http filter里面请求读取之后再次读取读取不到

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HttpServletRequest request = (HttpServletRequest) req; ServletInputStream is = req.getInputStream(); int length=req.getContentLength(); byte [] ba = new byte [length];

以上代码在doFilter中读取了post请求的内容,之后发现servlet已经无法读取该内容,因为ServletInputStream不支持mark,没法回头