indexWriter.updateDocument(new Term("url", "http://www.lietu.com"), document);

        public void searchAndUpdateDocument(IndexWriter writer,
                                        IndexSearcher searcher,
                                        Document updateDoc,
                                        Term term) throws IOException {
              TermQuery query = new TermQuery(term);


              TopDocs hits = searcher.search(query, 10);


              if (hits.scoreDocs.length == 0) {
                      throw new IllegalArgumentException("索引中沒有匹配的結果");
              } else if (hits.scoreDocs.length > 1) {
                      throw new IllegalArgumentException("Given Term matches
                        more than 1 document in the index.");
              } else {
                      int docId = hits.scoreDocs[0].doc;


                      //找出舊的文檔
                      Document doc = searcher.doc(docId);


                      List<Field> replacementFields = updateDoc.getFields();
                      for (Field field : replacementFields) {
                            String name = field.name();
                            String currentValue = doc.get(name);
                            if (currentValue ! = null) {
                                  //替換列值
                                  Field = new Field(name, term.text());
                                  //刪除所有出現的值舊列
                                  doc.removeFields(name);


                                  //插入替換列
                                  doc.add(field);
                            } else {
                                  //新加到列
                                  doc.add(field);
                            }
                    }


                    //把舊文檔更改后重新寫入索引
                    writer.updateDocument(term, doc);
              }
      }