XPay
XPay's personal visa-free payment system is completely free
...Its unsigned personal-payment workflow relies on user review and email-based confirmation instead of continuously monitoring payment apps. Mobile payment scenarios can be integrated with H5 pages, applications, and mini programs. The backend uses Spring Boot, Spring MVC, Spring Data JPA, MySQL, Redis, Thymeleaf, and Swagger. Scheduled tasks, asynchronous operations, email notifications, and configurable QR-code pages support the surrounding payment workflow.