1. 首先，在apollo-federation中定义一个Comment服务和一个Post服务：

// Comment服务 type Comment @key(fields: "id") { id: ID! postId: ID! text: String! }

extend type Query { getCommentById(id: ID!): Comment }

// Post服务 type Post @key(fields: "id") { id: ID! title: String! authorId: ID! }

extend type Query { getPostById(id: ID!): Post }

2. 然后，通过使用JS代码扩展Comment服务和Post服务来连接它们：

// 扩展Comment服务 const resolvers = { Comment: { post(comment) { return { __typename: 'Post', id: comment.postId }; }, }, }; const server = new ApolloServer({ schema: buildFederatedSchema([ { typeDefs: CommentServiceTypeDefs, resolvers, }, ]), });

// 扩展Post服务 const resolvers = { Post: { comments(post) { return [ { __typename: 'Comment', id: '1', text: 'Comment 1 for Post 1', postId: '1' }, { __typename: 'Comment', id: '2', text: 'Comment 2 for Post 1', postId: '1' }, { __typename: 'Comment', id: '3', text: 'Comment 1 for Post 2', postId: '2' }, { __typename: 'Comment', id: '4', text: 'Comment 2 for Post 2', postId: '2' }, ].filter(comment => comment.postId === post.id); }, }, }; const server = new ApolloServer({ schema: buildFederatedSchema([ { typeDefs: PostServiceTypeDefs, resolvers, }, ]), });

3. 最后，在Apollo Federation Gateway中设置服务：

// Apollo Federation Gateway中的服务设置 const gateway = new ApolloGateway({ serviceList: [ { name: 'comment-service', url: '[Comment Service URL]' }, { name: 'post-service', url: '[Post Service URL]' }, ], });

const server = new ApolloServer({ gateway, subscriptions: false, });

// 启动Apollo Federation Gateway服务器 server.listen().then(({ url }) => { console.log(� Gateway ready at ${url}); });