oracle中blob類型的字段在jsp頁面顯示

在項目中，有時會將文本文件、圖片以2進制的方式存入數據庫，對應字段的類型爲blob，通常在jsp頁面操做字符串來處理圖片、文本文件，如何將blob類型轉換成String類型就成了關鍵。

public ActionForward getBulletin(ActionMapping mapping, ActionForm form,HttpServletRequest request, HttpServletResponse response) throws Exception {
	buildAllBulletinType(request);
	String id = request.getParameter("id");
	String titleSub = "";
	String title="";
	String state="";
	String bulletinDate = "";
	List ll = BulletinServiceImpl.getInstance().selForId(id);
        if(ll!=null && ll.size()>0)
	{
             Object [] obj = (Object [])ll.get(0);
             if(obj[3]!=null)
		{
		Blob bo = (Blob)obj[3];
		InputStream insm = bo.getBinaryStream();
		byte [] fileContent = new byte [(int)bo.length()];
		insm.read(fileContent);
		String filetxt = new String (fileContent);
                request.setAttribute("filetxt", filetxt);
	        return  mapping.findForward("equityfile");
        }
    }