Lucene 4 和 Solr 4 学习笔记(3)

    当初说要写写lucene和solr的学习笔记，写了两个后就懒得写了。最近想做个lucene和solr的中文学习网站，翻译一些lucene和solr的英文资料，并提供一个中文的交流学习平台。所以想把这个系列继续下去。

    言归正传，上面说到我们的目标是学习和修改lucene/solr的源代码。不过如果我们从没有用过，那是不可能读懂源代码的。这里推荐《lucene in action》第二版，中文版也有，网上能够下载到英文版的，建议阅读英文版。这本书的第一作者Michael McCandless是现在Lucene PMC的成员，他的blog可以关注一下

http://blog.mikemccandless.com，另外两个作者是本书第一版的作者，好像现在在lucene和solr的开发中不是特别活跃，在lucene和solr的邮件列表中没怎么见过。

   下面我们简单的学习（或者复习）一下Lucene的建索引过程，我们将给出lucene 2.x/3.x 和 最新trunk正在开发的4.0的建立索引的方法，尤其是它们的区别。

    Lucene 2.x/3.x里建立索引并进行简单搜索的例子

	Directory dir=FSDirectory.open(new File("./testindex"));
	for(String fn:dir.listAll()){
	    dir.deleteFile(fn);
	}
	IndexWriter writer=new IndexWriter(dir,new WhitespaceAnalyzer(Version.LUCENE_36),IndexWriter.MaxFieldLength.UNLIMITED);

	Document doc=new Document();
	doc.add(new Field("id","0001",Field.Store.YES,Field.Index.NOT_ANALYZED));
        doc.add(new Field("body","hello world, this is text body part. ",Field.Store.NO,Field.Index.ANALYZED));
        doc.add(new Field("clickCount","10",Field.Store.YES,Field.Index.NO));
        writer.addDocument(doc);
	    
        doc=new Document();
	doc.add(new Field("id","0002",Field.Store.YES,Field.Index.NOT_ANALYZED));
        doc.add(new Field("body","good bye. that is it. ",Field.Store.NO,Field.Index.ANALYZED));
	doc.add(new Field("clickCount","3",Field.Store.YES,Field.Index.NO));
	writer.addDocument(doc);
	    
	writer.close();
	    
	IndexReader reader=IndexReader.open(dir);
	IndexSearcher searcher=new IndexSearcher(reader);
	Query q=new TermQuery(new Term("body","is"));
	TopDocs docs=searcher.search(q, 10);
	for(int i=0;i<docs.totalHits;i++){
	      int docId=docs.scoreDocs[i].doc;
	      float score=docs.scoreDocs[i].score;
	      doc=searcher.doc(docId);

	      System.out.println("id="+doc.get("id")+", clickcount="+doc.get("clickCount"));
	}
	reader.close();

   

Lucene 4 里建立索引并进行简单搜索的例子

    Directory dir=FSDirectory.open(new File("./testindex"));
    IndexWriterConfig cfg=new IndexWriterConfig(Version.LUCENE_40,new WhitespaceAnalyzer(Version.LUCENE_40));
    cfg.setOpenMode(OpenMode.CREATE);
    IndexWriter writer=new IndexWriter(dir,cfg);
    Document doc=new Document();
    doc.add(new Field("id","0001",StringField.TYPE_STORED));
    doc.add(new TextField("body","hello world, this is text body part. "));
    doc.add(new DocValuesField("clickcount",10,DocValues.Type.FIXED_INTS_8));
    writer.addDocument(doc);
    
    doc=new Document();
    doc.add(new Field("id","0002",StringField.TYPE_STORED));
    doc.add(new TextField("body","good bye. that is it. "));
    doc.add(new DocValuesField("clickcount",3,DocValues.Type.FIXED_INTS_8));
    writer.addDocument(doc);
    
    writer.close();
    
    IndexReader reader=DirectoryReader.open(dir);
    IndexSearcher searcher=new IndexSearcher(reader);
    Query q=new TermQuery(new Term("body","is"));
    TopDocs docs=searcher.search(q, 10);
    DocValues docValues = MultiDocValues.getDocValues(reader, "clickcount");
    Source source = docValues.getSource();
    for(int i=0;i<docs.totalHits;i++){
      int docId=docs.scoreDocs[i].doc;