use It in Spring Boot @RequestPart, Below is the example

@PostMapping public ResultModel sendNotification(@RequestPart("baseNotificationModel") EmailNotificationModel baseNotificationModel, @RequestPart(value = "file", required = false) MultipartFile[] file)

In postman do below changes to call API

Hello everyone, In postman choose Content-Type for both the Model(DTO) and file. If the column Content-Type isn't display then click on the Bulk edit and add column Content-Type.