Cached POST body for HttpServletRequest. Inspired from http://natch3z.blogspot.com/2009/01/read-request-body-in-filter.html

CachedBodyHttpServletRequest.java

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public final class CachedBodyHttpServletRequest extends HttpServletRequestWrapper {
    private String body;
    private final HttpServletRequest request;

    public CachedBodyHttpServletRequest(HttpServletRequest request) {
        super(request);

        this.request = request;
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(getBody().getBytes());

        return new ServletInputStream() {
            @Override
            public int read() {
                return byteArrayInputStream.read();
            }

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

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

            @Override
            public void setReadListener(ReadListener readListener) {
                // Nothing to set here.
            }
        };
    }

    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }

    private String getBody() throws IOException {
        if (body == null) {
            try (Scanner scanner = new Scanner(request.getInputStream(), request.getCharacterEncoding())) {
                final String maybeBody = scanner.next("\\A");

                body = maybeBody != null ? maybeBody : "";
            }
        }

        return body;
    }
}