@MessgeMapping support for Optional<Principal>

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/PrincipalMethodArgumentResolver.java

@@ -17,6 +17,7 @@
 package org.springframework.messaging.simp.annotation.support;
 
 import java.security.Principal;
+import java.util.Optional;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.messaging.Message;
@@ -24,7 +25,7 @@ import org.springframework.messaging.handler.invocation.HandlerMethodArgumentRes
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
 
 /**
- * {@link HandlerMethodArgumentResolver} to a {@link Principal}.
+ * {@link HandlerMethodArgumentResolver} to a {@link Principal} or {@link Optional} of {@link Principal}.
  *
  * @author Rossen Stoyanchev
  * @since 4.0
@@ -33,17 +34,19 @@ public class PrincipalMethodArgumentResolver implements HandlerMethodArgumentRes
 
 	@Override
 	public boolean supportsParameter(MethodParameter parameter) {
-		Class<?> paramType = parameter.getParameterType();
+		MethodParameter nestedParameter = parameter.nestedIfOptional();
+		Class<?> paramType = nestedParameter.getNestedParameterType();
 		return Principal.class.isAssignableFrom(paramType);
 	}
 
 	@Override
-	public Object resolveArgument(MethodParameter parameter, Message<?> message) throws Exception {
+	public Object resolveArgument(MethodParameter parameter, Message<?> message){
 		Principal user = SimpMessageHeaderAccessor.getUser(message.getHeaders());
-		if (user == null) {
-			throw new MissingSessionUserException(message);
+		if (parameter.isOptional()) {
+			return Optional.ofNullable(user);
+		} else {
+			return user;
 		}
-		return user;
 	}
 
 }