用lucene为数据库搜索建立增量索引

用lucene为数据库搜索建立增量索引 用 lucene 建立索引不可能每次都重新开始建立,而是按照新增加的记录,一次次的递增
建立索引的IndexWriter类,有三个参数


IndexWriter writer = new IndexWriter(path, new StandardAnalyzer(),isEmpty);
其中第三个参数是bool型的,指定它可以确定是增量索引,还是重建索引.
对于从数据库中读取的记录,譬如要为文章建立索引,我们可以记录文章的id号,然后下次再次建立索引的时候读取存下的id号,从此id后往下继续增加索引,逻辑如下.

建立增量索引,主要代码如下
public void createIndex(String path)
{
     Statement myStatement = null;
     String articleId="0";
     //读取文件,获得文章id号码,这里只存最后一篇索引的文章id
    try {
        FileReader fr = new FileReader("**.txt");
        BufferedReader br = new BufferedReader(fr);                
        articleId=br.readLine();
        if(articleId==null||articleId=="")
        articleId="0";
        br.close();
        fr.close();
      } catch (IOException e) {
        System.out.println("error343!");
        e.printStackTrace();
      }
    try {
        //sql语句,根据id读取下面的内容
        String sqlText = "*****"+articleId;
        myStatement = conn.createStatement();
        ResultSet rs = myStatement.executeQuery(sqlText);
       //写索引
        while (rs.next()) {
         Document doc = new Document();
         doc.add(Field.Keyword("**", DateAdded));
         doc.add(Field.Keyword("**", articleid));
         doc.add(Field.Text("**", URL));   
         doc.add(Field.Text("**", Content));
         doc.add(Field.Text("**", Title));   
         try{
            writer.addDocument(doc);
          }
          catch(IOException e){
            e.printStackTrace();
         }
           //将我索引的最后一篇文章的id写入文件
          try {
           FileWriter fw = new FileWriter("**.txt");
           PrintWriter out = new PrintWriter(fw);   
           out.close();
           fw.close();
           } catch (IOException e) {
             e.printStackTrace();
           }
         }
            ind.Close();
            System.out.println("ok.end");
         }
         catch (SQLException e){
            e.printStackTrace();
        }
        finally {
            //数据库关闭操作
        }       
    }

然后控制是都建立增量索引的时候根据能否都到id值来设置IndexWriter的第三个参数为true 或者是false

boolean isEmpty = true;
try {
    FileReader fr = new FileReader("**.txt");
    BufferedReader br = new BufferedReader(fr);                
    if(br.readLine()!= null) {
        isEmpty = false;
     }
     br.close();
     fr.close();
    } catch (IOException e) {
       e.printStackTrace();
  }
           
  writer = new IndexWriter(Directory, new StandardAnalyzer(),isEmpty);