Java如何读取Oracle大字段数据

public String clobToString(Clob c) {
    StringBuffer sb = new StringBuffer(1024);
    Reader instream = null;
    try {
      instream = c.getCharacterStream();
      char[] buffer = new char[(int) c.length()];
      int length = 0;
      while ((length = instream.read(buffer)) != -1) {
        sb.append(buffer, 0, length); 
      }
    } catch (Exception ex) {
      ex.printStackTrace();
      return null;
    } finally {
      try {
        if (instream != null)
          instream.close();
      } catch (Exception dx) {
        instream = null;
      }
    }
    return sb.toString();
  }

if(pageObject.getResultList() != null && pageObject.getResultList().size() > 0){
      for(int i=0,j=pageObject.getResultList().size(); i < j;i++){
        Map<String,Object> maps = (Map<String, Object>) pageObject.getResultList().get(i);
        maps.put("DISPATCHINGRULESNAME",this.clobToString((Clob) maps.get("DISPATCHINGRULESNAME"))); //这里将Clob类型转化成字符串,调用clobToString((Clob)方法
      }
    }