title: Redirection inside reactive Spring Webflux REST controller
body: <p>I'm creating simple controller server for spring reactive project. While setting redirection to another location, I have found an error when calling <code>http://localhost:8080/</code>:</p>
  
  <pre><code>There was an unexpected error (type=Internal Server Error, status=500).
  ModelAttributeMethodArgumentResolver does not support multi-value reactive type wrapper: interface reactor.netty.http.server.HttpServerResponse
  java.lang.IllegalStateException: ModelAttributeMethodArgumentResolver does not support multi-value reactive type wrapper: interface reactor.netty.http.server.HttpServerResponse
      at org.springframework.util.Assert.state(Assert.java:94)
      at org.springframework.web.reactive.result.method.annotation.ModelAttributeMethodArgumentResolver.resolveArgument(ModelAttributeMethodArgumentResolver.java:112)
      at org.springframework.web.reactive.result.method.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:123)
      at org.springframework.web.reactive.result.method.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:190)
      at org.springframework.web.reactive.result.method.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:133)
      at org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter.lambda$handle$1(RequestMappingHandlerAdapter.java:200)
      at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:44)
  ...
  </code></pre>
  
  <p>This is the controller code:</p>
  
  <pre class="lang-java prettyprint-override"><code>import reactor.core.publisher.Mono;
  import reactor.netty.http.server.HttpServerResponse;
  
  @RestController
  public class BaseController {
      @GetMapping("/")
      public Mono&lt;Void&gt; indexController(HttpServerResponse response) {
  
          return response.sendRedirect("/api/v1");
      }
  // ...
  }
  </code></pre>
  
  <p>I expected it to be redirected from <code>localhost:8080/</code> to <code>localhost:8080/api/v1</code>. But I've got the above exception.</p>