Merge pull request #23612 from KateVasovski/add-principal-method-argument-resolver

Author: rstoyanchev

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,14 +17,15 @@
 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;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
 
 /**
- * {@link HandlerMethodArgumentResolver} to a {@link Principal}.
+ * Resolver for arguments of type {@link Principal}, including {@code Optional<Principal>}.
  *
  * @author Rossen Stoyanchev
  * @since 4.0
@@ -33,17 +34,15 @@ 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);
-		}
-		return user;
+		return parameter.isOptional() ? Optional.ofNullable(user) : user;
 	}
 
 }