Accessing json array in AWS AppSync

Question

I am new to AWS AppSync and am trying to use an HTTP endpoint to fetch data from an external API. Here is an example of what that API returns.

{
  "status": 1,
  "size": 3,
  "result": [
    {
      "number": "123",
      "program": "program name",
      "team_name": "team name",
      "robot_name": "robot name",
      "organisation": "team organization",
      "city": "team city",
      "region": "team state",
      "country": "team country",
      "grade": "team grade",
      "is_registered": 0
    },
    {
      "number": "456",
      "program": "program name",
      "team_name": "team name",
      "robot_name": "robot name",
      "organisation": "team organization",
      "city": "team city",
      "region": "team state",
      "country": "team country",
      "grade": "team grade",
      "is_registered": 0
    },
    {
      "number": "789",
      "program": "program name",
      "team_name": "team name",
      "robot_name": "robot name",
      "organisation": "team organization",
      "city": "team city",
      "region": "team state",
      "country": "team country",
      "grade": "team grade",
      "is_registered": 0
    }
  ]
}

Here is my GraphQL Schema

type Query {
    getTeams(number: String!): Team
}

type Team {
    number: String
    program: String
    teamName: String
    robotName: String
    organization: String
    city: String
    region: String
    country: String
    grade: String
    isRegistered: Int
}

schema {
    query: Query
}

Here is my request mapping template

{
    "version": "2018-05-29",
    "method": "GET",
    "resourcePath": "/v1/get_teams",
    "params":{
        "query": {
            "APIKEY": "API_KEY_GOES_HERE"
        },
        "headers": {
            "Content-Type": "application/json"
        }
    }
}

And here is my response mapping template

#if($context.result.statusCode == 200)
## Success - decode the body and reconstruct the response with the schema in mind
#set($response = $util.parseJson($context.result.body))

#set($result = {
 "number": $response.result[0].number,
 "program": $response.result[0].program,
 "teamName": $response.result[0].team_name,
 "robotName": $response.result[0].robot_name,
 "organization": $response.result[0].organisation,
 "city": $response.result[0].city,
 "region": $response.result[0].region,
 "country": $response.result[0].country,
 "grade": $response.result[0].grade,
 "isRegistered": $response.result[0].is_registered
})
$util.toJson($result)
#else
## Error - send the proper error message
$utils.appendError($ctx.result.body, $ctx.result.statusCode)
#end

What I have currently worked but only returns one team. My question is how can I get the GraphQL query to return an array of teams by getting all of the items from the result array in the JSON file?

Jaime S · Accepted Answer · 2020-02-12 21:23:55Z

1

I'm not sure if I really understood what you are trying to achieve but here it goes:

If you want to return an array of teams instead of a single team, you have to modify your query in the schema as follow:

type Query {
    getTeams: [Team]
}

Now on the response mapping you can map directly the response to your array:

#if($ctx.result.statusCode == 200)
    ## If response is 200, return the body.
    $util.toJson($util.parseJson($ctx.result.body).result)
#else
    ## If response is not 200, append the response to error block.
    $utils.appendError($ctx.result.body, "$ctx.result.statusCode")
#end

At this point I noticed that you renamed the fields in your schema so it does not match anymore; for example your json is returning team_name but your graphQL schema is expecting teamName.

What I would do is to modify the schema to match with the JSON as follow:

type Team {
    number: String
    program: String
    team_name: String
    robot_name: String
    organisation: String
    city: String
    region: String
    country: String
    grade: String
    is_registered: Int
}

And then use alias in the query to return the fields with the expected name, for example:

query{
  getTeams{
    number: number
    teamName:team_name
    robotName: robot_name
    organization: organisation
  }
}

That will produce the output that I think that you are expecting:

{
  "data": {
    "getTeams": [
      {
        "number": "123",
        "teamName": "team name",
        "robotName": "robot name",
        "organization": "team organization"
      },
      ....

answered Feb 12, 2020 at 21:23

Jaime S

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3 Comments

Austin Robinson Over a year ago

If I were to have another similar to this such as getting events. I know how to get the JSON to graphql now but the events API returns info about an event, such as the event number. It doesn't return info on what teams will be at an event. But I can pass the event number to the team's API to get teams at that event. How can I use the retrieved event number and use that as a parameter in the team's request mapping template?

Jaime S Over a year ago

@AustinRobinson If you want to combine data from different resolvers or use the output of one resolver as input of other resolver you can use pipeline resolvers (docs.aws.amazon.com/appsync/latest/devguide/…)

Nurzhan Nogerbek Over a year ago

Hello guys! I have a very similar case. In my case, the AWS Lambda function returns JSON with the snake_case keys. At the same time, I would like to leave the camelCase keys for the fields in the GraphQL schema. Is it possible to achieve this by changing only the ResponseMappingTemplate in AppSync?

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