Lucene4.3进阶开发之柳暗花明( 六)
转载请务必注明，原创地址，谢谢配合!
http://qindongliang1922.iteye.com/blog/1999154


上篇文章，散仙介绍了IndexWriter的作用，它的最大价值体现在对索引的创建，管理和维护上，通过与IndexWriterConfig这个配置管理类的组合，可以实现最佳的索引策略，当然前提是你得了解IndexWriterConfig里一些重要的参数的配置含义。


本篇文章散仙要介绍的是IndexSearcher这个类，这个类是Lucene在进行检索时必不可少的一个组件，可以称为是检索的入口，通过这个入口之后，我们就可以获取与我们检索的关键词相关的一系列Doc，然后我们就可以进行后续相关的业务处理。

所以我们经常会在代码里这样写：

  private static final class SearcherCallableNoSort implements Callable<TopDocs> {    private final Lock lock;    private final IndexSearcher searcher;    private final Weight weight;    private final ScoreDoc after;    private final int nDocs;    private final HitQueue hq;    private final LeafSlice slice;    public SearcherCallableNoSort(Lock lock, IndexSearcher searcher, LeafSlice slice,  Weight weight,        ScoreDoc after, int nDocs, HitQueue hq) {      this.lock = lock;      this.searcher = searcher;      this.weight = weight;      this.after = after;      this.nDocs = nDocs;      this.hq = hq;      this.slice = slice;    }    @Override    public TopDocs call() throws IOException {      final TopDocs docs = searcher.search(Arrays.asList(slice.leaves), weight, after, nDocs);      final ScoreDoc[] scoreDocs = docs.scoreDocs;      //it would be so nice if we had a thread-safe insert       lock.lock();      try {        for (int j = 0; j < scoreDocs.length; j++) { // merge scoreDocs into hq          final ScoreDoc scoreDoc = scoreDocs[j];          if (scoreDoc == hq.insertWithOverflow(scoreDoc)) {            break;          }        }      } finally {        lock.unlock();      }      return docs;    }  }