Lambda 函数 GraphQL 解析器

2025-06-04

Lambda 函数 GraphQL 解析器

Amplify CLI最近添加了对直接从 Amplify 环境为 AppSync API 部署 Lambda GraphQL 解析器的支持。Lambda 函数解析器允许您使用 JavaScript 编写 AppSync 解析器逻辑。

使用该@function指令，您可以指定与 GraphQL 架构中的 Lambda 函数交互的操作：



type Mutation {
  addEntry(id: Int, email: String): String @function(name: "addEntry-${env}")
}
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在本教程中，我将教您如何创建使用两种类型的 Lambda 解析器的应用程序：

  1. Lambda 解析器与另一个 API 对话并通过查询返回 GraphQL 响应

  2. Lambda 解析器发送查询和变异以与真实的 NoSQL 数据库交互来对其执行创建和读取操作。

在本教程结束时，您应该了解如何使用 Amplify Framework 部署与 Lambda GraphQL 解析器交互的 AppSync GraphQL API。

要查看该项目的最终源代码，请单击此处。

入门

首先，您需要创建一个新的 React 应用程序并在其中初始化一个新的 Amplify 项目：



npx create-react-app gql-lambda

cd gql-lambda

amplify init

# Follow the steps to give the project a name, environment name, and set the default text editor.
# Accept defaults for everything else and choose your AWS Profile.
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如果您尚未安装和配置 Amplify CLI，请按照此处的说明进行操作。

接下来，安装 AWS Amplify 库：



npm install aws-amplify
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创建 API

我们将创建的第一个 GraphQL API 将从另一个 REST API 查询数据并返回 GraphQL 响应。您将与之交互的 API 是Coinlore API。

让我们首先创建函数：



amplify add function

? Provide a friendly name for your resource to be used as a label for this category in the project: currencyfunction
? Provide the AWS Lambda function name: currencyfunction
? Choose the function runtime that you want to use: NodeJS
? Choose the function template that you want to use: Hello world
? Do you want to access other resources created in this project from your Lambda function? N
? Do you want to invoke this function on a recurring schedule? N
? Do you want to edit the local lambda function now? Y
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使用以下代码更新该函数：



// amplify/backend/function/currencyfunction/src/index.js
const axios = require('axios')

exports.handler = function (event, _, callback) {
  let apiUrl = `https://api.coinlore.com/api/tickers/?start=1&limit=10`

  if (event.arguments) { 
    const { start = 0, limit = 10 } = event.arguments
    apiUrl = `https://api.coinlore.com/api/tickers/?start=${start}&limit=${limit}`
  }

  axios.get(apiUrl)
    .then(response => callback(null, response.data.data))
    .catch(err => callback(err))
}
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在上面的函数中，我们使用了axios库来调用另一个 API。为了使用 axios，我们需要在函数文件夹中安装它。我们还会安装它uuid以供稍后使用：



cd amplify/backend/function/currencyfunction/src

npm install axios uuid

cd ../../../../../
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现在函数已经创建完成，我们需要创建 GraphQL API。为此，请运行 Amplifyadd命令：



amplify add api

? Please select from one of the below mentioned services: GraphQL
? Provide API name: currencyapi
? Choose an authorization type for the API: API key
? Enter a description for the API key: public
? After how many days from now the API key should expire (1-365): 365 (or your preferred expiration)
? Do you want to configure advanced settings for the GraphQL API: N
? Do you have an annotated GraphQL schema? N
? Do you want a guided schema creation? Y
? What best describes your project: Single object with fields
? Do you want to edit the schema now? Y
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接下来，在amplify/backend/api/currencyapi/schema.graphql中，使用以下内容更新架构：



type Coin {
  id: String!
  name: String!
  symbol: String!
  price_usd: String!
}

type Query {
  getCoins(limit: Int start: Int): [Coin] @function(name: "currencyfunction-${env}")
}
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现在 API 和 Lambda 函数都已创建。要部署并上线，您可以运行以下push命令：



amplify push

Current Environment: dev

| Category | Resource name    | Operation | Provider plugin   |
| -------- | -------------    | --------- | ----------------- |
| Api      | currencyapi      | Create    | awscloudformation |
| Function | currencyfunction | Create    | awscloudformation |
? Are you sure you want to continue? (Y/n) Y
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现在，资源已部署完毕，您可以尝试查询了！您可以在 AWS AppSync 控制台中测试查询。要打开 API 仪表板，请在终端中运行以下命令：



amplify console api

? Please select from one of the below mentioned services: GraphQL
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在查询编辑器中，运行以下查询：



# basic request
query listCoins {
  getCoins {
    price_usd
    name
    id
    symbol
  }
}

# request with arguments
query listCoinsWithArgs {
  getCoins(limit:3 start: 10) {
    price_usd
    name
    id
    symbol
  }
}
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此查询应返回加密货币信息数组。

更新 API 以针对 NoSQL 数据库执行 CRUD 操作

现在基本 API 已启动并运行，让我们创建一个数据库并更新 API 以对其执行创建和读取操作。

首先，我们将创建数据库：



amplify add storage

? Please select from one of the below mentioned services: NoSQL Database
? Please provide a friendly name for your resource that will be used to label this category in the project: currencytable
? Please provide table name: currencytable
? What would you like to name this column: id
? Please choose the data type: string
? Would you like to add another column? Y
? What would you like to name this column: name
? Please choose the data type: string
? Would you like to add another column? Y
? What would you like to name this column: symbol
? Please choose the data type: string
? Would you like to add another column? Y
? What would you like to name this column: price_usd
? Please choose the data type: string
? Would you like to add another column? N
? Please choose partition key for the table: id
? Do you want to add a sort key to your table? N
? Do you want to add global secondary indexes to your table? N
? Do you want to add a Lambda Trigger for your Table? N
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接下来，让我们更新函数以使用新的数据库。



amplify update function

? Please select the Lambda Function you would want to update: currencyfunction
? Do you want to update permissions granted to this Lambda function to perform on other resources in your project? Y
? Select the category: storage
? Select the operations you want to permit for currencytable:
  ◉ create
  ◉ read
  ◉ update
 ❯◉ delete
? Do you want to invoke this function on a recurring schedule? N
? Do you want to edit the local lambda function now? Y
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接下来，我们将更新 lambda 函数。目前，该函数代码仅位于一个文件index.js中，该文件位于amplify/backend/function/currencyfunction/src/index.js。在src文件夹中，创建两个新文件：createCoin.js和getCoins.js。在接下来的步骤中，我们将更新index.js，并在另外两个新文件中填充代码。

index.js



const getCoins = require('./getCoins')
const createCoin = require('./createCoin')

exports.handler = function (event, _, callback) {
  if (event.typeName === 'Mutation') {
    createCoin(event, callback)
  }
  if (event.typeName === 'Query') {
    getCoins(callback)
  }
}
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在函数的参数中event，有一个typeName字段会告诉我们该操作是 Mutation 还是 Query。如果有多个 Queries 或 Mutation，还有一个fieldName参数会告诉你实际执行的字段。

我们将使用该字段根据操作类型typeName来调用createCoin或。getCoins

getCoins.js



const AWS = require('aws-sdk')
const region = process.env.REGION
const storageCurrencytableName = process.env.STORAGE_CURRENCYTABLE_NAME
const docClient = new AWS.DynamoDB.DocumentClient({region})

const params = {
  TableName: storageCurrencytableName
}

function getCoins(callback) {
  docClient.scan(params, function(err, data) {
    if (err) {
      callback(err)
    } else {
      callback(null, data.Items)
    }
  });
}

module.exports = getCoins
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在getCoins中，我们调用 DynamoDBscan操作来读取数据库并返回数组中的所有值。我们还使用DynamoDB.DocumentClient sdk 来简化使用 JavaScript 处理 Amazon DynamoDB 中项目的操作。

createCoin.js



const AWS = require('aws-sdk')
const { v4: uuid } = require('uuid')
const region = process.env.REGION
const ddb_table_name = process.env.STORAGE_CURRENCYTABLE_NAME
const docClient = new AWS.DynamoDB.DocumentClient({region})

function write(params, event, callback){
  docClient.put(params, function(err, data) {
    if (err) {
      callback(err)
    } else {
      callback(null, event.arguments)
    }
  })
}

function createCoin(event, callback) {
  const args = { ...event.arguments, id: uuid() }
  var params = {
    TableName: ddb_table_name,
    Item: args
  };

  if (Object.keys(event.arguments).length > 0) {
    write(params, event, callback)
  } 
}

module.exports = createCoin
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在createCoin 函数中，我们通过传入的参数对 DynamoDB 表进行操作。我们还会在服务器上自动生成 ID，并使用uuidputItem库为项目填充唯一的 ID 。

最后，我们将更新amplify/backend/api/currencyapi/schema.graphql中的 GraphQL Schema以添加突变定义：



# amplify/backend/api/currencyapi/schema.graphql

type Coin {
  id: String!
  name: String!
  symbol: String!
  price_usd: String!
}

type Query {
  getCoins(limit: Int start: Int): [Coin] @function(name: "currencyfunction-${env}")
}

# new mutation definition
type Mutation {
  createCoin(name: String! symbol: String! price_usd: String!): Coin @function(name: "currencyfunction-${env}")
}
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现在，部署更改：



amplify push
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测试一下

现在，资源已部署完毕，您可以尝试查询了！您可以在 AWS AppSync 控制台中测试查询。要打开您的项目，请在终端中运行以下命令：



amplify console api

? Please select from one of the below mentioned services: GraphQL
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测试以下查询：



query listCoins {
  getCoins {
    price_usd
    name
    id
    symbol
  }
}

mutation createCoin {
  createCoin(
    name: "Monero"
    price_usd: "86.85"
    symbol: "XMR"
  ) {
    name price_usd symbol
  }
}
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在客户端上测试

如果您想在 React 应用程序中测试它，您可以使用APIAmplify 中的类别：



import { API, graphqlOperation } from 'aws-amplify'
import { getCoins } from './graphql/queries'
import { createCoin } from './graphql/mutations'

// mutation
const coin = { name: "Bitcoin", symbol: "BTC", price: "10000" }
API.graphql(graphqlOperation(createCoin, coin))
  .then(data => console.log({ data }))
  .catch(err => console.log('error: ', err))

// query
API.graphql(graphqlOperation(getCoins))
  .then(data => console.log({ data }))
  .catch(err => console.log('error: ', err))
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要查看该项目的最终源代码，请单击此处。

文章来源：https://dev.to/dabit3/lambda-function-graphql-resolvers-11cd
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