code: public boolean isIndexed() {
          if( indexes == null ){
              InputStream stream = null;
              try {
                  stream = getInputStream("META-INF/INDEX.DETAIL");
                  List<String> lines = IOUtils.readLines(stream);
                  //是否应该讲indexes hash化？
                  indexes = lines.toArray(new String[lines.size()]);
                  // to be quick searched
                  Arrays.sort(indexes);
              } catch (Exception e) {
                  indexes = new String[0];
              } finally {
                  IOUtils.closeQuietly(stream);
              }
          }
          return indexes.length > 0 ;
      }
docs: 判断本组件包是否被索引
  
  @return 存在META-INF/INDEX.DETAIL 文件即为被索引