public class MyRequestWrapper extends HttpServletRequestWrapper {
 private final String body;
 public MyRequestWrapper(HttpServletRequest request) throws IOException {
  super(request);
  this.body = RequestReadUtils.read(request);
 }
 public String getBody() {
  return body;
 }
 @Override
 public ServletInputStream getInputStream() throws IOException {
  final ByteArrayInputStream bais = new ByteArrayInputStream(body.getBytes());  
  return new ServletInputStream() {
   ...略
  };
 }
 @Override
 public BufferedReader getReader() throws IOException {
  return new BufferedReader(new InputStreamReader(this.getInputStream()));
 }
}

private static final int BUFFER_SIZE = 1024 * 8;
  
    public static String read(HttpServletRequest request) throws IOException {
        BufferedReader bufferedReader = request.getReader();
        for (Enumeration<String> iterator = request.getHeaderNames(); iterator.hasMoreElements();) {
         String type = iterator.nextElement();
   System.out.println(type+" = "+request.getHeader(type));
  }
        System.out.println();
        StringWriter writer = new StringWriter();
        write(bufferedReader,writer);
        return writer.getBuffer().toString();
    }
 
    public static long write(Reader reader,Writer writer) throws IOException {
        return write(reader, writer, BUFFER_SIZE);
    }
 
    public static long write(Reader reader, Writer writer, int bufferSize) throws IOException
    {
        int read;
        long total = 0;
        char[] buf = new char[bufferSize];
        while( ( read = reader.read(buf) ) != -1 ) {
            writer.write(buf, 0, read);
            total += read;
        }
        return total;
    }

@WebFilter
public class TestFilter implements Filter{
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain){
  HttpServletRequest request = (HttpServletRequest) servletRequest;
  HttpServletResponse response = (HttpServletResponse) servletResponse;
  
  MyRequestWrapper wrapper = WebUtils.getNativeRequest(request, MyRequestWrapper.class);
  chain.doFilter(wrapper == null ? new MyRequestWrapper(request) :wrapper,servletRequest);
 }
}

BufferedReader bufferedReader = request.getReader();
-----------------
char[] buf = new char[bufferSize];
while( ( read = reader.read(buf) ) != -1 ) {
    writer.write(buf, 0, read);
    total += read;
}

public class MyRequestWrapper extends HttpServletRequestWrapper {
 private final String body;
 public MyRequestWrapper(HttpServletRequest request) throws IOException {
  super(request);
  this.body = getBodyString(request);
 }
 public String getBody() {
  return body;
 }
 
 public String getBodyString(final HttpServletRequest request) throws IOException {
     String contentType = request.getContentType();
     String bodyString = "";
     StringBuilder sb = new StringBuilder();
     if (StringUtils.isNotBlank(contentType) && (contentType.contains("multipart/form-data") || contentType.contains("x-www-form-urlencoded"))) {
         Map<String, String[]> parameterMap = request.getParameterMap();
         for (Map.Entry<String, String[]> next : parameterMap.entrySet()) {
             String[] values = next.getValue();
             String value = null;
             if (values != null) {
                 if (values.length == 1) {
                     value = values[0];
                 } else {
                     value = Arrays.toString(values);
                 }
             }
             sb.append(next.getKey()).append("=").append(value).append("&");
         }
         if (sb.length() > 0) {
             bodyString = sb.toString().substring(0, sb.toString().length() - 1);
         }
         return bodyString;
     } else {
         return IOUtils.toString(request.getInputStream());
     }
 }
 @Override
 public ServletInputStream getInputStream() throws IOException {
  final ByteArrayInputStream bais = new ByteArrayInputStream(body.getBytes());
  
  return new ServletInputStream() {
   @Override
   public boolean isFinished() {
    return false;
   }
   @Override
   public boolean isReady() {
    return false;
   }
   @Override
   public int read() {
    return bais.read();
   }
   @Override
   public void setReadListener(ReadListener readListener) {
   }
  };
 }
 @Override
 public BufferedReader getReader() throws IOException {
  return new BufferedReader(new InputStreamReader(this.getInputStream()));
 }
}