title: Spring boot (with security) behind Kong reverse proxy not working correctly
body: <p>I have a spring boot service with security over Keycloak.
  The Service is working fine: <a href="http://localhost:8080/api/resource" rel="nofollow noreferrer">http://localhost:8080/api/resource</a> (is restricted) and only after authentication via keycloak accessible.</p>
  
  <pre><code>@Override
  protected void configure(HttpSecurity http) throws Exception {
      super.configure(http);
      http.authorizeRequests().antMatchers("/open/*").permitAll()
      .anyRequest().authenticated();
  }
  </code></pre>
  
  <p>Now i am using Kong as reverse proxy for the wolrd outside: The entry for that is (for instance): <a href="https://gateway.example.com/customer" rel="nofollow noreferrer">https://gateway.example.com/customer</a> which redirects to <a href="http://localhost:8080" rel="nofollow noreferrer">http://localhost:8080</a></p>
  
  <p>After calling <a href="https://gateway.example.com/customer/api/resource" rel="nofollow noreferrer">https://gateway.example.com/customer/api/resource</a>, something goes wrong, instead to call  <a href="https://gateway.example.com/customer/sso/login" rel="nofollow noreferrer">https://gateway.example.com/customer/sso/login</a> it calls <a href="https://gateway.example.com/sso/login" rel="nofollow noreferrer">https://gateway.example.com/sso/login</a> and so i get "404 Not Found".</p>
  
  <p>It seems that the security part remove or let's say ignore "customer" in the location.</p>
  
  <p>There is a possibility to correct the location?</p>
  
  <p>Thanks</p>