Using HTTP resolvers in AWS AppSync

Sets up a Lambda function that contains your business logic for your microservice.

Sets up an API Gateway REST API with the following endpoint/method/content type combination:

Open the AWS AppSync console and choose Create API.

Choose GraphQL APIs and then choose Design from scratch. Choose Next.

For the API name, type UserData. Choose Next.

Choose Create GraphQL resources later. Choose Next.

Review your inputs and choose Create API.

In the Data sources page in your AWS AppSync GraphQL API, choose Create data source.

Enter a name for the data source like HTTP_Example.

In Data source type, choose HTTP endpoint.

Set the endpoint to the API Gateway endpoint that was created at the beginning of the tutorial. You can find your stack-generated endpoint if you navigate to the Lambda console and find your application under Applications. Inside of your application's settings, you should see an API endpoint which will be your endpoint in AWS AppSync. Make sure you don’t include the stage name as part of the endpoint. For instance, if your endpoint were https://aaabbbcccd.execute-api.us-east-1.amazonaws.com/v1, you would type in https://aaabbbcccd.execute-api.us-east-1.amazonaws.com.

In your AWS AppSync GraphQL API, choose the Schema tab.

To the right of the Schema editor, in the Resolvers pane and under the Query type, find the getUser field and choose Attach.

Keep the resolver type to Unit and the runtime to APPSYNC_JS.

In Data source name, choose the HTTP endpoint you made earlier.

Choose Create.

In the Resolver code editor, add the following snippet as your request handler:

import { util } from '@aws-appsync/utils'

export function request(ctx) {
	return {
		version: '2018-05-29',
		method: 'GET',
		params: {
			headers: {
				'Content-Type': 'application/json',
			},
		},
		resourcePath: `/v1/users/${ctx.args.id}`,
	}
}

Add the following snippet as your response handler:

export function response(ctx) {
	const { statusCode, body } = ctx.result
	// if response is 200, return the response
	if (statusCode === 200) {
		return JSON.parse(body)
	}
	// if response is not 200, append the response to error block.
	util.appendError(body, statusCode)
}

Choose the Query tab, and then run the following query:

query GetUser{
    getUser(id:1){
        id
        username
    }
}

This should return the following response:

{
    "data": {
        "getUser": {
            "id": "1",
            "username": "nadia"
        }
    }
}

Choose the Schema tab.

To the right of the Schema editor, in the Resolvers pane and under the Query type, find the addUser field and choose Attach.

Keep the resolver type to Unit and the runtime to APPSYNC_JS.

In Data source name, choose the HTTP endpoint you made earlier.

Choose Create.

In the Resolver code editor, add the following snippet as your request handler:

export function request(ctx) {
    return {
        "version": "2018-05-29",
        "method": "POST",
        "resourcePath": "/v1/users",
        "params":{
            "headers":{
                "Content-Type": "application/json"
            },
        "body": ctx.args.userInput
        }
    }
}

Add the following snippet as your response handler:

export function response(ctx) {
    if(ctx.error) {
        return util.error(ctx.error.message, ctx.error.type)
    }
    if (ctx.result.statusCode == 200) {
        return ctx.result.body
    } else {
        return util.appendError(ctx.result.body, "ctx.result.statusCode")
    }
}

Choose the Query tab, and then run the following query:

mutation addUser{
    addUser(userInput:{
        id:"2",
        username:"shaggy"
    }){
        id
        username
    }
}

If you run the getUser query again, it should return the following response:

{
    "data": {
        "getUser": {
        "id": "2",
        "username": "shaggy"
        }
    }
}