Why @RequestHeader doesn't catch custom header added in filter

Question

Why I don't get the value in the method parameter@RequestHeader("Custom-Header"), although I get it in @RequestHeader Map<String,String> headers?

Initially, the request comes to the server without the "Custom-Header", I add it in my filter. After that, the request falls into the method, but the spring cannot insert the header in parameter @RequestHeader("Custom-Header"). Why?

method:

    @PostMapping("/support")
        public SupportView sendEmailToSupport(/*@Validated MessageView supportView,*/
                @RequestHeader Map<String, String> headers, //there is a header
                @RequestHeader(value = CUSTOM_HEADER, required = false) String customHeader) { //but not here
            SupportView supportView = helpDeskService.sendEmailToSupport(null, customHeader);
            return supportView;
        }

filter:

public class HeaderChangerFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        MutableHttpServletRequestWrapper request = new MutableHttpServletRequestWrapper((HttpServletRequest) servletRequest);

        String oldHeaderValue = request.getHeader(OLD_HEADER);
        String newHeaderValue = request.getHeader(CUSTOM_HEADER);

        if (oldHeaderValue != null && newHeaderValue == null) {
            request.putHeader(CUSTOM_HEADER, RequestHeaderUtils.getOldHeaderValue(request));
        }

        filterChain.doFilter(request, servletResponse); //CUSTOM_HEADER has in request headers
    }}

request delegation:

import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class MutableHttpServletRequestWrapper extends HttpServletRequestWrapper {
    // holds a custom header and value mapping
    private final Map<String, String> customHeaders;

    public MutableHttpServletRequestWrapper(HttpServletRequest request){
        super(request);
        this.customHeaders = new HashMap<>();
    }

    public void putHeader(String name, String value){
        this.customHeaders.put(name, value);
    }

    @Override
    public String getHeader(String name) {
        // check the custom headers first
        String headerValue = customHeaders.get(name);

        if (headerValue != null){
            return headerValue;
        }
        // else return from into the original wrapped object
        return ((HttpServletRequest) getRequest()).getHeader(name);
    }

    @Override
    public Enumeration<String> getHeaderNames() {
        // create a set of the custom header names
        Set<String> set = new HashSet<>(customHeaders.keySet());

        // now add the headers from the wrapped request object
        Enumeration<String> e = ((HttpServletRequest) getRequest()).getHeaderNames();
        while (e.hasMoreElements()) {
            // add the names of the request headers into the list
            String n = e.nextElement();
            set.add(n);
        }

        // create an enumeration from the set and return
        return Collections.enumeration(set);
    }
}

What does your MutableHttpServletRequestWrapper look like. How does it implement the getHeader method and all of its friends? — M. Deinum
– M. Deinum, Commented Apr 2, 2020 at 18:19
@M.Deinum pinned. This is just a delegate of HttpServletRequest readable object. Required for adding of my custom header. — Vladislav Solopov
– Vladislav Solopov, Commented Apr 2, 2020 at 19:41

hxy · Accepted Answer · 2020-09-05 02:37:32Z

2

You can override getHeaders() method.

@Override
public Enumeration<String> getHeaders(String name) {
    String values = getHeader(name);
    Set<String> set = Arrays.asList(values.split(",")).stream().collect(Collectors.toSet());
    if (customHeaders.containsKey(name)) {
       return Collections.enumeration(set);
    }
    return super.getHeaders(name);
}

edited Sep 5, 2020 at 2:37

answered Sep 4, 2020 at 9:55

hxy

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Vladislav Solopov Over a year ago

When should I override method?

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