ChatGPTによるAWS Serverless Applicationチュートリアル

まず、プロジェクト用のディレクトリを作成し、その中に移動します。

“`bash
mkdir simple-todo-app
cd simple-todo-app
“`

次に、AWS SAM CLI を使用してバックエンド用のプロジェクトを初期化します。

“`bash
sam init –runtime nodejs14.x –name backend
cd backend
“`

`template.yaml` ファイルを開き、以下のように編集してください。

“`yaml
Resources:
TodosTable:
Type: AWS::DynamoDB::Table
Properties:
TableName: Todos
AttributeDefinitions:
– AttributeName: id
AttributeType: S
KeySchema:
– AttributeName: id
KeyType: HASH
ProvisionedThroughput:
ReadCapacityUnits: 5
WriteCapacityUnits: 5

GetTodosFunction:
Type: AWS::Serverless::Function
Properties:
CodeUri: src/
Handler: getTodos.handler
Runtime: nodejs14.x
Environment:
Variables:
TODOS_TABLE: !Ref TodosTable
Events:
GetTodosApi:
Type: Api
Properties:
Path: /todos
Method: GET

CreateTodoFunction:
Type: AWS::Serverless::Function
Properties:
CodeUri: src/
Handler: createTodo.handler
Runtime: nodejs14.x
Environment:
Variables:
TODOS_TABLE: !Ref TodosTable
Events:
CreateTodoApi:
Type: Api
Properties:
Path: /todos
Method: POST

UpdateTodoFunction:
Type: AWS::Serverless::Function
Properties:
CodeUri: src/
Handler: updateTodo.handler
Runtime: nodejs14.x
Environment:
Variables:
TODOS_TABLE: !Ref TodosTable
Events:
UpdateTodoApi:
Type: Api
Properties:
Path: /todos/{id}
Method: PUT

DeleteTodoFunction:
Type: AWS::Serverless::Function
Properties:
CodeUri: src/
Handler: deleteTodo.handler
Runtime: nodejs14.x
Environment:
Variables:
TODOS_TABLE: !Ref TodosTable
Events:
DeleteTodoApi:
Type: Api
Properties:
Path: /todos/{id}
Method: DELETE

Outputs:
TodosApi:
Description: API Gateway endpoint URL for the todos
Value: !Sub “https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/todos/”
TodosTable:
Description: DynamoDB table for storing todos
Value: !Ref TodosTable
“`

これにより、DynamoDB テーブルの作成と、各エンドポイントに対応する Lambda 関数が定義されます。

`src` ディレクトリに移動し、以下の JavaScript ファイルを作成して、それぞれの Lambda 関数のコードを実装します。
#### getTodos.js

“`javascript
const AWS = require(“aws-sdk”)
const dynamo = new AWS.DynamoDB.DocumentClient()

exports.handler = async (event) => {
const params = {
TableName: process.env.TODOS_TABLE,
}

const result = await dynamo.scan(params).promise()

return {
statusCode: 200,
body: JSON.stringify(result.Items),
}
}
“`

#### createTodo.js

“`javascript
const AWS = require(“aws-sdk”)
const dynamo = new AWS.DynamoDB.DocumentClient()
const uuid = require(“uuid”)

exports.handler = async (event) => {
const data = JSON.parse(event.body)

const params = {
TableName: process.env.TODOS_TABLE,
Item: {
id: uuid.v1(),
title: data.title,
details: data.details,
dueDate: data.dueDate,
completed: false,
},
}

await dynamo.put(params).promise()

return {
statusCode: 200,
body: JSON.stringify(params.Item),
}
}
“`

#### updateTodo.js

“`javascript
const AWS = require(“aws-sdk”)
const dynamo = new AWS.DynamoDB.DocumentClient()

exports.handler = async (event) => {
const data = JSON.parse(event.body)
const id = event.pathParameters.id

const params = {
TableName: process.env.TODOS_TABLE,
Key: {
id: id,
},
UpdateExpression:
“SET title = :title, details = :details, dueDate = :dueDate, completed = :completed”,
ExpressionAttributeValues: {
“:title”: data.title,
“:details”: data.details,
“:dueDate”: data.dueDate,
“:completed”: data.completed,
},
ReturnValues: “ALL_NEW”,
}

const result = await dynamo.update(params).promise()

return {
statusCode: 200,
body: JSON.stringify(result.Attributes),
}
}
“`

#### deleteTodo.js

“`javascript
const AWS = require(“aws-sdk”)
const dynamo = new AWS.DynamoDB.DocumentClient()

exports.handler = async (event) => {
const id = event.pathParameters.id

const params = {
TableName: process.env.TODOS_TABLE,
Key: {
id: id,
},
}

await dynamo.delete(params).promise()

return {
statusCode: 200,
body: JSON.stringify({message: “Todo deleted successfully”}),
}
}
“`

これでバックエンドの実装が完了しました。