org.apache.lucene.analysis.util.AnalysisSPILoader Maven / Gradle / Ivy
package org.apache.lucene.analysis.util;
/*
* 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.util.Arrays;
import java.util.Collections;
import java.util.Locale;
import java.util.Map;
import java.util.LinkedHashMap;
import java.util.Set;
import java.util.ServiceConfigurationError;
import org.apache.lucene.util.SPIClassIterator;
/**
* Helper class for loading named SPIs from classpath (e.g. Tokenizers, TokenStreams).
* @lucene.internal
*/
final class AnalysisSPILoader {
private volatile Map> services = Collections.emptyMap();
private final Class clazz;
private final String[] suffixes;
public AnalysisSPILoader(Class clazz) {
this(clazz, new String[] { clazz.getSimpleName() });
}
public AnalysisSPILoader(Class clazz, ClassLoader loader) {
this(clazz, new String[] { clazz.getSimpleName() }, loader);
}
public AnalysisSPILoader(Class clazz, String[] suffixes) {
this(clazz, suffixes, Thread.currentThread().getContextClassLoader());
}
public AnalysisSPILoader(Class clazz, String[] suffixes, ClassLoader classloader) {
this.clazz = clazz;
this.suffixes = suffixes;
// if clazz' classloader is not a parent of the given one, we scan clazz's classloader, too:
final ClassLoader clazzClassloader = clazz.getClassLoader();
if (clazzClassloader != null && !SPIClassIterator.isParentClassLoader(clazzClassloader, classloader)) {
reload(clazzClassloader);
}
reload(classloader);
}
/**
* Reloads the internal SPI list from the given {@link ClassLoader}.
* Changes to the service list are visible after the method ends, all
* iterators (e.g., from {@link #availableServices()},...) stay consistent.
*
* NOTE: Only new service providers are added, existing ones are
* never removed or replaced.
*
*
This method is expensive and should only be called for discovery
* of new service providers on the given classpath/classloader!
*/
public synchronized void reload(ClassLoader classloader) {
final LinkedHashMap> services =
new LinkedHashMap<>(this.services);
final SPIClassIterator loader = SPIClassIterator.get(clazz, classloader);
while (loader.hasNext()) {
final Class service = loader.next();
final String clazzName = service.getSimpleName();
String name = null;
for (String suffix : suffixes) {
if (clazzName.endsWith(suffix)) {
name = clazzName.substring(0, clazzName.length() - suffix.length()).toLowerCase(Locale.ROOT);
break;
}
}
if (name == null) {
throw new ServiceConfigurationError("The class name " + service.getName() +
" has wrong suffix, allowed are: " + Arrays.toString(suffixes));
}
// only add the first one for each name, later services will be ignored
// this allows to place services before others in classpath to make
// them used instead of others
//
// TODO: Should we disallow duplicate names here?
// Allowing it may get confusing on collisions, as different packages
// could contain same factory class, which is a naming bug!
// When changing this be careful to allow reload()!
if (!services.containsKey(name)) {
services.put(name, service);
}
}
this.services = Collections.unmodifiableMap(services);
}
public S newInstance(String name, Map args) {
final Class service = lookupClass(name);
try {
return service.getConstructor(Map.class).newInstance(args);
} catch (Exception e) {
throw new IllegalArgumentException("SPI class of type "+clazz.getName()+" with name '"+name+"' cannot be instantiated. " +
"This is likely due to a misconfiguration of the java class '" + service.getName() + "': ", e);
}
}
public Class lookupClass(String name) {
final Class service = services.get(name.toLowerCase(Locale.ROOT));
if (service != null) {
return service;
} else {
throw new IllegalArgumentException("A SPI class of type "+clazz.getName()+" with name '"+name+"' does not exist. "+
"You need to add the corresponding JAR file supporting this SPI to your classpath. "+
"The current classpath supports the following names: "+availableServices());
}
}
public Set availableServices() {
return services.keySet();
}
}