Jforum中索引模块的分析(1)

 较早的时候分析过Jforum中的lucene索引模块，当时觉得代码真是短小精悍！值得学习。

1.SearchManager接口，

  JForum定义了一个SearchManager接口，通过LuceneManager实现了其中的方法。对于索引和检索进行统一的管理。

public class LuceneManager implements SearchManager { private LuceneSearch search; private LuceneSettings settings; private LuceneIndexer indexer; /** * @see net.jforum.search.SearchManager#init() */ public void init() { try { /*读取配置文件，初始化解析器*/ Analyzer analyzer = (Analyzer)Class.forName(SystemGlobals.getValue( ConfigKeys.LUCENE_ANALYZER)).newInstance(); this.settings = new LuceneSettings(analyzer); /*设定索引存放的目录*/ this.settings.useFSDirectory(SystemGlobals.getValue(ConfigKeys.LUCENE_INDEX_WRITE_PATH)); this.removeLockFile(); this.indexer = new LuceneIndexer(this.settings); this.search = new LuceneSearch(this.settings, new LuceneContentCollector(this.settings)); /*将LuceneSearch对象作为参数传入，当新的POST提交以后， *建立索引，LuceneSearch关闭索引文件，然后重新打开。*/ this.indexer.watchNewDocuDocumentAdded(this.search); SystemGlobals.setObjectValue(ConfigKeys.LUCENE_SETTINGS, this.settings); } catch (Exception e) { throw new ForumException(e); } }

其余的是，针对POST的create、delete、update索引方法。

2.LuceneIndexer类

   主要是对POST建立索引，主要方法有：

   2.1 create(Post post)

  public void create(Post post) { synchronized (MUTEX) { IndexWriter writer = null; try { writer = new IndexWriter(this.settings.directory(), this.settings.analyzer()); Document document = this.createDocument(post); writer.addDocument(document); this.optimize(writer); if (logger.isDebugEnabled()) { logger.debug("Indexed " + document); } } catch (Exception e) { logger.error(e.toString(), e); } finally { if (writer != null) { try { writer.flush(); writer.close(); this.notifyNewDocumentAdded(); } catch (Exception e) {} } } } } 

  新建一个Lucene中的IndexWriter，通过createDocument方法对于POST进行索引，关闭writer，调用notifyNewDocumentAdded()方法

告知IndexSearch索引已经更新，需要重新的打开。

  2.2 createDocument(Post)方法

  new Field(SearchFields.Keyword.USER_ID, String.valueOf(p.getUserId()), Store.YES, Index.UN_TOKENIZED)); d.add(new Field(SearchFields.Keyword.DATE, this.settings.formatDateTime(p.getTime()), Store.YES, Index.UN_TOKENIZED)); // We add the subject and message text together because, when searching, we only care about the // matches, not where it was performed. The real subject and contents will be fetched from the database d.add(new Field(SearchFields.Indexed.CONTENTS, p.getSubject() + " " + p.getText(), Store.NO, Index.TOKENIZED)); return d; } 

  将POST_ID,FORUM_ID,TOPIC_ID,USER_ID,文章内容进行索引。

  2.3 Update(Post)方法

  更新Post之后，重新建立索引。

  public void update(Post post) { if (this.performDelete(post)) { this.create(post); } } private boolean performDelete(Post p) { synchronized (MUTEX) { IndexReader reader = null; boolean status = false; try { reader = IndexReader.open(this.settings.directory()); reader.deleteDocuments(new Term(SearchFields.Keyword.POST_ID, String.valueOf(p.getId()))); status = true; } catch (IOException e) { logger.error(e.toString(), e); } finally { if (reader != null) { try { reader.close(); } catch (Exception e) {} } } return status; } } 

  首先删除该Post的索引，通过POST_ID，然后重新建立索引。

  2.4 notifyNewDocumentAdded方法

  在建立索引或者重新建立索引之后，都调用notifyNewDocumentAdded通知IndexSearch，索引文件已经更新，需要重新载入。

 

 private void notifyNewDocumentAdded() { for (Iterator iter = this.newDocumentAddedList.iterator(); iter.hasNext(); ) { ((NewDocumentAdded)iter.next()).newDocumentAdded(); } }

 其中LuceneSearch实现了NewDocumentAdded接口。

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 public void newDocumentAdded() { try { this.search.close(); this.openSearch(); } catch (Exception e) { throw new SearchException(e); } } 

 重新打开索引文件。

3.索引总结

  结构很清晰，就是提交POST或者更新POST之后，重新打开索引文件。