlugin.isEmpty()) {
log.debug("No extensions found");
} else {
log.debug("Found possible {} extensions:", entriesPerPlugin.size());
for (String entry : entriesPerPlugin) {
log.debug(" " + entry);
}
}
entries.put(pluginId, entriesPerPlugin);
} catch (IOException e) {
log.error(e.getMessage(), e);
}
}
return entries;
}
private boolean isExtensionPoint(Class<?> type) {
return ExtensionPoint.class.isAssignableFrom(type);
}
/**
* Creates an extension instance.
*/
public static interface ExtensionFactory {
public Object create(Class<?> extensionType);
}
}
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