Post request body content cannot be retrieved repeatedly

post The request body content cannot be obtained repeatedly

Link to the original text https://zhhll.icu/2020/javaweb/ problem /6.post The request body content cannot be obtained repeatedly /

Why can't I read repeatedly ？

With tomcat For example , When reading the request body, the actual underlying call is org.apache.catalina.connector.Request Of getInputStream() Method , And the method returns CoyoteInputStream Input stream

public ServletInputStream getInputStream() throws IOException {
    

    if (usingReader) {
    
        throw new IllegalStateException(sm.getString("coyoteRequest.getInputStream.ise"));
    }

    usingInputStream = true;
    if (inputStream == null) {
    
        inputStream = new CoyoteInputStream(inputBuffer);
    }
    return inputStream;

}

In the use of CoyoteInputStream When reading

public int read(byte[] b, int off, int len) throws IOException {
    
  //  If the flow is closed , Throw an exception 
    if (closed) {
    
        throw new IOException(sm.getString("inputBuffer.streamClosed"));
    }
//  If you've finished reading , Then return to -1
    if (checkByteBufferEof()) {
    
        return -1;
    }
    int n = Math.min(len, bb.remaining());
    bb.get(b, off, n);
    return n;
}

When the stream is read, it will proceed close, This flow close after ,close The state is set to true, Therefore, the stream cannot be read twice

So what's the solution ？ take tomcat Of Request Class for re implementation ？ It's too expensive ,sun The company has provided solutions when designing , For requests and responses ,sun The company provides packaging , Sure HttpServletRequestWrapper Class packaging original request object , Realized HttpServletRequest All methods of the interface , The wrapped request Object's corresponding method ; Correspondingly, there are HttpServletResponseWrapper Class to wrap the original response Object inheritance HttpServletRequestWrapper To rewrite methods , have access to HttpServletResponseWrapper and HttpServletRequestWrapper To customize responses and requests

public class BodyReaderHttpServletRequestWrapper extends HttpServletRequestWrapper {
    
		//  Store request body 
    private byte[] body;

    private HttpServletRequest orgRequest;

    public BodyReaderHttpServletRequestWrapper(HttpServletRequest request) throws IOException {
    
        super(request);
        this.orgRequest = request;
        body = HttpHelper.getBody(request);
    }

    public HttpServletRequest getOrgRequest() {
    
        return this.orgRequest;
    }

  //  Rewrite read , Read from the stored byte array 
    @Override
    public BufferedReader getReader() throws IOException {
    
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }

  //  Rewrite read , Read from the stored byte array 
    @Override
    public ServletInputStream getInputStream() throws IOException {
    

        final ByteArrayInputStream bais = new ByteArrayInputStream(body);

        return new ServletInputStream() {
    

            @Override
            public int read() throws IOException {
    
                return bais.read();
            }

            @Override
            public boolean isFinished() {
    
                return false;
            }

            @Override
            public boolean isReady() {
    
                return false;
            }

            @Override
            public void setReadListener(ReadListener readListener) {
    

            }
        };
    }
}