package org.apache.lucene.index;
/**
* 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.io.IOException;
import org.apache.lucene.store.Directory;
/**
* Provides a {@link DirPayloadProcessor} to be used for a {@link Directory}.
* This allows using different {@link DirPayloadProcessor}s for different
* directories, for e.g. to perform different processing of payloads of
* different directories.
* <p>
* <b>NOTE:</b> to avoid processing payloads of certain directories, you can
* return <code>null</code> in {@link #getDirProcessor}.
* <p>
* <b>NOTE:</b> it is possible that the same {@link DirPayloadProcessor} will be
* requested for the same {@link Directory} concurrently. Therefore, to avoid
* concurrency issues you should return different instances for different
* threads. Usually, if your {@link DirPayloadProcessor} does not maintain state
* this is not a problem. The merge code ensures that the
* {@link DirPayloadProcessor} instance you return will be accessed by one
* thread to obtain the {@link PayloadProcessor}s for different terms.
*
* @lucene.experimental
*/
public abstract class PayloadProcessorProvider {
/**
* Returns a {@link PayloadProcessor} for a given {@link Term} which allows
* processing the payloads of different terms differently. If you intent to
* process all your payloads the same way, then you can ignore the given term.
* <p>
* <b>NOTE:</b> if you protect your {@link DirPayloadProcessor} from
* concurrency issues, then you shouldn't worry about any such issues when
* {@link PayloadProcessor}s are requested for different terms.
*/
public static abstract class DirPayloadProcessor {
/** Returns a {@link PayloadProcessor} for the given term. */
public abstract PayloadProcessor getProcessor(Term term) throws IOException;
}
/**
* Processes the given payload. One should call {@link #payloadLength()} to
* get the length of the processed payload.
*
* @lucene.experimental
*/
public static abstract class PayloadProcessor {
/** Returns the length of the payload that was returned by {@link #processPayload}. */
public abstract int payloadLength() throws IOException;
/**
* Process the incoming payload and returns the resulting byte[]. Note that
* a new array might be allocated if the given array is not big enough. The
* length of the new payload data can be obtained via
* {@link #payloadLength()}.
*/
public abstract byte[] processPayload(byte[] payload, int start, int length) throws IOException;
}
/**
* Returns a {@link DirPayloadProcessor} for the given {@link Directory},
* through which {@link PayloadProcessor}s can be obtained for each
* {@link Term}, or <code>null</code> if none should be used.
*/
public abstract DirPayloadProcessor getDirProcessor(Directory dir) throws IOException;
}