[FIXED] Servlet Filter: How to get all the headers from servletRequest?

Issue

Here is how my WebFilter looks like

@WebFilter("/rest/*")
public class AuthTokenValidatorFilter implements Filter {

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

    @Override
    public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain) throws IOException, ServletException {
        final Enumeration<String> attributeNames = servletRequest.getAttributeNames();
        while (attributeNames.hasMoreElements()) {
            System.out.println("{attribute} " + servletRequest.getParameter(attributeNames.nextElement()));
        }

        final Enumeration<String> parameterNames = servletRequest.getParameterNames();
        while (parameterNames.hasMoreElements()) {
            System.out.println("{parameter} " + servletRequest.getParameter(parameterNames.nextElement()));
        }
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {
    }
}

I tried to find out online as to how to get values for HTTP headers coming from request.

I did not find anything, so I tried to enumerate on servletRequest.getAttributeNames() and servletRequest.getParameterNames() without knowing anything, but I do not get any headers.

Question
How can I get all the headers coming from the request?

Solution

Typecast ServletRequest into HttpServletRequest (only if ServletRequest request is an instanceof HttpServletRequest).

Then you can use HttpServletRequest.getHeader() and HttpServletRequest.getHeaderNames() method.

Something like this:

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    HttpServletRequest httpRequest = (HttpServletRequest) request;
    Enumeration<String> headerNames = httpRequest.getHeaderNames();

    if (headerNames != null) {
            while (headerNames.hasMoreElements()) {
                    System.out.println("Header: " + httpRequest.getHeader(headerNames.nextElement()));
            }
    }

    //doFilter
    chain.doFilter(httpRequest, response);
}

Answered By - Buhake Sindi