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/*
* COPIED FROM APACHE LUCENE 4.7.2
*
* Git URL: [email protected]:apache/lucene.git, tag: releases/lucene-solr/4.7.2, path: lucene/core/src/java
*
* (see https://issues.apache.org/jira/browse/OAK-10786 for details)
*/
package org.apache.lucene.codecs;
/*
* 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.Set;
import java.util.ServiceLoader; // javadocs
import org.apache.lucene.index.IndexWriterConfig; // javadocs
import org.apache.lucene.util.NamedSPILoader;
/**
* Encodes/decodes an inverted index segment.
*
* Note, when extending this class, the name ({@link #getName}) is
* written into the index. In order for the segment to be read, the
* name must resolve to your implementation via {@link #forName(String)}.
* This method uses Java's
* {@link ServiceLoader Service Provider Interface} (SPI) to resolve codec names.
*
* If you implement your own codec, make sure that it has a no-arg constructor
* so SPI can load it.
* @see ServiceLoader
*/
public abstract class Codec implements NamedSPILoader.NamedSPI {
private static final NamedSPILoader loader =
new NamedSPILoader(Codec.class);
private final String name;
/**
* Creates a new codec.
*
* The provided name will be written into the index segment: in order to
* for the segment to be read this class should be registered with Java's
* SPI mechanism (registered in META-INF/ of your jar file, etc).
* @param name must be all ascii alphanumeric, and less than 128 characters in length.
*/
protected Codec(String name) {
NamedSPILoader.checkServiceName(name);
this.name = name;
}
/** Returns this codec's name */
@Override
public final String getName() {
return name;
}
/** Encodes/decodes postings */
public abstract PostingsFormat postingsFormat();
/** Encodes/decodes docvalues */
public abstract DocValuesFormat docValuesFormat();
/** Encodes/decodes stored fields */
public abstract StoredFieldsFormat storedFieldsFormat();
/** Encodes/decodes term vectors */
public abstract TermVectorsFormat termVectorsFormat();
/** Encodes/decodes field infos file */
public abstract FieldInfosFormat fieldInfosFormat();
/** Encodes/decodes segment info file */
public abstract SegmentInfoFormat segmentInfoFormat();
/** Encodes/decodes document normalization values */
public abstract NormsFormat normsFormat();
/** Encodes/decodes live docs */
public abstract LiveDocsFormat liveDocsFormat();
/** looks up a codec by name */
public static Codec forName(String name) {
if (loader == null) {
throw new IllegalStateException("You called Codec.forName() before all Codecs could be initialized. "+
"This likely happens if you call it from a Codec's ctor.");
}
return loader.lookup(name);
}
/** returns a list of all available codec names */
public static Set availableCodecs() {
if (loader == null) {
throw new IllegalStateException("You called Codec.availableCodecs() before all Codecs could be initialized. "+
"This likely happens if you call it from a Codec's ctor.");
}
return loader.availableServices();
}
/**
* Reloads the codec list from the given {@link ClassLoader}.
* Changes to the codecs are visible after the method ends, all
* iterators ({@link #availableCodecs()},...) stay consistent.
*
* NOTE: Only new codecs are added, existing ones are
* never removed or replaced.
*
*
This method is expensive and should only be called for discovery
* of new codecs on the given classpath/classloader!
*/
public static void reloadCodecs(ClassLoader classloader) {
loader.reload(classloader);
}
private static Codec defaultCodec = Codec.forName("Lucene46");
/** expert: returns the default codec used for newly created
* {@link IndexWriterConfig}s.
*/
// TODO: should we use this, or maybe a system property is better?
public static Codec getDefault() {
return defaultCodec;
}
/** expert: sets the default codec used for newly created
* {@link IndexWriterConfig}s.
*/
public static void setDefault(Codec codec) {
defaultCodec = codec;
}
/**
* returns the codec's name. Subclasses can override to provide
* more detail (such as parameters).
*/
@Override
public String toString() {
return name;
}
}