1. 在Apollo Server中设置Gateway的SelectionSetTransformer配置项：

const server = new ApolloServer({
  gateway,
  subscriptions: false,
  context: ({ req }) => ({ req }),
  plugins: [
    {
      requestDidStart() {
        return {
          async didResolveOperation({ operation }) {
            operation.selectionSet = await gateway.transformRequest({
              document: operation.query,
              variables: operation.variables,
              operationName: operation.operationName,
              context: {}
            }).document.definitions[0].selectionSet;
          }
        };
      }
    }
  ]
});

server.listen().then(({ url }) => {
  console.log(`Server ready at ${url}`);
});

2. 模拟GraphQL查询：

const { request } = require('graphql-request');
const { ApolloGateway } = require('@apollo/gateway');

const gateway = new ApolloGateway({
  serviceList: [
    { name: 'accounts', url: 'http://localhost:4001' },
    { name: 'inventory', url: 'http://localhost:4002' },
    { name: 'products', url: 'http://localhost:4003' },
  ],
});

const query = `
  query Products {
    products {
      id
      name
      image
    } 
  }
`;

async function makeGatewayRequest() {
  const { data } = await gateway.load({
    query,
    context: {},
  });

  console.log('Data received:', data);

  const { request: subRequest } = data.products;

  const subResponse = await request(subRequest.url, subRequest.query, subRequest.variables);

  console.log('Sub response received:', subResponse);
}

makeGatewayRequest();