| /* |
| * 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. |
| */ |
| package org.apache.lucene.index; |
| |
| |
| import java.io.IOException; |
| import java.util.List; |
| |
| /** |
| * A FilterDirectoryReader wraps another DirectoryReader, allowing implementations |
| * to transform or extend it. |
| * |
| * Subclasses should implement doWrapDirectoryReader to return an instance of the |
| * subclass. |
| * |
| * If the subclass wants to wrap the DirectoryReader's subreaders, it should also |
| * implement a SubReaderWrapper subclass, and pass an instance to its super |
| * constructor. |
| */ |
| public abstract class FilterDirectoryReader extends DirectoryReader { |
| |
| /** Get the wrapped instance by <code>reader</code> as long as this reader is |
| * an instance of {@link FilterDirectoryReader}. */ |
| public static DirectoryReader unwrap(DirectoryReader reader) { |
| while (reader instanceof FilterDirectoryReader) { |
| reader = ((FilterDirectoryReader) reader).getDelegate(); |
| } |
| return reader; |
| } |
| |
| /** |
| * Factory class passed to FilterDirectoryReader constructor that allows |
| * subclasses to wrap the filtered DirectoryReader's subreaders. You |
| * can use this to, e.g., wrap the subreaders with specialised |
| * FilterLeafReader implementations. |
| */ |
| public static abstract class SubReaderWrapper { |
| |
| /** |
| * Wraps a list of LeafReaders |
| * @return an array of wrapped LeafReaders. The returned array might contain less elements compared to the given |
| * reader list if an entire reader is filtered out. |
| */ |
| protected LeafReader[] wrap(List<? extends LeafReader> readers) { |
| LeafReader[] wrapped = new LeafReader[readers.size()]; |
| int i = 0; |
| for (LeafReader reader : readers) { |
| LeafReader wrap = wrap(reader); |
| assert wrap != null; |
| wrapped[i++] = wrap; |
| } |
| return wrapped; |
| } |
| |
| /** Constructor */ |
| public SubReaderWrapper() {} |
| |
| /** |
| * Wrap one of the parent DirectoryReader's subreaders |
| * @param reader the subreader to wrap |
| * @return a wrapped/filtered LeafReader |
| */ |
| public abstract LeafReader wrap(LeafReader reader); |
| |
| } |
| |
| /** The filtered DirectoryReader */ |
| protected final DirectoryReader in; |
| |
| /** |
| * Create a new FilterDirectoryReader that filters a passed in DirectoryReader, |
| * using the supplied SubReaderWrapper to wrap its subreader. |
| * @param in the DirectoryReader to filter |
| * @param wrapper the SubReaderWrapper to use to wrap subreaders |
| */ |
| public FilterDirectoryReader(DirectoryReader in, SubReaderWrapper wrapper) throws IOException { |
| super(in.directory(), wrapper.wrap(in.getSequentialSubReaders()), null); |
| this.in = in; |
| } |
| |
| /** |
| * Called by the doOpenIfChanged() methods to return a new wrapped DirectoryReader. |
| * |
| * Implementations should just return an instantiation of themselves, wrapping the |
| * passed in DirectoryReader. |
| * |
| * @param in the DirectoryReader to wrap |
| * @return the wrapped DirectoryReader |
| */ |
| protected abstract DirectoryReader doWrapDirectoryReader(DirectoryReader in) throws IOException; |
| |
| private final DirectoryReader wrapDirectoryReader(DirectoryReader in) throws IOException { |
| return in == null ? null : doWrapDirectoryReader(in); |
| } |
| |
| @Override |
| protected final DirectoryReader doOpenIfChanged() throws IOException { |
| return wrapDirectoryReader(in.doOpenIfChanged()); |
| } |
| |
| @Override |
| protected final DirectoryReader doOpenIfChanged(IndexCommit commit) throws IOException { |
| return wrapDirectoryReader(in.doOpenIfChanged(commit)); |
| } |
| |
| @Override |
| protected final DirectoryReader doOpenIfChanged(IndexWriter writer, boolean applyAllDeletes) throws IOException { |
| return wrapDirectoryReader(in.doOpenIfChanged(writer, applyAllDeletes)); |
| } |
| |
| @Override |
| public long getVersion() { |
| return in.getVersion(); |
| } |
| |
| @Override |
| public boolean isCurrent() throws IOException { |
| return in.isCurrent(); |
| } |
| |
| @Override |
| public IndexCommit getIndexCommit() throws IOException { |
| return in.getIndexCommit(); |
| } |
| |
| @Override |
| protected void doClose() throws IOException { |
| in.close(); |
| } |
| |
| /** Returns the wrapped {@link DirectoryReader}. */ |
| public DirectoryReader getDelegate() { |
| return in; |
| } |
| } |