Fix type check for ResponseEntity<ResponseBodyEmitter>

Issue: SPR-12693

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterReturnValueHandler.java

@@ -26,6 +26,7 @@ import javax.servlet.http.HttpServletResponse;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
@@ -66,14 +67,8 @@ public class ResponseBodyEmitterReturnValueHandler implements HandlerMethodRetur
 			return true;
 		}
 		else if (ResponseEntity.class.isAssignableFrom(returnType.getParameterType())) {
-			Type paramType = returnType.getGenericParameterType();
-			if (paramType instanceof ParameterizedType) {
-				ParameterizedType type = (ParameterizedType) paramType;
-				Type[] typeArguments = type.getActualTypeArguments();
-				if (typeArguments.length == 1) {
-					return ResponseBodyEmitter.class.isAssignableFrom((Class<?>) typeArguments[0]);
-				}
-			}
+			Class<?> bodyType = ResolvableType.forMethodParameter(returnType).getGeneric(0).resolve();
+			return (bodyType != null && ResponseBodyEmitter.class.isAssignableFrom(bodyType));
 		}
 		return false;
 	}

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterReturnValueHandlerTests.java

@@ -18,6 +18,7 @@ package org.springframework.web.servlet.mvc.method.annotation;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -86,6 +87,7 @@ public class ResponseBodyEmitterReturnValueHandlerTests {
 		assertTrue(this.handler.supportsReturnType(returnType(TestController.class, "handleSse")));
 		assertTrue(this.handler.supportsReturnType(returnType(TestController.class, "handleResponseEntity")));
 		assertFalse(this.handler.supportsReturnType(returnType(TestController.class, "handleResponseEntityString")));
+		assertFalse(this.handler.supportsReturnType(returnType(TestController.class, "handleResponseEntityParameterized")));
 	}
 
 	@Test
@@ -207,6 +209,10 @@ public class ResponseBodyEmitterReturnValueHandlerTests {
 			return null;
 		}
 
+		private ResponseEntity<AtomicReference<String>> handleResponseEntityParameterized() {
+			return null;
+		}
+
 	}
 
 	private static class SimpleBean {