001: /**
002: * MultiFilter.java
003: *
004: * Copyright (c) 2000 Douglass R. Cutting.
005: *
006: * This program is free software; you can redistribute it and/or modify
007: * it under the terms of the GNU General Public License as published by
008: * the Free Software Foundation; either version 2 of the License, or
009: * (at your option) any later version.
010: *
011: * This program is distributed in the hope that it will be useful,
012: * but WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
014: * GNU General Public License for more details.
015: *
016: * You should have received a copy of the GNU General Public License
017: * along with this program; if not, write to the Free Software
018: * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
019: */package dlog4j.search;
020:
021: import java.io.IOException;
022: import java.util.ArrayList;
023: import java.util.BitSet;
024: import java.util.List;
025:
026: import org.apache.lucene.index.IndexReader;
027: import org.apache.lucene.search.Filter;
028:
029: /**
030: * A Filter that logically combines multiple other Filters. An arbitrary
031: * number of Filter objects can be added to each MultiFilter. When a Query is
032: * executed with a MultiFilter, each Document in the HitList must pass every
033: * Filter in the MultiFilter filter list.<p>
034: *
035: * For example, consider a MultiFilter that is created with a FilterX filter
036: * and FilterY filter. When a search is executed with the MultiFilter, in order
037: * for Document A to appear in the results, it must pass both the FilterX
038: * <b>and</b> FilterY filters.<p>
039: *
040: * If no Filter objects are added to a MultiFilter before it is used in a
041: * search, this will have the affect of filtering out all search results.
042: *
043: * @author Matt Tucker (matt@coolservlets.com)
044: */
045: public class MultiFilter extends org.apache.lucene.search.Filter {
046:
047: /**
048: * An ArrayList to store the filters that are part of this MultiFilter. We
049: * use an ArrayList instead of a Vector for increased performance. If you
050: * require JDK1.1 support, change to a Vector.
051: */
052: private List filterList;
053:
054: /**
055: * Creates a new MultiFilter.
056: */
057: public MultiFilter() {
058: filterList = new ArrayList();
059: }
060:
061: /**
062: * Creates a new MultiFilter with the specified initial capacity. Providing
063: * an initial capacity equal to the size of the eventual MultiFilter size
064: * provides a slight performance advantage over letting the MultiFilter
065: * grow automatically.
066: *
067: * @param initialCapacity an initial capacity size for the MultiFilter.
068: */
069: public MultiFilter(int initialCapacity) {
070: filterList = new ArrayList(initialCapacity);
071: }
072:
073: /**
074: * Adds a filter to the MuliFilter filter list.
075: *
076: * @param filter a Filter to add to the MultiFilter filter list.
077: */
078: public void add(Filter filter) {
079: filterList.add(filter);
080: }
081:
082: public BitSet bits(IndexReader reader) throws IOException {
083: //Iterate through list of filters and apply the boolean AND operation
084: //on each bitSet. The AND operator has the affect that only documents
085: //that are allowed by every single filter in the filter list will be
086: //allowed by this MultiFilter.
087: int filterListSize = filterList.size();
088: if (filterListSize > 0) {
089: BitSet bits = ((Filter) filterList.get(0)).bits(reader);
090: for (int i = 1; i < filterListSize; i++) {
091: bits.and(((Filter) filterList.get(i)).bits(reader));
092: }
093: return bits;
094: }
095: //There are no filters defined. In this case, we return a new
096: //BitSet that will filter out all documents. This is probably the most
097: //consistent behavior with the Lucene API. It's also a lot more
098: //efficient considering the BitSet implementation.
099: else {
100: return new BitSet(reader.maxDoc());
101: }
102: }
103: }
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