API Gateway的正文模板在映射时如何保留数据元素的有效JSON数据结构，同时仍允许base64-encoding?

Question

【以下的问题经过翻译处理】 我们目前正在根据该文档来创建面向Amazon Kinesis的（http://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-kinesis.html#api-gateway-get-and-add-records-to-stream）
客户想要在使用PutRecord和PutRecords API时支持以下载荷结构（数据元素须以json格式传递）：
{
    "records": [
        {
            "data": ,
            "PartitionKey": 
        },
        {
            "data": ,
            "PartitionKey": 
        }
    ]
}
例如：
{
    "records": [
        {
            "data": {
                "Events": [
                    {"DSType":"RTDS","DSInstance":"Unit 1","DSPoint":"Tag 1","TimeStamp":"2017-10-10T11:10:00.0000000+02:00","Value":8.0,"Quality":192},
                    {"DSType":"RTDS","DSInstance":"Unit 2","DSPoint":"Tag 2","TimeStamp":"2017-10-10T11:10:00.0000000+02:00","Value":7.0,"Quality":193}
                    ],
                    "Project":"EventAcquisitionStream",
                    "Plant":"Plant1"
            },
            "partition-key": "some key"
        },
        {
            "data": {
                "Events": [
                    {"DSType":"RTDS","DSInstance":"Unit 3","DSPoint":"Tag 3","TimeStamp":"2017-10-11T11:10:00.0000000+02:00","Value":8.0,"Quality":192},
                    {"DSType":"RTDS","DSInstance":"Unit 4","DSPoint":"Tag 4","TimeStamp":"2017-10-10T11:10:00.0000000+02:00","Value":7.0,"Quality":193}
                    ],
                    "Project":"EventAcquisitionStream",
                    "Plant":"Plant2"
            },
            "partition-key": "some key"
        }
    ]
}
根据AWS文档中的说明，我们为PutRecords模型配置了如下载荷模型以及请求模版：
模型：
{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "title": "PutRecords proxy payload data model",
  "type": "object",
  "properties": {
    "records": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "data": { 
              "type": "object",
              "properties": {
                "events": { 
                    "type": "array",
                    "items": {
                        "type": "object",
                        "properties": {
                            "dstype": { "type": "string" },
                            "dsinstance": { "type": "string" },
                            "dspoint": { "type": "string" },
                            "timeStamp": { "type": "string" },
                            "value": { "type": "number" },
                            "quality": { "type": "integer" }
                        }
                    }
                },
                "project": { "type": "string" },
                "plant": { "type": "string" }
              }
            },
          "partition-key": { "type": "string" }
        }
      }
    }
  }
}
正文模版映射：
{
    "StreamName": "$input.params('stream-name')",
    "Records": [
       #foreach($elem in $input.path('$.records'))
          {
            "Data": "$util.base64Encode($elem.data)",
            "PartitionKey": "$elem.partition-key"
          }#if($foreach.hasNext),#end
        #end
    ]
}
问题是，在该结构在kineses接收端被解码后，$elem.data中的内容会被转码成无效的json，比如在Events，Project，Planet元素中将: 替换成=后使得json无效：
Decoded payload: {Events=[{"DSType":"RTDS","DSInstance":"Unit 1","DSPoint":"Tag 1","TimeStamp":"2017-10-10T11:10:00.0000000+02:00","Value":8.0,"Quality":192},{"DSType":"RTDS","DSInstance":"Unit 2","DSPoint":"Tag 2","TimeStamp":"2017-10-10T11:10:00.0000000+02:00","Value":7.0,"Quality":193}], Project=EventAcquisitionStream, Plant=Plant1}
请问我该怎么配置我的请求正文映射模版以保证json数据结构有效，与此同时允许base64编码机制？

Answer

【以下的回答经过翻译处理】 请参考如下方案：
{ "StreamName": "event-stream-qa", "Records": [
#set($datakey = ".data")
#set($partitionkey = ".key")
#foreach($elem in $input.path('$.records'))
    #set($pathBegin = "$.records[")
    #set($pathEnd = "]")
    #set($currentIndex = $foreach.index)
    #set($dataPath = "$pathBegin$currentIndex$pathEnd$datakey")
    #set($partitionPath = "$pathBegin$currentIndex$pathEnd$partitionkey")
    #set($dataJson = $input.json($dataPath)) 
    #set($partitionJson = $input.json($partitionPath)) 
  { 
    "Data": "$util.base64Encode($dataJson)",
    "PartitionKey": $partitionJson
  }
    #if($foreach.hasNext),#end
#end  
  ]
}

API Gateway的正文模板在映射时如何保留数据元素的有效JSON数据结构，同时仍允许base64-encoding?

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