Spring Boot Override ContentType Header

ContentTypeOverrideFilter.java

import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletRequestWrapper;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import java.io.IOException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Set;

@Component
class ContentTypeOverrideFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        String originalContentType = request.getHeader("Content-Type");
        System.out.println("originalContentType = " + originalContentType);
        HttpServletRequest requestToUse = new ContentTypeRequestWrapper(request);
        filterChain.doFilter(requestToUse, response);
    }

    private static class ContentTypeRequestWrapper extends HttpServletRequestWrapper {
        public ContentTypeRequestWrapper(HttpServletRequest request) {
            super(request);
        }

        @Override
        public String getContentType() {
            return "application/json";
        }

        @Override
        public String getHeader(String name) {
            if("content-type".equalsIgnoreCase(name)) {
                return getContentType();
            }
            return super.getHeader(name);
        }

        @Override
        public Enumeration<String> getHeaders(String name) {
            if("content-type".equalsIgnoreCase(name)) {
                return Collections.enumeration(Set.of(getContentType()));
            }
            return super.getHeaders(name);
        }
    }
}