Component-level data fetching in JSS Next.js apps

Abstract

Overview of how JSS Next.js apps retrieve component-level data and how it can be accessed

Next.js provides the ability to prerender pages at build time or on each request using page-level data fetching strategies for each rendering form.

If you want to fetch component-specific data at the component level, you can use a mechanism similar to page-level data fetching by implementing and exporting getStaticProps for static generation (SG) or getServerSideProps for server-side rendering (SSR).

Watch the following video for a demonstration of how component-level data fetching works in a JSS app:

The ComponentPropsService

The SitecorePagePropsFactory class uses an instance of the ComponentPropsService class that helps to identify which components require retrieval of data. The ComponentPropsService class is provided by the NPM package @sitecore-jss/sitecore-jss-nextjs.

The ComponentPropsService class accepts the following parameters:

componentModule - a function returning a Next.js component using the componentName argument. You can find the componentModule function definition in the src/temp/componentFactory file. If not present, generate it by running scripts/bootstrap.ts.
layoutData - Layout Service data for your page.
context - the Next.js SSG or SSR context.

The ComponentPropsService class traverses the layout service data and looks at all the renderings. To find the components that require data fetching, the service watches the component using the rendering.componentName property against the list of component registrations in the src/temp/componentFactory file.

If the component defines and exports the functions getStaticProps or getServerSideProps, the ComponentPropsService class runs the function. After applying all side effects, it stores the component data in a componentProps object in the format { [rendering.uid]: data }.

For example, the following component defines a data-fetching function and displays the injected component props.

Note

This example component contains an implementation of both getStaticProps and getServerSideProps functions. In a real component, you must define only one of them, depending on the rendering mode you chose.

import {
  Text,
  RichText,
  Field,
  GetServerSideComponentProps,
  GetStaticComponentProps,
  withDatasourceCheck
} from '@sitecore-jss/sitecore-jss-nextjs';
import { ComponentParams, ComponentRendering,} from '@sitecore-jss/sitecore-jss-nextjs';

type ComponentProps = {
  rendering: ComponentRendering;
  params: ComponentParams;
};

type ContentBlockProps = ComponentProps & {
  fields: {
    heading: Field<string>;
    content: Field<string>;
  };
};

const ContentBlock = ({ fields }: ContentBlockProps): JSX.Element => (
  <div className="contentBlock">
    <Text tag="h2" className="contentTitle" field={fields.heading} />
    <RichText className="contentDescription" field={fields.content} />
  </div>
);

const fetchPost = () =>
  fetch('https://jsonplaceholder.typicode.com/posts/1').then((res) => res.json());

export const getStaticProps: GetStaticComponentProps = async (rendering, layoutData, context) => {
  const post = await fetchPost();
  return post;
};

export const getServerSideProps: GetServerSideComponentProps = async (rendering, layoutData) => {
  const post = await fetchPost();
  return post;
};

export default withDatasourceCheck()<ContentBlockProps>(ContentBlock);