Writing fetchers for GraphQL queries

You are going to write data fetchers in this section. Data fetchers, as the name suggests, retrieve the information from the source that is from a persistent store such as a database or a third-party API/document store. You will learn how to write data fetchers to retrieve a single field of data, a single object, and a collection of objects.

Writing the data fetcher for product

The data fetcher is a critical DSG component for serving GraphQL requests that fetches the data and the DSG internally resolves each of the fields. You mark them with the special @DgsComponent DGS annotation. These are types of Spring components that the DGS framework scans and uses for serving requests.

Let’s create a new file called ProductDatafetcher.java in the datafetchers package to represent a DGS data fetcher component. It will have a data fetcher method for serving the product query. You can add the following code to it:

@DgsComponentpublic class...