How to read json payload from gitlab webhook in Jenkins

[AIKiller]

I have a job using jenkins pipeline to deploy my project. now, I plan to use gitlab-hook-plugin to monitor the submission of projects on gitlab service. Once a user submits a project change, Jenkins reads the submit parameters and performs other operations according to the type of submission, for example: build and test. But then there is a problem, how do I read the parameters of the project change, such as submit log, branch, user name and other information.