概要

パーティションキーとソートキーが設定されているDynamoDBにつながっているAppSyncのリゾルバー記述方法を紹介します。

前提条件

DynamoDBにテーブルが用意されていること

AppSync

スキーマ

  input CreateRadioInput {
  	broadcaster: String!
  	program_name: String
  	cast: [String!]
  	datetime: String!
  	favorite: Boolean
  }
  
  input DeleteRadioInput {
  	broadcaster: String!
  	datetime: String!
  }
  
  type Mutation {
  	createRadio(input: CreateRadioInput!): Radio
  	updateRadio(input: UpdateRadioInput!): Radio
  	deleteRadio(input: DeleteRadioInput!): Radio
  }
  
  type Query {
  	getRadio(broadcaster: String!, datetime: String!): Radio
  }
  
  type Radio {
  	broadcaster: String!
  	program_name: String
  	cast: [String!]
  	datetime: String!
  	favorite: Boolean
  }
  
  input UpdateRadioInput {
  	broadcaster: String!
  	program_name: String
  	cast: [String!]
  	datetime: String!
  	favorite: Boolean
  }

リゾルバー

CREATE

  {
    "version": "2017-02-28",
    "operation": "PutItem",
    "key": {
      "broadcaster": $util.dynamodb.toDynamoDBJson($ctx.args.input.broadcaster),
      "datetime": $util.dynamodb.toDynamoDBJson($ctx.args.input.datetime),
    },
    "attributeValues": $util.dynamodb.toMapValuesJson($ctx.args.input),
    "condition": {
      "expression": "attribute_not_exists(#broadcaster) AND attribute_not_exists(#datetime)",
      "expressionNames": {
        "#broadcaster": "broadcaster",
        "#datetime": "datetime",
      },
    },
  }

READ

  {
    "version": "2017-02-28",
    "operation": "GetItem",
    "key": {
    "broadcaster": $util.dynamodb.toDynamoDBJson($ctx.args.broadcaster),
    "datetime": $util.dynamodb.toDynamoDBJson($ctx.args.datetime),
    },
  }

UPDATE

  {
    "version": "2017-02-28",
    "operation": "UpdateItem",
    "key": {
      "broadcaster": $util.dynamodb.toDynamoDBJson($ctx.args.input.broadcaster),
      "datetime": $util.dynamodb.toDynamoDBJson($ctx.args.input.datetime),
    },
  
    ## Set up some space to keep track of things we're updating **
    #set( $expNames  = {} )
    #set( $expValues = {} )
    #set( $expSet = {} )
    #set( $expAdd = {} )
    #set( $expRemove = [] )
  
    ## Iterate through each argument, skipping keys **
    #foreach( $entry in $util.map.copyAndRemoveAllKeys($ctx.args.input, ["broadcaster", "datetime"]).entrySet() )
      #if( $util.isNull($entry.value) )
        ## If the argument is set to "null", then remove that attribute from the item in DynamoDB **
  
        #set( $discard = ${expRemove.add("#${entry.key}")} )
        $!{expNames.put("#${entry.key}", "${entry.key}")}
      #else
        ## Otherwise set (or update) the attribute on the item in DynamoDB **
  
        $!{expSet.put("#${entry.key}", ":${entry.key}")}
        $!{expNames.put("#${entry.key}", "${entry.key}")}
        $!{expValues.put(":${entry.key}", $util.dynamodb.toDynamoDB($entry.value))}
      #end
    #end
  
    ## Start building the update expression, starting with attributes we're going to SET **
    #set( $expression = "" )
    #if( !${expSet.isEmpty()} )
      #set( $expression = "SET" )
      #foreach( $entry in $expSet.entrySet() )
        #set( $expression = "${expression} ${entry.key} = ${entry.value}" )
        #if ( $foreach.hasNext )
          #set( $expression = "${expression}," )
        #end
      #end
    #end
  
    ## Continue building the update expression, adding attributes we're going to ADD **
    #if( !${expAdd.isEmpty()} )
      #set( $expression = "${expression} ADD" )
      #foreach( $entry in $expAdd.entrySet() )
        #set( $expression = "${expression} ${entry.key} ${entry.value}" )
        #if ( $foreach.hasNext )
          #set( $expression = "${expression}," )
        #end
      #end
    #end
  
    ## Continue building the update expression, adding attributes we're going to REMOVE **
    #if( !${expRemove.isEmpty()} )
      #set( $expression = "${expression} REMOVE" )
  
      #foreach( $entry in $expRemove )
        #set( $expression = "${expression} ${entry}" )
        #if ( $foreach.hasNext )
          #set( $expression = "${expression}," )
        #end
      #end
    #end
  
    ## Finally, write the update expression into the document, along with any expressionNames and expressionValues **
    "update": {
      "expression": "${expression}",
      #if( !${expNames.isEmpty()} )
        "expressionNames": $utils.toJson($expNames),
      #end
      #if( !${expValues.isEmpty()} )
        "expressionValues": $utils.toJson($expValues),
      #end
    },
  
    "condition": {
      "expression": "attribute_exists(#broadcaster) AND attribute_exists(#datetime)",
      "expressionNames": {
        "#broadcaster": "broadcaster",
        "#datetime": "datetime",
      },
    }
  }

DELETE

  {
    "version": "2017-02-28",
    "operation": "DeleteItem",
    "key": {
      "broadcaster": $util.dynamodb.toDynamoDBJson($ctx.args.input.broadcaster),
      "datetime": $util.dynamodb.toDynamoDBJson($ctx.args.input.datetime),
    },
  }