MapReduce中使用HTMLunit实现爬虫出现java.lang.NoSuchFieldError: INSTANCE

//主要功能是从hbase中读一条URL执行，很简单的代码：

public static class CrawlReducer
            extends TableReducer<Text, IntWritable, NullWritable>{
            @Override
            protected void reduce(Text key, Iterable<IntWritable> value, Context context)
                     throws IOException, InterruptedException{

                     Put put = new Put(Bytes.toBytes(key.toString()));
                     put.add(Bytes.toBytes("content"), Bytes.toBytes("html"),
                                    Bytes.toBytes(startCrawl(key.toString())));
                     context.write(NullWritable.get(), put);
            }
      }

      public static String startCrawl(String url){
            WebClient webClient = new WebClient(BrowserVersion.CHROME);
            webClient.getOptions().setCssEnabled(false);
            webClient.getOptions().setJavaScriptEnabled(true);
            webClient.getOptions().setThrowExceptionOnScriptError(false);
            webClient.setAjaxController(new NicelyResynchronizingAjaxController());
            webClient.getOptions().setTimeout(5000);

            HtmlPage page = null;
            try {
                     page = webClient.getPage(url);//运行到此就错误、、、、、、、、、、、、、、、、、、、、、、、、、、
                     Thread.sleep(5000);
            } catch (FailingHttpStatusCodeException e1) {
                     e1.printStackTrace();
            } catch (MalformedURLException e1) {
                     e1.printStackTrace();
            } catch (IOException e1) {
                     e1.printStackTrace();
            } catch (Exception e) {
                     e.printStackTrace();
            }
            return page.getPage().asXml();
      }
独立运行都没错，但是把下载网页放入reduce就有错，瞎搞了两天没有解决，真郁闷。求大神告知解决方案，搜了MapReduce有什么主意事项基本没有，都是复制一大推Wordcount例子，无语。。。。。。。。
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