GraphQL 例程：图书管理 API

目标

实现一个完整的图书管理 GraphQL 服务，涵盖：Schema 定义、Query（查询）、Mutation（变更）、嵌套类型（Author ↔ Book）。

完整代码

const { ApolloServer } = require('@apollo/server');
const { startStandaloneServer } = require('@apollo/server/standalone');

// ── 数据 ──
const authors = [
  { id: '1', name: '余华' },
  { id: '2', name: '村上春树' },
];

const books = [
  { id: '1', title: '活着', authorId: '1', year: 1992 },
  { id: '2', title: '许三观卖血记', authorId: '1', year: 1995 },
  { id: '3', title: '挪威的森林', authorId: '2', year: 1987 },
];

// ── Schema ──
const typeDefs = `#graphql
  type Author {
    id: ID!
    name: String!
    books: [Book!]!
  }

  type Book {
    id: ID!
    title: String!
    year: Int!
    author: Author!
  }

  type Query {
    books: [Book!]!
    book(id: ID!): Book
    authors: [Author!]!
    author(id: ID!): Author
  }

  type Mutation {
    addBook(title: String!, authorId: ID!, year: Int!): Book!
    deleteBook(id: ID!): Boolean!
  }
`;

// ── Resolver ──
const resolvers = {
  Query: {
    books: () => books,
    book: (_, { id }) => books.find(b => b.id === id),
    authors: () => authors,
    author: (_, { id }) => authors.find(a => a.id === id),
  },
  Book: {
    author: (book) => authors.find(a => a.id === book.authorId),
  },
  Author: {
    books: (author) => books.filter(b => b.authorId === author.id),
  },
  Mutation: {
    addBook: (_, { title, authorId, year }) => {
      const id = String(books.length + 1);
      const newBook = { id, title, authorId, year };
      books.push(newBook);
      return newBook;
    },
    deleteBook: (_, { id }) => {
      const idx = books.findIndex(b => b.id === id);
      if (idx === -1) return false;
      books.splice(idx, 1);
      return true;
    },
  },
};

// ── 启动 ──
const server = new ApolloServer({ typeDefs, resolvers });

startStandaloneServer(server, { listen: { port: 4000 } }).then(({ url }) => {
  console.log(`🚀 服务运行在: ${url}`);
});

测试查询

访问 http://localhost:4000 Apollo Sandbox，执行：

# 查询所有图书 + 嵌套作者信息
query {
  books {
    title
    year
    author {
      name
      books {
        title
      }
    }
  }
}

# 添加图书
mutation {
  addBook(title: "兄弟", authorId: "1", year: 2005) {
    id
    title
    author { name }
  }
}

预期输出

{
  "data": {
    "books": [
      {
        "title": "活着",
        "year": 1992,
        "author": { "name": "余华", "books": [ ... ] }
      },
      ...
    ]
  }
}

关键点

概念	说明
!	表示 Non-Null，该字段不能为 null
[Book!]!	列表不能为 null，列表内的元素也不能为 null
嵌套 Resolver	Book.author 独立解析，可单独优化
Mutation 返回	返回变更后的实体（最佳实践）