Shibboleth idP Custom Authentication RemoteUser

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HttpServletRequestWrapper.groovy
----

package com.acme

import java.util.HashMap;
import java.util.Map;

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

final class HttpServletRequestAddHeader extends HttpServletRequestWrapper {

 private Map<String, String> customHeaderMap = new HashMap();

 public HttpServletRequestAddHeader(final HttpServletRequest request) {
  super(request);
 }

 public final void addHeader(final String name, final String value){
  customHeaderMap[name] = value
 }

 @Override
 public final String getHeader(final String name) {
  final String paramValue = customHeaderMap[name]
  if (paramValue != null) {
      return paramValue
  }
  super.getHeader(name);
 }

 @Override
 public final String getRemoteUser() {
     getHeader('REMOTE_USER')
 }
}
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MyAuthenticationSuccessHandler.groovy
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package com.acme

import javax.servlet.ServletException
import javax.servlet.http.HttpServletRequest
import javax.servlet.http.HttpServletResponse
import javax.servlet.http.HttpSession
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken
import org.springframework.security.core.Authentication
import org.springframework.security.web.authentication.SimpleUrlAuthenticationSuccessHandler

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.security.core.context.SecurityContextHolder
import org.springframework.security.core.userdetails.User

final class MyAuthenticationSuccessHandler extends SimpleUrlAuthenticationSuccessHandler {
   private static final Logger logger = LoggerFactory.getLogger(ISEAuthenticationSuccessHandler.class);

    @Override
    protected String determineTargetUrl(HttpServletRequest request,
               HttpServletResponse response) {
        String context = request.getContextPath();
        String fullURL = request.getRequestURI();
        String url = fullURL.substring(fullURL.indexOf(context)+context.length());
        url;
    }

    @Override
    public void onAuthenticationSuccess(HttpServletRequest request,
               HttpServletResponse response, Authentication authentication)
      throws IOException, ServletException {

       User user = (User) authentication.principal
       String username = user.username;

       String url = determineTargetUrl(request,response);

       HttpServletRequestAddHeader newRequest = new HttpServletRequestAddHeader(request)

       newRequest.addHeader('REMOTE_USER', username);
       newRequest.getRequestDispatcher(url).forward(newRequest, response);
    }
}