binarywang/WxJava ? reverse-engineered prompt

Help me build a small Java backend that uses this WxJava SDK to connect to WeChat for a real app.

I want one clean starter project that shows how to set up the SDK and use the main parts I need, especially WeChat Pay and Official Account support, with a simple example for a mini program login too if it fits. Please make it easy to run locally, with clear config for app id, secret, merchant settings, and callback URLs, and add a few simple endpoints that demonstrate sending a payment request, handling a payment notification, and getting user info or login data from WeChat.

If there are better modules to use for each feature, pick the right ones and wire them together in a straightforward way. Keep it simple, practical, and ready to copy into a Spring Boot project. If you need current setup details, look up the latest docs online.