权值

【概述】

在数学领域，权值指加权平均数中的每个数的频数，也称为权数或权重。在搜索引擎中，权值越高的内容在排序中越靠前。

实际应用中可以通过修改权值来重新调整索引在列表中的排序位置。

【示例】

    /**
     * 创建索引
     */
    @Test
    public void testIndex(){
        //存储3篇文章的信息。包括：id、标题、作者、内容
        int[] ids = {1,2,3};
        String[] titles = {"Hello","I love you","morning"};
        String[] authors = {"Hello Mike","HanMeimei","Tom"};
        String[] contents= {"Hello,My Name Is Mike; good","Tome,I Love You; good，good,good","Good Moring,I'm so sorry; good,，good,good，good,good"};
        
        IndexWriter writer = null;
        
        try {
            //1、创建Directory
            Directory directory = FSDirectory.open(new File("E:\lucene\index2"));
            
            //2、创建Writer
            ......
            
            for(int i = 0;i<ids.length;i++){
                doc = new Document();
                
                //为文档添加域(属性)
                String id = Integer.toString(ids[i]);
                doc.add(new Field("id",id,Field.Store.YES,Field.Index.NOT_ANALYZED_NO_NORMS));
                doc.add(new Field("title",titles[i],Field.Store.YES,Field.Index.NOT_ANALYZED));
                doc.add(new Field("author",authors[i],Field.Store.YES,Field.Index.NOT_ANALYZED));
                doc.add(new Field("content", contents[i],Field.Store.NO,Field.Index.ANALYZED));
                
                //修改索引的权值
                //默认权值为1.0
                //将Id为1的数据权值调整到5.0
                if(ids[i] == 1)
                    doc.setBoost(5.0f);
                
                writer.addDocument(doc);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        finally{
            if(writer != null)
                try {
                    writer.close();
                } catch (CorruptIndexException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
        }
    }

注意：读取索引时读取到的权值和索引中的权值是不同的。因为他们属于不同的doc对象。