Merge pull request #1649 from jacobslei/master

fixed: handler 可能为非HandlerMethod 类型，出现类型转换异常

xxl-job-admin/src/main/java/com/xxl/job/admin/controller/resolver/WebExceptionResolver.java

@@ -34,10 +34,12 @@ public class WebExceptionResolver implements HandlerExceptionResolver {
 
 		// if json
 		boolean isJson = false;
-		HandlerMethod method = (HandlerMethod)handler;
+		if (handler instanceof HandlerMethod) {
-		ResponseBody responseBody = method.getMethodAnnotation(ResponseBody.class);
+			HandlerMethod method = (HandlerMethod)handler;
-		if (responseBody != null) {
+			ResponseBody responseBody = method.getMethodAnnotation(ResponseBody.class);
-			isJson = true;
+			if (responseBody != null) {
+				isJson = true;
+			}
 		}
 
 		// error result