There are a lot of codegen tools to do it, like:
And the whole schema of Shopify GraphQL could be fetched via a GraphQL request if you are familiar with GraphQL. It's sort of a self-described thing in GraphQL.
Here's a SDK on Github: https://github.com/YuanWenqing/shopify4j , which contains both GraphQL schemas of Admin GraphQL and Storefront GraphQL.
GraphQL queries to request the schema can also be found there. You may find the similar query by hacking the request when loading a Shopify GraphQL Explorer.