仅当变量具有值时，才在 DataWeave 中筛选变量的值，否则忽略过滤器

Question

在我的应用程序中，一些查询参数是可选的。我将这些查询参数存储在变量中。

我想使用这些变量来过滤带有DataWeave的对象。如果没有传入查询参数并且变量为 null 或不存在，则需要返回所有对象，因此无需过滤。

让我们以传入的能量类型参数为例。存储在流量变量中：energytypeVar（值可以是"gas"，"电力"，"水"）

应用于底部对象的过滤器：filter $.attributes.energyType == flowVars.energytypeVar

我尝试了各种条件逻辑方法，何时/否则仅在提供实际值时进行过滤。否则我根本不希望执行过滤器，因此返回所有对象。当变量没有有效的"energyType"时，完整的数据对象为空。

DW 脚本

%dw 1.0
%output application/json
%var resourceUrl="https://hostname/devices"
%var collectionSize = sizeOf payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult
---
{
meta:{code: 200, timestamp: now},
data: payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult map {
        type: "device",
        id: $.EnergyDeviceId,
        attributes: {
        energyType: $.EnergyType,
        deviceModel: $.HWModel,
        serialNumber: $.SerialNumber,
        name: $.Name,
        applianceType: $.applianceType,
        isCentralMeter: $.IsCentralMeter as :boolean,
        isSwitchable: $.IsSwitchable as :boolean,
        isOnline: $.IsOnline as :boolean,
        isProducer: $.IsProducer as :boolean,
        isSwitchedOn: $.IsSwitchedOn as :boolean,
        isLiveUsageEnabled: $.IsLiveUsageEnabled as :boolean,
        index: {
                value: $.MeterIndexValue,
                unit: 'm3' unless $.EnergyType == "electricity" otherwise "Wh",
                timestamp: $.MeterIndexTimestamp
                } when ($.IsCentralMeter == "true") otherwise null  
    },
    links: {
        self: resourceUrl ++ '/' ++ $.EnergyDeviceId
    }
} filter $.attributes.energyType == flowVars.energytypeVar
}

一个接一个的解决方案（应用了额外的过滤）

%dw 1.0
%output application/json
%var resourceUrl="https://hostname/devices"
%var collectionSize = sizeOf payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult
---
using (result = payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult map {
        type: "device",
        id: $.EnergyDeviceId,
        attributes: {
        energyType: $.EnergyType,
        deviceModel: $.HWModel,
        serialNumber: $.SerialNumber,
        name: $.Name,
        applianceType: $.applianceType,
        isCentralMeter: $.IsCentralMeter as :boolean,
        isSwitchable: $.IsSwitchable as :boolean,
        isOnline: $.IsOnline as :boolean,
        isProducer: $.IsProducer as :boolean,
        isSwitchedOn: $.IsSwitchedOn as :boolean,
        isLiveUsageEnabled: $.IsLiveUsageEnabled as :boolean,
        index: {
                value: $.MeterIndexValue,
                unit: 'm3' unless $.EnergyType == "electricity" otherwise "Wh",
                timestamp: $.MeterIndexTimestamp
                } when ($.IsCentralMeter == "true") otherwise null  
    },
    links: {
        self: resourceUrl ++ '/' ++ $.EnergyDeviceId
    }
})
{
meta:{code: 200, timestamp: now},
data: result filter ($.id == flowVars.deviceId) when (flowVars.deviceId != 0) otherwise {
data: result filter ($.attributes.energyType == flowVars.energyType) when flowVars.energyType != 0
otherwise result 
} distinctBy $.data
}

Answer 1

请尝试这个。

            %dw 1.0
        %output application/json
        %var resourceUrl="https://hostname/devices"
        %var collectionSize = sizeOf payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult
        ---
        {
        meta:{code: 200, timestamp: now},
        data: (payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult map {
                type: "device",
                id: $.EnergyDeviceId,
                attributes: {
                energyType: $.EnergyType,
                deviceModel: $.HWModel,
                serialNumber: $.SerialNumber,
                name: $.Name,
                applianceType: $.applianceType,
                isCentralMeter: $.IsCentralMeter as :boolean,
                isSwitchable: $.IsSwitchable as :boolean,
                isOnline: $.IsOnline as :boolean,
                isProducer: $.IsProducer as :boolean,
                isSwitchedOn: $.IsSwitchedOn as :boolean,
                isLiveUsageEnabled: $.IsLiveUsageEnabled as :boolean,
                index: {
                        value: $.MeterIndexValue,
                        unit: 'm3' unless $.EnergyType == "electricity" otherwise "Wh",
                        timestamp: $.MeterIndexTimestamp
                        } when ($.IsCentralMeter == "true") otherwise null  
            },
            links: {
                self: resourceUrl ++ '/' ++ $.EnergyDeviceId
            }
        } filter $.attributes.energyType == flowVars.energytypeVar) when flowVars.energytypeVar? otherwise (payload.Envelope.Body.GetEnergyDevicesResponse.GetEnergyDevicesResult map {
                type: "device",
                id: $.EnergyDeviceId,
                attributes: {
                energyType: $.EnergyType,
                deviceModel: $.HWModel,
                serialNumber: $.SerialNumber,
                name: $.Name,
                applianceType: $.applianceType,
                isCentralMeter: $.IsCentralMeter as :boolean,
                isSwitchable: $.IsSwitchable as :boolean,
                isOnline: $.IsOnline as :boolean,
                isProducer: $.IsProducer as :boolean,
                isSwitchedOn: $.IsSwitchedOn as :boolean,
                isLiveUsageEnabled: $.IsLiveUsageEnabled as :boolean,
                index: {
                        value: $.MeterIndexValue,
                        unit: 'm3' unless $.EnergyType == "electricity" otherwise "Wh",
                        timestamp: $.MeterIndexTimestamp
                        } when ($.IsCentralMeter == "true") otherwise null  
            },
            links: {
                self: resourceUrl ++ '/' ++ $.EnergyDeviceId
            }
        })
        }

希望这有帮助。