Lucene 高亮显示

Lucene高亮显示
public static List search(String[] fields, String keyword)
throws IOException, InvalidTokenOffsetsException {

ArrayList list = new ArrayList();
IndexSearcher isearcher = null;

IKSimilarity iKSimilarity = new IKSimilarity();

Directory dir = new SimpleFSDirectory(new File(indexDir));

IndexReader indexReader = IndexReader.open(dir, true);

isearcher = new IndexSearcher(indexReader);

Analyzer analyzer = new IKAnalyzer();

isearcher.setSimilarity(iKSimilarity);

// QueryParser parser = new
// QueryParser(Version.LUCENE_30,field,analyzer);

Query query = IKQueryParser.parseMultiField(fields, keyword);

TopScoreDocCollector collector = TopScoreDocCollector.create(100, false);

isearcher.search(query, collector);

// TopDocs topDocs = isearcher.search(query , 5);

TopDocs topDocs = collector.topDocs();

ScoreDoc[] scoreDocs = topDocs.scoreDocs;

for (int i = 0; i < scoreDocs.length; i++) {
Document doc = isearcher.doc(scoreDocs[i].doc);

/** 高亮显示的关键步骤 **/
SimpleHTMLFormatter simpleHtmlFormatter = new SimpleHTMLFormatter("<font color='red'>","</font>");
Highlighter highlighter = new Highlighter(simpleHtmlFormatter,new QueryScorer(query));
highlighter.setTextFragmenter(new SimpleFragmenter(50));
String goal= doc.get("goal");
String highlightGoal = "";
if(!goal.equals("")){
    TokenStream tokenStream = analyzer.tokenStream("goal",new StringReader(goal));
    highlightGoal = highlighter.getBestFragment(tokenStream, goal); 
   /** 注意 ***/

    if(highlightGoal==null){
        highlightGoal = goal;
   }
}

/** 封装高亮信息 **/
Info info = new Info();
info.setNo(doc.getField("no").stringValue());
info.setWeight(isearcher.explain(query, scoreDocs[i].doc).getValue());
info.setGoal(highlightGoal);
list.add(info);
}
return list;
}

 

在做这个例子的过程中遇到了一个问题，出现在

if(highlightGoal==null){
        highlightGoal = goal;
   }
如果goal中没有关键词 词元，highlightGoal就会为null