Amazon web services 在不返回值的对象数组上使用VTL foreach循环

我使用AWSAPI网关作为restful API端点，然后将记录传递到Kinesis流，然后传递到Lambda。但是，似乎有一些数据未到达Lambda函数

我一直在到处寻找一个例子或接近我正在寻找的东西，但没有运气

设备消息的外观类似于以下内容，并且可以有多条消息，因此它位于数组中

[{
    "deviceId": "00000000001",
    "deviceType": "device",
    "receivedTs": 1539234374000,
    "readingList": [{
        "channelId": 13,
        "type": "temperature",
        "value": 25.3,
        "unit": "°C"
     },{
        "channelId": 12,
        "type": "humidity",
        "value": 3.65,
        "unit": "V",
       "label": "primary-battery"
     }]
}]

我目前拥有的传出映射模板如下：

{
    "StreamName": "my-stream",
    "Records": [
       #foreach($elem in $input.path('$'))
          #set($event =  "{
            ""deviceId"": $elem.deviceId
            ""deviceType"": $elem.deviceType,
            ""receivedTs"": $elem.receivedTs,
            ""readingList"": [
            #foreach($reading in $elem.readingList)
            {
                ""channelId"": $reading.channelId,
                ""type"": ""$reading.type"",
                ""value"": $reading.value,
                ""unit"": ""$reading.unit"",
                ""label"": ""$reading.label""
            }]
            #if($foreach.hasNext),#end
         #end            
         }")
     {
     "Data": "$util.base64Encode($event)",
     "PartitionKey": "$elem.deviceType"
     }#if($foreach.hasNext),#end
      #end
    ]
}

下面是我的CloudWatch日志从lambda函数内的处理中显示的内容。显示了一些数据，但对象的readingList数组没有正确填写，结果显示为空。我觉得这与映射模板中的foreach循环有关，但我似乎不知道是什么

Beginning to process all 1 records...
Event Name: aws:kinesis:record
Getting record contents.
Record contents: {
"deviceId": "00000000001",
"deviceType": "device",
"receivedTs": "1539234374000",
"readingList": [{
    "channelId": "",
    "type": "",
    "value": "",
    "unit": "",
    "label": ""
    }]
}

lambda函数没有什么特别之处。对于测试，它只是使用AWS提供的示例代码将消息内容写入控制台

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如果任何人有任何想法或一些有用的链接，将不胜感激。谢谢你抽出时间来。

好吧，我让它工作起来了。这与模板有关

{
    "StreamName": "my-stream",
    "Records": [
       #foreach($elem in $input.path('$'))
          #set($event =  "{
            ""deviceId"": $elem.deviceId,
            ""deviceType"": $elem.deviceType,
            ""receivedTs"": $elem.receivedTs,
            ""readingList"": [
            #foreach($reading in $elem.readingList)
            {
                ""channelId"": $reading.channelId,
                ""type"": ""$reading.type"",
                ""value"": $reading.value,
                ""unit"": ""$reading.unit"",
                ""label"": ""$reading.label""
            }
            #if($foreach.hasNext),#end
         #end
         ]           
     }")
     {
     "Data": "$util.base64Encode($event)",
     "PartitionKey": "$elem.deviceType"
     }#if($foreach.hasNext),#end
      #end
    ]
}

首先，我在$elem.deviceId后面缺少了一个逗号，readingList数组的右括号在foreach循环的结尾后面

错过那些愚蠢的错误，我一定是受够了