Servlet Filter modify header value with servlet request wrapper not working

Question

I am attempting to change the Content-Type header in a request and change it to "application/json" before it reaches my spring rest controller. I have created a servlet request wrapper to change the values, but when the request reaches the controller it is still "text/plain". The logging shows that the header value has been changed before hitting doFilter();

Here is my class extending HttpServletRequestWrapper

class HttpServletRequestWritableWrapper extends HttpServletRequestWrapper {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(HttpServletRequestWritableWrapper.class);
private final ByteArrayInputStream decryptedBody;

HttpServletRequestWritableWrapper(HttpServletRequest request, byte[] decryptedData) {
    super(request);
    decryptedBody = new ByteArrayInputStream(decryptedData);
}



@Override
public String getHeader(String name) {
    String headerValue = super.getHeader(name);
    if("Accept".equalsIgnoreCase(name))
    {
        logger.debug("Accept header changing :");
        return headerValue.replaceAll(
                MediaType.TEXT_PLAIN_VALUE, MediaType.APPLICATION_JSON_VALUE
        );
    }
    else if ("Content-Type".equalsIgnoreCase(name))
    {
        logger.debug("Content type change: ");
        return headerValue.replaceAll(MediaType.TEXT_PLAIN_VALUE, MediaType.APPLICATION_JSON_VALUE);
    }
    return headerValue;
}

@Override
public Enumeration<String> getHeaderNames() {
    return super.getHeaderNames();
}

@Override
public String getContentType() {
    String contentTypeValue = super.getContentType();
    if (MediaType.TEXT_PLAIN_VALUE.equalsIgnoreCase(contentTypeValue)) {
        logger.debug("Changing on getContentType():");
        return MediaType.APPLICATION_JSON_VALUE;
    }
    return contentTypeValue;
}


@Override
public BufferedReader getReader() throws UnsupportedEncodingException {
    return new BufferedReader(new InputStreamReader(decryptedBody, UTF_8));
}

@Override
public ServletInputStream getInputStream() throws IOException {
    return new ServletInputStream() {
        @Override
        public int read() {
            return decryptedBody.read();
        }
    };
}

And here is my filter:

@WebFilter(displayName = "EncryptionFilter", urlPatterns = "/*")
public class EncryptionFilter implements Filter {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(EncryptionFilter.class);

@Override
public void init(FilterConfig filterConfig) throws ServletException {

}

@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    byte[] data = "{\"currentClientVersion\":{\"majorElement\":\"1\",\"minorElement\":\"2\"}}".getBytes();

    logger.debug("data string " + data.toString());

    logger.debug("Content-type before: " + servletRequest.getContentType());

    HttpServletRequest request = (HttpServletRequest) servletRequest;
    HttpServletRequestWritableWrapper requestWrapper = new HttpServletRequestWritableWrapper(request, data);
    //logger.debug("Accept Header: " + requestWrapper.getHeader("Accept"));
    //logger.debug("Content-Type: " + requestWrapper.getHeader("Content-Type"));
    //logger.debug("Contenttype" + requestWrapper.getContentType());

    filterChain.doFilter(requestWrapper, servletResponse);


}

@Override
public void destroy() {

}


}

Answer 1

It appears that the getHeaders method was being called somewhere else after my filter and not returning the headers with my updated values.

I added this override in my HttpServletRequestWrapper and it is now working:

@Override
public Enumeration<String> getHeaders(String name) {
    List<String> headerVals = Collections.list(super.getHeaders(name));
    int index = 0;
    for (String value : headerVals) {
        if ("Content-Type".equalsIgnoreCase(name)) {
            logger.debug("Content type change: ");
            headerVals.set(index, MediaType.APPLICATION_JSON_VALUE);
        }

        index++;
    }

    return Collections.enumeration(headerVals);
}