索引是识别文档并为搜索准备文档的过程。
下表列出了索引过程中常用的类。
类描述IndexWriter在索引过程中创建/更新索引。Directory表示索引的存储位置。Analyzer分析文档并从文本中获取标记/单词。Document带有字段的虚拟文档。分析仪可以处理文档。Field索引过程的最低单位。它表示键值对，其中键用于标识索引值。
例子
以下代码显示了如何使用Lucene索引文本文件。
/*
* 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 org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.LongField;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig.OpenMode;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Date;
/** Index all text files under a directory.
* <p>
* This is a command-line application demonstrating simple Lucene indexing.
* Run it with no command-line arguments for usage information.
*/
public class Main {
private Main() {}
/** Index all text files under a directory. */
public static void main(String[] args) {
String usage = "java IndexFiles"
+ " [-index INDEX_PATH] [-docs DOCS_PATH] [-update]\n\n"
+ "This indexes the documents in DOCS_PATH, creating a Lucene index"
+ "in INDEX_PATH that can be searched with SearchFiles";
String indexPath = "index";
String docsPath = null;
boolean create = true;
for(int i=0;i<args.length;i++) {
if ("-index".equals(args[i])) {
indexPath = args[i+1];
i++;
} else if ("-docs".equals(args[i])) {
docsPath = args[i+1];
i++;
} else if ("-update".equals(args[i])) {
create = false;
}
}
if (docsPath == null) {
System.err.println("Usage: " + usage);
System.exit(1);
}
final File docDir = new File(docsPath);
if (!docDir.exists() || !docDir.canRead()) {
System.out.println("Document directory "" +docDir.getAbsolutePath()+ "" does not exist or is not readable, please check the path");
System.exit(1);
}
Date start = new Date();
try {
System.out.println("Indexing to directory "" + indexPath + ""...");
Directory dir = FSDirectory.open(new File(indexPath));
// :Post-Release-Update-Version.LUCENE_XY:
Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_4_10_0);
IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_4_10_0, analyzer);
if (create) {
// Create a new index in the directory, removing any
// previously indexed documents:
iwc.setOpenMode(OpenMode.CREATE);
} else {
// Add new documents to an existing index:
iwc.setOpenMode(OpenMode.CREATE_OR_APPEND);
}
// Optional: for better indexing performance, if you
// are indexing many documents, increase the RAM
// buffer. But if you do this, increase the max heap
// size to the JVM (eg add -Xmx512m or -Xmx1g):
//
// iwc.setRAMBufferSizeMB(256.0);
IndexWriter writer = new IndexWriter(dir, iwc);
indexDocs(writer, docDir);
// NOTE: if you want to maximize search performance,
// you can optionally call forceMerge here. This can be
// a terribly costly operation, so generally it"s only
// worth it when your index is relatively static (ie
// you"re done adding documents to it):
//
// writer.forceMerge(1);
writer.close();
Date end = new Date();
System.out.println(end.getTime() - start.getTime() + " total milliseconds");
} catch (IOException e) {
System.out.println(" caught a " + e.getClass() +
"\n with message: " + e.getMessage());
}
}
/**
* Indexes the given file using the given writer, or if a directory is given,
* recurses over files and directories found under the given directory.
*
* NOTE: This method indexes one document per input file. This is slow. For good
* throughput, put multiple documents into your input file(s). An example of this is
* in the benchmark module, which can create "line doc" files, one document per line,
* using the
* <a href="../../../../../contrib-benchmark/org/apache/lucene/benchmark/byTask/tasks/WriteLineDocTask.html"
* >WriteLineDocTask</a>.
*
* @param writer Writer to the index where the given file/dir info will be stored
* @param file The file to index, or the directory to recurse into to find files to index
* @throws IOException If there is a low-level I/O error
*/
static void indexDocs(IndexWriter writer, File file)
throws IOException {
// do not try to index files that cannot be read
if (file.canRead()) {
if (file.isDirectory()) {
String[] files = file.list();
// an IO error could occur
if (files != null) {
for (int i = 0; i < files.length; i++) {
indexDocs(writer, new File(file, files[i]));
}
}
} else {
FileInputStream fis;
try {
fis = new FileInputStream(file);
} catch (FileNotFoundException fnfe) {
// at least on windows, some temporary files raise this exception with an "access denied" message
// checking if the file can be read doesn"t help
return;
}
try {
// make a new, empty document
Document doc = new Document();
// Add the path of the file as a field named "path". Use a
// field that is indexed (i.e. searchable), but don"t tokenize
// the field into separate words and don"t index term frequency
// or positional information:
Field pathField = new StringField("path", file.getPath(), Field.Store.YES);
doc.add(pathField);
// Add the last modified date of the file a field named "modified".
// Use a LongField that is indexed (i.e. efficiently filterable with
// NumericRangeFilter). This indexes to milli-second resolution, which
// is often too fine. You could instead create a number based on
// year/month/day/hour/minutes/seconds, down the resolution you require.
// For example the long value 2011021714 would mean
// February 17, 2011, 2-3 PM.
doc.add(new LongField("modified", file.lastModified(), Field.Store.NO));
// Add the contents of the file to a field named "contents". Specify a Reader,
// so that the text of the file is tokenized and indexed, but not stored.
// Note that FileReader expects the file to be in UTF-8 encoding.
// If that"s not the case searching for special characters will fail.
doc.add(new TextField("contents", new BufferedReader(new InputStreamReader(fis, StandardCharsets.UTF_8))));
if (writer.getConfig().getOpenMode() == OpenMode.CREATE) {
// New index, so we just add the document (no old document can be there):
System.out.println("adding " + file);
writer.addDocument(doc);
} else {
// Existing index (an old copy of this document may have been indexed) so
// we use updateDocument instead to replace the old one matching the exact
// path, if present:
System.out.println("updating " + file);
writer.updateDocument(new Term("path", file.getPath()), doc);
}
} finally {
fis.close();
}
}
}
}
}
