Servlet Filter: How to Get All the Headers from servletRequest?
Here Is How My Webfilter Looks Like @Webfilter("/Rest/*") Public Class Authtokenvalidatorfilter Implements Filter { @Override Public Void Init(Final...
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;
}));
David Miller brings 15 years of experience in global economics, personal finance strategy, and market dynamics. He specializes in turning complex economic trends into actionable insights for everyday readers.
