Java tutorial
/* * Copyright (C) 2013 lichtflut Forschungs- und Entwicklungsgesellschaft mbH * * Licensed 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.arastreju.sge.spi.impl; import org.apache.lucene.analysis.standard.StandardAnalyzer; import org.apache.lucene.document.Document; import org.apache.lucene.document.Field; import org.apache.lucene.document.NumericField; import org.apache.lucene.index.IndexReader; import org.apache.lucene.index.IndexWriter; import org.apache.lucene.index.IndexWriterConfig; import org.apache.lucene.index.Term; import org.apache.lucene.search.IndexSearcher; import org.apache.lucene.search.TermQuery; import org.apache.lucene.search.TopDocs; import org.apache.lucene.store.Directory; import org.apache.lucene.store.FSDirectory; import org.apache.lucene.util.Version; import org.arastreju.sge.naming.QualifiedName; import org.arastreju.sge.persistence.NodeKeyTable; import org.arastreju.sge.spi.PhysicalNodeID; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.File; import java.io.IOException; /** * <p> * Node key table based on a lucene index. * </p> * * <p> * Created Mar 22, 2013 * </p> * * @author Oliver Tigges */ public abstract class LuceneBasedNodeKeyTable<T extends PhysicalNodeID> implements NodeKeyTable<T> { private static final Logger LOGGER = LoggerFactory.getLogger(LuceneBasedNodeKeyTable.class); public static final String PID = "pid"; public static final String QN = "qn"; // ---------------------------------------------------- private final Directory dir; private final IndexWriter writer; // ---------------------------------------------------- public static LuceneBasedNodeKeyTable<NumericPhysicalNodeID> forNumericIDs(String baseDir) throws IOException { return new LuceneBasedNodeKeyTable<NumericPhysicalNodeID>(baseDir) { @Override protected NumericPhysicalNodeID createID(Document doc) { NumericField field = (NumericField) doc.getFieldable(PID); return new NumericPhysicalNodeID(field.getNumericValue()); } @Override protected void setID(Document doc, NumericPhysicalNodeID id) { NumericField field = new NumericField(PID, Field.Store.YES, false); field.setLongValue(id.asLong()); doc.add(field); } }; } // ---------------------------------------------------- protected LuceneBasedNodeKeyTable(String baseDir) throws IOException { final File indexDir = new File(baseDir, "__qn_index"); LOGGER.info("Creating node key table index in {}.", indexDir); boolean created = indexDir.mkdir(); IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_35, new StandardAnalyzer(Version.LUCENE_35)); this.dir = FSDirectory.open(indexDir); this.writer = new IndexWriter(dir, config); if (created) { LOGGER.info("Index directory newly created. Starting initialization."); writer().commit(); } } // ---------------------------------------------------- @Override public T lookup(QualifiedName qualifiedName) { TermQuery query = new TermQuery(new Term(QN, qualifiedName.toURI())); IndexReader reader = reader(); try { IndexSearcher searcher = new IndexSearcher(reader); TopDocs result = searcher.search(query, 2); searcher.close(); if (result.scoreDocs.length == 1) { Document document = reader.document(result.scoreDocs[0].doc); return createID(document); } else if (result.scoreDocs.length == 0) { return null; } else { throw new IllegalStateException( "Found more than one document for qualified name: " + qualifiedName); } } catch (IOException e) { throw new RuntimeException("Could not query by qualified name.", e); } finally { try { reader.close(); } catch (IOException e) { throw new RuntimeException("Could not close index reader.", e); } } } @Override public synchronized void put(QualifiedName qn, T physicalID) { Document doc = new Document(); doc.add(new Field(QN, qn.toURI(), Field.Store.YES, Field.Index.NOT_ANALYZED)); setID(doc, physicalID); try { final IndexWriter writer = writer(); writer.addDocument(doc); writer.commit(); } catch (IOException e) { throw new RuntimeException("Could not map phyiscal ID to qualified name in index.", e); } } @Override public void remove(QualifiedName qn) { try { final IndexWriter writer = writer(); writer.deleteDocuments(new Term(QN, qn.toURI())); writer.commit(); } catch (IOException e) { throw new RuntimeException("Could not remove qualified name from index.", e); } } @Override public void shutdown() throws IOException { writer.close(); dir.close(); } // ---------------------------------------------------- protected abstract T createID(Document doc); protected abstract void setID(Document doc, T id); // ---------------------------------------------------- private IndexReader reader() { try { return IndexReader.open(dir, true); } catch (IOException e) { throw new RuntimeException("Unable to obtain an index reader.", e); } } private IndexWriter writer() throws IOException { return writer; } }