src/main/java/ai/giskard/learnspringwebsockets/LearnSpringWebsocketsApplication.java

package ai.giskard.learnspringwebsockets;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Collections;
import java.util.Enumeration;

@SpringBootApplication(exclude = {
        org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration.class,
        org.springframework.boot.actuate.autoconfigure.security.servlet.ManagementWebSecurityAutoConfiguration.class
})
public class LearnSpringWebsocketsApplication {

    public static void main(String[] args) {
        SpringApplication.run(LearnSpringWebsocketsApplication.class, args);
    }


    @Component
    static class RequestWrapperFilter extends OncePerRequestFilter {
        @Override
        protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
                throws ServletException, IOException {

            final HttpServletRequestWrapper reqWrapper = new HttpServletRequestWrapper(request) {
                @Override
                public Enumeration<String> getHeaders(String name) {
                    if ("connection".equals(name) && "UPGRADE".equals(super.getHeaders(name).nextElement())) {
                        return Collections.enumeration(Collections.singleton("Upgrade"));
                    }
                    return super.getHeaders(name);
                }

                @Override
                public String getHeader(String name) {
                    if ("connection".equals(name) && "UPGRADE".equals(super.getHeader(name))) {
                        return "Upgrade";
                    }
                    return super.getHeader(name);
                }
            };

            System.out.println("HEADERS: " + request.getServletPath());
            request.getHeaderNames().asIterator().forEachRemaining(s -> {
                System.out.println("HEADER: " + s + " = " + request.getHeader(s) + " ---> " + reqWrapper.getHeader(s));
            });

            filterChain.doFilter(reqWrapper, response);
        }
    }


}