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

Question

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?

Answer 1

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); }