Java implementation of wechat applet login status maintenance example code

I believe many friends who like development already know what kind of wechat applet is. The landlord has been paying attention to it since the internal test of the applet, and has also written several wechat applets that have been online. But they are basically written in the pure front end. Recently, the landlord wrote a complete small program project from the back end to the front end. He encountered some problems in the middle. The landlord will find some points of personal learning value to share with you from time to time. I hope it will be of some help to you.

Let's start with the most basic login status maintenance of wechat applet. The official API document of the applet has a complete explanation of the login status and relevant code. If you want to see the details, you can go out and turn right: https://mp.weixin.qq.com/debug/wxadoc/dev/api/api-login.html#wxloginobject I didn't understand much when I first read it, and the code didn't provide a java version, which embarrassed a java programmer, so after studying hard, I decided to make a simple demo of the Java version.

https://api.weixin.qq.com/sns/jscode2session?appid=APPID&secret=SECRET&js_code=JSCODE&grant_type=authorization_code