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?
3 Answers
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); } With Java 8+ you can use a stream to collect request headers:
HttpServletRequest httpRequest = (HttpServletRequest) request; Map<String, String> headers = Collections.list(httpRequest.getHeaderNames()) .stream() .collect(Collectors.toMap(h -> h, httpRequest::getHeader)); UPDATED
@Matthias reminded me that headers can have multiple values:
Map<String, List<String>>
Map<String, List<String>> headersMap = Collections.list(httpRequest.getHeaderNames()) .stream() .collect(Collectors.toMap( Function.identity(), h -> Collections.list(httpRequest.getHeaders(h)) )); org.springframework.http.HttpHeaders
HttpHeaders httpHeaders = Collections.list(httpRequest.getHeaderNames()) .stream() .collect(Collectors.toMap( Function.identity(), h -> Collections.list(httpRequest.getHeaders(h)), (oldValue, newValue) -> newValue, HttpHeaders::new )); You should consider that the same HTTP header can occur multiple times with different values:
Map<String, Serializable> headers = Collections.list(request.getHeaderNames()).stream().collect(Collectors.toMap(h -> h, h -> { ArrayList<String> headerValues = Collections.list(request.getHeaders(h)); return headerValues.size() == 1 ? headerValues.get(0) : headerValues; })); 
