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在使用Servlet进行Web开发的时候，有时候为了增加必要的业务处理而又不想修改现有的程序，往往采用Filter。这样在各个Filter中可能都要读取ServletInputStream流的内容，而ServletInputStream却只能读一次，这时候必须备份HttpServleRequest。

class BufferedServletInputStream extends ServletInputStream {    private ByteArrayInputStream inputStream;    public BufferedServletInputStream(byte[] buffer) {        this.inputStream = new ByteArrayInputStream( buffer );    }    @Override    public int available() throws IOException {        return inputStream.available();    }    @Override    public int read() throws IOException {        return inputStream.read();    }    @Override    public int read(byte[] b, int off, int len) throws IOException {        return inputStream.read( b, off, len );    }}class BufferedServletRequestWrapper extends HttpServletRequestWrapper {    private byte[] buffer;    public BufferedServletRequestWrapper(HttpServletRequest request) throws IOException {        super( request );        InputStream is = request.getInputStream();        ByteArrayOutputStream baos = new ByteArrayOutputStream();        byte buff[] = new byte[ 1024 ];        int read;        while( ( read = is.read( buff ) ) > 0 ) {            baos.write( buff, 0, read );        }        this.buffer = baos.toByteArray();    }    @Override    public ServletInputStream getInputStream() throws IOException {        return new BufferedServletInputStream( this.buffer );    }}

在Filter的doFilter（）或者Servlet的doPost（）中，

//备份HttpServletRequestHttpServletRequest httpRequest = (HttpServletRequest)request;httpRequest = new BufferedServletRequestWrapper( httpRequest );//使用流InputStream is = request.getInputStream();//其他业务逻辑//将request 传到下一个Filterchain.doFilter(request, response);