Java tutorial
/* * 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.search; import java.io.IOException; import org.apache.lucene.index.Term; import org.apache.lucene.index.Terms; import org.apache.lucene.index.TermsEnum; import org.apache.lucene.util.Accountable; import org.apache.lucene.util.AttributeSource; import org.apache.lucene.util.RamUsageEstimator; import org.apache.lucene.util.automaton.Automaton; import org.apache.lucene.util.automaton.CompiledAutomaton; import org.apache.lucene.util.automaton.Operations; /** * A {@link Query} that will match terms against a finite-state machine. * <p> * This query will match documents that contain terms accepted by a given * finite-state machine. The automaton can be constructed with the * {@link org.apache.lucene.util.automaton} API. Alternatively, it can be * created from a regular expression with {@link RegexpQuery} or from * the standard Lucene wildcard syntax with {@link WildcardQuery}. * </p> * <p> * When the query is executed, it will create an equivalent DFA of the * finite-state machine, and will enumerate the term dictionary in an * intelligent way to reduce the number of comparisons. For example: the regular * expression of <code>[dl]og?</code> will make approximately four comparisons: * do, dog, lo, and log. * </p> * @lucene.experimental */ public class AutomatonQuery extends MultiTermQuery implements Accountable { private static final long BASE_RAM_BYTES = RamUsageEstimator.shallowSizeOfInstance(AutomatonQuery.class); /** the automaton to match index terms against */ protected final Automaton automaton; protected final CompiledAutomaton compiled; /** term containing the field, and possibly some pattern structure */ protected final Term term; protected final boolean automatonIsBinary; private final long ramBytesUsed; // cache /** * Create a new AutomatonQuery from an {@link Automaton}. * * @param term Term containing field and possibly some pattern structure. The * term text is ignored. * @param automaton Automaton to run, terms that are accepted are considered a * match. */ public AutomatonQuery(final Term term, Automaton automaton) { this(term, automaton, Operations.DEFAULT_MAX_DETERMINIZED_STATES); } /** * Create a new AutomatonQuery from an {@link Automaton}. * * @param term Term containing field and possibly some pattern structure. The * term text is ignored. * @param automaton Automaton to run, terms that are accepted are considered a * match. * @param maxDeterminizedStates maximum number of states in the resulting * automata. If the automata would need more than this many states * TooComplextToDeterminizeException is thrown. Higher number require more * space but can process more complex automata. */ public AutomatonQuery(final Term term, Automaton automaton, int maxDeterminizedStates) { this(term, automaton, maxDeterminizedStates, false); } /** * Create a new AutomatonQuery from an {@link Automaton}. * * @param term Term containing field and possibly some pattern structure. The * term text is ignored. * @param automaton Automaton to run, terms that are accepted are considered a * match. * @param maxDeterminizedStates maximum number of states in the resulting * automata. If the automata would need more than this many states * TooComplextToDeterminizeException is thrown. Higher number require more * space but can process more complex automata. * @param isBinary if true, this automaton is already binary and * will not go through the UTF32ToUTF8 conversion */ public AutomatonQuery(final Term term, Automaton automaton, int maxDeterminizedStates, boolean isBinary) { super(term.field()); this.term = term; this.automaton = automaton; this.automatonIsBinary = isBinary; // TODO: we could take isFinite too, to save a bit of CPU in CompiledAutomaton ctor?: this.compiled = new CompiledAutomaton(automaton, null, true, maxDeterminizedStates, isBinary); this.ramBytesUsed = BASE_RAM_BYTES + term.ramBytesUsed() + automaton.ramBytesUsed() + compiled.ramBytesUsed(); } @Override protected TermsEnum getTermsEnum(Terms terms, AttributeSource atts) throws IOException { return compiled.getTermsEnum(terms); } @Override public int hashCode() { final int prime = 31; int result = super.hashCode(); result = prime * result + compiled.hashCode(); result = prime * result + ((term == null) ? 0 : term.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (!super.equals(obj)) return false; if (getClass() != obj.getClass()) return false; AutomatonQuery other = (AutomatonQuery) obj; if (!compiled.equals(other.compiled)) return false; if (term == null) { if (other.term != null) return false; } else if (!term.equals(other.term)) return false; return true; } @Override public String toString(String field) { StringBuilder buffer = new StringBuilder(); if (!term.field().equals(field)) { buffer.append(term.field()); buffer.append(":"); } buffer.append(getClass().getSimpleName()); buffer.append(" {"); buffer.append('\n'); buffer.append(automaton.toString()); buffer.append("}"); return buffer.toString(); } @Override public void visit(QueryVisitor visitor) { if (visitor.acceptField(getField())) { visitor.visitLeaf(this); } } /** Returns the automaton used to create this query */ public Automaton getAutomaton() { return automaton; } /** Is this a binary (byte) oriented automaton. See the constructor. */ public boolean isAutomatonBinary() { return automatonIsBinary; } @Override public long ramBytesUsed() { return ramBytesUsed; } }