如何基于给定输出与类型定义为Apollo GraphQL Server创建Resolver

以下是根据提供的示例输出数据和GraphQL类型定义，编写的Apollo GraphQL Server Resolver实现方案，包含完整代码和说明：

1. GraphQL类型定义（SDL） #

直接复用给定的类型定义：

type Bookdepartment {
  id: ID
  booksubdepartment: [Booksubdepartment]
}

type Booksubdepartment {
  id: ID
  departmentID: String
  books: [Book]
}

type Book {
  id: ID
  subdepartmentId: String
  bookTitle: String
}

type Query {
  bookdepartments: [Bookdepartment]
}

2. 模拟数据源 #

对应示例输出数据，定义用于测试的模拟数据源：

const mockData = {
  department: [
    {
      "id": "123",
      "booksubdepartment": [
        {
          "id": "111",
          "departmentID": "123",
          "books": [
            {
              "subdepartmentId":"111",
              "bookTitle": "Book One on sub department 111"
            },
            {
              "subdepartmentId":"111",
              "bookTitle": "Book Two on sub department 111"
            }
          ]
        },
        {
          "id": "222",
          "books": [
            {
              "subdepartmentId":"222",
              "bookTitle": "Book one on sub department 222"
            },
            {
              "subdepartmentId":"222",
              "bookTitle": "Book two on sub department 222"
            }
          ]
        }
      ]
    },
    {
      "id": "345",
      "booksubdepartment": [
        {
          "id": "333",
          "departmentID": "345",
          "books": [
            {
              "subdepartmentId":"333",
              "bookTitle": "Book one on sub department 333"
            },
            {
              "subdepartmentId":"333",
              "bookTitle": "Book two on sub department 333"
            }
          ]
        },
        {
          "id": "444",
          "books": [
            {
              "subdepartmentId":"444",
              "bookTitle": "Book one on sub department 444"
            },
            {
              "subdepartmentId":"444",
              "bookTitle": "Book two on sub department 444"
            }
          ]
        }
      ]
    }
  ]
};

3. Resolver实现 #

Resolver需要处理三个核心点：提供查询入口、补全子部门缺失的departmentID字段、为Book生成符合类型定义的id字段，完整代码如下：

const resolvers = {
  Query: {
    // 查询入口：返回所有部门数据
    bookdepartments: () => mockData.department,
  },
  Bookdepartment: {
    // 解析子部门字段，补全缺失的departmentID
    booksubdepartment: (parent) => {
      return parent.booksubdepartment.map(subDept => ({
        ...subDept,
        departmentID: subDept.departmentID || parent.id,
      }));
    },
  },
  Book: {
    // 为Book生成唯一ID（示例数据无该字段，类型定义要求返回）
    id: (parent) => `${parent.subdepartmentId}-${parent.bookTitle.toLowerCase().replace(/\s+/g, '-')}`,
  },
};

4. 完整Apollo Server启动代码 #

将类型定义、数据源和Resolver整合，实现完整的服务器启动逻辑：

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

// 类型定义
const typeDefs = `
type Bookdepartment {
  id: ID
  booksubdepartment: [Booksubdepartment]
}

type Booksubdepartment {
  id: ID
  departmentID: String
  books: [Book]
}

type Book {
  id: ID
  subdepartmentId: String
  bookTitle: String
}

type Query {
  bookdepartments: [Bookdepartment]
}
`;

// 模拟数据源（同上）
const mockData = {
  department: [
    {
      "id": "123",
      "booksubdepartment": [
        {
          "id": "111",
          "departmentID": "123",
          "books": [
            {
              "subdepartmentId":"111",
              "bookTitle": "Book One on sub department 111"
            },
            {
              "subdepartmentId":"111",
              "bookTitle": "Book Two on sub department 111"
            }
          ]
        },
        {
          "id": "222",
          "books": [
            {
              "subdepartmentId":"222",
              "bookTitle": "Book one on sub department 222"
            },
            {
              "subdepartmentId":"222",
              "bookTitle": "Book two on sub department 222"
            }
          ]
        }
      ]
    },
    {
      "id": "345",
      "booksubdepartment": [
        {
          "id": "333",
          "departmentID": "345",
          "books": [
            {
              "subdepartmentId":"333",
              "bookTitle": "Book one on sub department 333"
            },
            {
              "subdepartmentId":"333",
              "bookTitle": "Book two on sub department 333"
            }
          ]
        },
        {
          "id": "444",
          "books": [
            {
              "subdepartmentId":"444",
              "bookTitle": "Book one on sub department 444"
            },
            {
              "subdepartmentId":"444",
              "bookTitle": "Book two on sub department 444"
            }
          ]
        }
      ]
    }
  ]
};

// Resolver实现（同上）
const resolvers = {
  Query: {
    bookdepartments: () => mockData.department,
  },
  Bookdepartment: {
    booksubdepartment: (parent) => {
      return parent.booksubdepartment.map(subDept => ({
        ...subDept,
        departmentID: subDept.departmentID || parent.id,
      }));
    },
  },
  Book: {
    id: (parent) => `${parent.subdepartmentId}-${parent.bookTitle.toLowerCase().replace(/\s+/g, '-')}`,
  },
};

// 启动服务器
async function startServer() {
  const server = new ApolloServer({
    typeDefs,
    resolvers,
  });

  const { url } = await startStandaloneServer(server, {
    listen: { port: 4000 },
  });

  console.log(`🚀 服务器运行在: ${url}`);
}

startServer();

5. 使用说明 #

1. 安装依赖：

npm install @apollo/server graphql

2. 运行代码，访问http://localhost:4000打开Apollo Sandbox
3. 执行以下查询：

query GetBookDepartments {
  bookdepartments {
    id
    booksubdepartment {
      id
      departmentID
      books {
        id
        subdepartmentId
        bookTitle
      }
    }
  }
}

即可得到符合类型定义的完整结果，包括补全的departmentID和自动生成的Book的id。

内容的提问来源于stack exchange，提问作者erwin