由于项目需要用到Lucene，所以决定这个周末学一下Lucene，Lucene最新的版本是5.3.0。下载5.3.0后发现有点坑，文档的例子好像有点旧。
下面是文档中的代码片段，但是5.3.0的FSDirectory.open()参数是Path类型的，而不是String类型的。
1 Analyzer analyzer = new StandardAnalyzer();
2
3 // Store the index in memory:
4 Directory directory = new RAMDirectory();
5 // To store an index on disk, use this instead:
6 //Directory directory = FSDirectory.open("/tmp/testindex");
7 IndexWriterConfig cOnfig= new IndexWriterConfig(analyzer);
8 IndexWriter iwriter = new IndexWriter(directory, config);
9 Document doc = new Document();
10 String text = "This is the text to be indexed.";
11 doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
12 iwriter.addDocument(doc);
13 iwriter.close();
14
15 // Now search the index:
16 DirectoryReader ireader = DirectoryReader.open(directory);
17 IndexSearcher isearcher = new IndexSearcher(ireader);
18 // Parse a simple query that searches for "text":
19 QueryParser parser = new QueryParser("fieldname", analyzer);
20 Query query = parser.parse("text");
21 ScoreDoc[] hits = isearcher.search(query, null, 1000).scoreDocs;
22 assertEquals(1, hits.length);
23 // Iterate through the results:
24 for (int i = 0; i ) {
25 Document hitDoc = isearcher.doc(hits[i].doc);
26 assertEquals("This is the text to be indexed.", hitDoc.get("fieldname"));
27 }
28 ireader.close();
29 directory.close();
我个人不太喜欢接触最新版本的东西，最新的东西一般网上的资料都很少，这会给学习带来不少麻烦，但是在Apache官网找了很久没找到旧版本的，所以也只能学5.3.0。
下面是根据文档自己编写的一个小DEMO（以书为例子创建索引库）。
整个目录的结构如下：
这里我对经常用到的代码进行了提取，创建了两个工具类：IndexUtil（提供indexWriter和indexSearcher），BookDocUtil（实现Book实体和Document对象的转化）。
1、IndexUtil.java
1 package util;
2
3 import java.nio.file.Paths;
4 import org.apache.lucene.analysis.Analyzer;
5 import org.apache.lucene.analysis.standard.StandardAnalyzer;
6 import org.apache.lucene.index.DirectoryReader;
7 import org.apache.lucene.index.IndexWriter;
8 import org.apache.lucene.index.IndexWriterConfig;
9 import org.apache.lucene.search.IndexSearcher;
10 import org.apache.lucene.store.Directory;
11 import org.apache.lucene.store.FSDirectory;
12
13 public class IndexUtil {
14
15 private static final String INDEX_DIR = "./index";
16 private static IndexWriter iWriter;
17 private static IndexSearcher iSearcher;
18
19 private IndexUtil(){}
20
21 public static IndexWriter getIndexWriter() {
22 try {
23 Directory dir = FSDirectory.open(Paths.get(INDEX_DIR));
24 Analyzer analyzer = new StandardAnalyzer();
25 IndexWriterConfig iwc = new IndexWriterConfig(analyzer);
26 iWriter = new IndexWriter(dir, iwc);
27 } catch (Exception e) {
28 throw new RuntimeException(e);
29 }
30 return iWriter;
31 }
32
33 public static IndexSearcher getIndexSearcher() {
34 try {
35 Directory dir = FSDirectory.open(Paths.get(INDEX_DIR));
36 DirectoryReader dirReader = DirectoryReader.open(dir);
37 iSearcher = new IndexSearcher(dirReader);
38 } catch (Exception e) {
39 throw new RuntimeException(e);
40 }
41 return iSearcher;
42 }
43 }
2、BookDocUtil.java
1 package util;
2
3 import org.apache.lucene.document.Document;
4 import org.apache.lucene.document.Field;
5 import org.apache.lucene.document.Field.Index;
6 import org.apache.lucene.document.Field.Store;
7
8 import entity.Book;
9
10 public class BookDocUtil {
11
12 private BookDocUtil(){}
13
14 public static Document book2Doc(Book book) {
15 Document doc = new Document();
16 Field field = null;
17 field = new Field("id", book.getId().toString(), Store.YES, Index.NOT_ANALYZED);
18 doc.add(field);
19 field = new Field("isbn", book.getIsbn(), Store.YES, Index.NO);
20 doc.add(field);
21 field = new Field("name", book.getName(), Store.YES, Index.ANALYZED);
22 doc.add(field);
23 field = new Field("author", book.getAuthor(), Store.YES, Index.NO);
24 doc.add(field);
25 field = new Field("introduction", book.getIntroduction(), Store.YES, Index.ANALYZED);
26 doc.add(field);
27 return doc;
28 }
29
30 public static Book doc2Book(Document doc) {
31 Book book = new Book();
32 book.setId(Integer.parseInt(doc.get("id")));
33 book.setIsbn(doc.get("isbn"));
34 book.setName(doc.get("name"));
35 book.setAuthor(doc.get("author"));
36 book.setIntroduction(doc.get("introduction"));
37 return book;
38 }
39 }
这里我是以书为例子，下面是书的实体类，为了便于打印，这里重写了toString()方法。
3、Book.java
1 package entity;
2
3 public class Book {
4
5 private Integer id;
6 private String isbn;
7 private String name;
8 private String author;
9 private String introduction;
10
11 // 这里省略了setter , getter
12
13 @Override
14 public String toString() {
15 return new StringBuffer()
16 .append("#id : " + this.id)
17 .append("\t#isbn : " + this.isbn)
18 .append("\t#name : " + this.name)
19 .append("\t#author : " + this.author)
20 .append("\tintroducation : " + this.introduction)
21 .toString();
22 }
23 }
第一次接触Lucene，仅仅在BookLuenceService中实现了两个功能 save()、query()。
4、BookLuceneService.java
1 package lucene;
2
3 import java.io.IOException;
4 import java.util.ArrayList;
5 import java.util.List;
6
7 import org.apache.lucene.document.Document;
8 import org.apache.lucene.index.IndexWriter;
9 import org.apache.lucene.index.Term;
10 import org.apache.lucene.search.IndexSearcher;
11 import org.apache.lucene.search.ScoreDoc;
12 import org.apache.lucene.search.TermQuery;
13 import org.apache.lucene.search.TopDocs;
14
15 import entity.Book;
16 import util.BookDocUtil;
17 import util.IndexUtil;
18
19 public class BookLuceneService {
20
21 private boolean debug = false;
22
23 public BookLuceneService(boolean debug) {
24 this.debug = debug;
25 }
26
27 public void save( Book book ) {
28 IndexWriter iWriter = IndexUtil.getIndexWriter();
29 try {
30 iWriter.addDocument(BookDocUtil.book2Doc(book));
31 } catch (IOException e) {
32 throw new RuntimeException(e);
33 } finally {
34 try {
35 iWriter.close();
36 } catch (IOException e) {
37 throw new RuntimeException(e);
38 }
39 }
40 }
41
42 public List query(Integer id) {
43 List bookList = new ArrayList();
44 IndexSearcher iSearcher = IndexUtil.getIndexSearcher();
45 try {
46 TopDocs topDocs = iSearcher.search(new TermQuery(new Term("id", id.toString())), 10);
47 ScoreDoc []scoreDocs = topDocs.scoreDocs;
48
49 ScoreDoc sTemp = null;
50 Document doc = null;
51 for (int i = 0; i ) {
52 sTemp = scoreDocs[i];
53 //-----debug info-----------
54 if (debug) System.err.println("doc : " + sTemp.doc + "\tscore : " + sTemp.score);
55 //--------------------------
56 doc = iSearcher.doc(sTemp.doc);
57 bookList.add(BookDocUtil.doc2Book(doc));
58 }
59
60 } catch (IOException e) {
61 throw new RuntimeException(e);
62 }
63 return bookList;
64 }
65
66 }
最后创建一个测试类对这两个功能进行测试（ 首先运行testSave()创建索引，然后运行testQuery()进行查询 ）：
5、_Test_BookLuceneService.java
1 package test;
2
3 import org.junit.AfterClass;
4 import org.junit.BeforeClass;
5 import org.junit.Test;
6
7 import entity.Book;
8 import lucene.BookLuceneService;
9
10 public class _Test_BookLuceneService {
11
12 private static BookLuceneService bookLuceneService;
13
14 @BeforeClass
15 public static void init() {
16 bookLuceneService = new BookLuceneService(true);
17 }
18
19
20 // @Test
21 public void testSave() {
22
23 Book book = new Book();
24 book.setId(1);
25 book.setIsbn("978-7-121-21732-6");
26 book.setName("Hello World");
27 book.setAuthor("ITC10");
28 book.setIntroduction("Say hello world to every language.");
29
30 bookLuceneService.save(book);
31 }
32
33 @Test
34 public void testQuery() {
35
36 for( Book book : bookLuceneService.query(1)) {
37 System.out.println(book.toString());
38 }
39 }
40
41 @AfterClass
42 public static void destroy () {
43 bookLuceneService = null;
44 }
45 }
测试testQuery()结果如下：
1 doc : 0 score : 0.30685282
2 #id : 1 #isbn : 978-7-121-21732-6 #name : Hello World #author : ITC10 introducation : Say hello world to every language.
这里可以刷新项目工程目录，会发现多了一个index目录，这就是索引库的位置。
。
第一次学Lucene还得继续慢慢摸索。
Lucene 初学-5.3.0
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