AppSync×DynamoDB（UPDATE編）

概要

AppSyncとDynamoDBを使用した簡易的なAPIの作成方法を紹介します。

この記事では、DBのデータを変更する処理を紹介します。

前提条件

• DynamoDBが用意されていること

AppSync

スキーマ

input CreateRadioInput {
  id: ID!
  program_name: String
  cast: [String!]
  weekday: Int
  time: String
  favorite: Boolean
}

type Mutation {
  createRadio(input: CreateRadioInput!): Radio
  updateRadio(input: UpdateRadioInput!): Radio # 今回追加する箇所
}

type Query {
  getRadio(id: ID!): Radio
  listRadio(filter: TableRadioFilterInput, limit: Int, nextToken: String): RadioConnection
}

type Radio {
  id: ID!
  program_name: String
  cast: [String!]
  weekday: Int
  time: String
  favorite: Boolean
}

type RadioConnection {
  items: [Radio]
  nextToken: String
}

input TableBooleanFilterInput {
  ne: Boolean
  eq: Boolean
}

input TableIntFilterInput {
  ne: Int
  eq: Int
  le: Int
  lt: Int
  ge: Int
  gt: Int
  contains: Int
  notContains: Int
  between: [Int]
}

input TableRadioFilterInput {
  day: TableIntFilterInput
  time: TableStringFilterInput
  favorite: TableBooleanFilterInput
}

input TableStringFilterInput {
  ne: String
  eq: String
  le: String
  lt: String
  ge: String
  gt: String
  contains: String
  notContains: String
  between: [String]
  beginsWith: String
}

# 今回追加する箇所
input UpdateRadioInput {
  id: ID!
  program_name: String
  cast: [String!]
  day: Int
  time: String
  favorite: Boolean
}

リゾルバー

• リゾルバーのQueryからupdateRadio(...): Radioのアタッチを選択

リクエストマッピングテンプレート

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

  ## 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, ["id"]).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(#id)",
    "expressionNames": {
      "#id": "id",
    },
  }
}

レスポンスマッピングテンプレート

$util.toJson($ctx.result)

実行

• クエリを実行する
  • 画面左が実行クエリ、画面右が実行結果
    
• DynamoDBのデータが変更されていることの確認