I keep encountering "signature errors" when using the "Unified Ordering" interface of WeChat Pay. Generally, it may be the following problems.

1. The ASCII codes of the parameter names are not arranged in ascending order, or the generated MD5 string is not converted to uppercase by toUpperCase. The solution to this problem is very simple. Just go to the WeChat official website and use the verification tool to verify it.

2.key error. Pay special attention here, the key of the public platform and the key of the merchant account are different! ! ! After the WeChat payment is successfully reviewed, you will receive an email with the appid merchant number, merchant backend login number and password. Log in to the merchant backend: Account Settings - Security Settings - Switch to API Security, download the certificate, there is an api below Key, enter a string and save it. The subsequent two signatures will use this manually set key! ! !

Finally, I would like to remind everyone that you must read emails and documents carefully in the future.