Return type implementing DeferredResult is rejected with exception [SPR-14423]

[spring-projects-issues]

S. Paetzold opened SPR-14423 and commented

In Spring 4.1.1.RELEASE following code used to work:

@ResponseBody
@RequestMapping(value = "", method = PUT)
public CommandResult put(@Valid @RequestBody Record record) {
   ...
  CommandResult result = sendCommand(...);
  return result;
}

  private class CommandResult
    extends DeferredResult<Object>
    implements CommandCallback<Object> {

  @Override
  public void onSuccess(Object result) {
     setResult(result);
  }

  @Override
  public void onFailure(Throwable cause) {
    setErrorResult(cause);
  }
} 

Following exception is thrown:

java.lang.IllegalArgumentException: Expected one of Callable, DeferredResult, or ListenableFuture: class com.ysura.rest.controller.ActivityController$CommandResult
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod$ConcurrentResultMethodParameter.getParameterType(ServletInvocableHandlerMethod.java:273) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.ModelAndViewMethodReturnValueHandler.supportsReturnType(ModelAndViewMethodReturnValueHandler.java:72) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.selectHandler(HandlerMethodReturnValueHandlerComposite.java:90) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:77) ~[spring-web-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:832) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:743) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:961) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:895) ~[spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at org.springframework.web.servlet.FrameworkServlet.doPut(FrameworkServlet.java:880) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) [jetty-runner-9.3.6.v20151106.jar:9.3.6.v20151106]
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843) [spring-webmvc-4.2.6.RELEASE.jar:4.2.6.RELEASE]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jetty-runner-9.3.6.v20151106.jar:9.3.6.v20151106]
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:821) [jetty-runner-9.3.6.v20151106.jar:9.3.6.v20151106]
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1685) [jetty-runner-9.3.6.v20151106.jar:9.3.6.v20151106]
...

If the method return type is simply changed to DeferredResult<Object> it starts working again!

---

Affects: 4.2.6

Issue Links:

• HTTP Streaming and Server-Sent Events (SSE) [SPR-12212] #16826 HTTP Streaming and Server-Sent Events (SSE)

Referenced from: commits 4ddd957, cfc560c

Backported to: 4.2.7

[spring-projects-issues]

Juergen Hoeller commented

That assertion - a consequence of #16826 - seems too harsh: We're trying to find out about the generically specified body type, whereas a custom class may indeed substitute that in an extends or implements clause. We'll relax this for 4.2.7 and 4.3.1.

[spring-projects-issues]

Juergen Hoeller commented

I can only reproduce this when such a handler method returns null... Could you confirm whether this is the case in your scenario as well?

[spring-projects-issues]

S. Paetzold commented

Yes that is the case! In a non-error scenario null is returned. I'm basically only interested in exceptions.

[spring-projects-issues]

Juergen Hoeller commented

This is available in the latest 4.3.1.BUILD-SNAPSHOT as well as 4.2.7.BUILD-SNAPSHOT now. Please give it an early try if you have the chance...