欄位遮罩

在 Google Ads API 中，更新作業是使用欄位遮罩完成。欄位遮罩 (google.protobuf.FieldMask) 包含 snake_case 中要透過更新變更的欄位路徑清單。即使傳送至伺服器，系統也會忽略未列在欄位遮罩中的任何指定欄位。

FieldMasks 公用程式

在 Java 用戶端程式庫中，建議使用內建的 FieldMasks 公用程式類別產生欄位遮罩，這樣就能從修改過的物件產生欄位遮罩，不必從頭建構。

以下是更新廣告活動的範例：

// Creates a Campaign object with the proper resource name and any other
// changes.
Campaign campaign =
    Campaign.newBuilder()
        .setResourceName(ResourceNames.campaign(customerId, campaignId))
        .setStatus(CampaignStatus.PAUSED)
        .build();

// Constructs an operation that updates the campaign, using the
// FieldMasks.allSetFieldsOf utility to derive the update mask. This mask tells
// the Google Ads API which attributes of the campaign you want to change.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(FieldMasks.allSetFieldsOf(campaign))
        .build();

// Sends the operation in a mutate request.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

這個範例會先建立空白的 Campaign 建構工具，並設定資源名稱，讓 API 知道要更新哪個廣告活動。

接著，範例會對廣告活動呼叫 FieldMasks.allSetFieldsOf()，自動產生列舉所有已設定欄位的欄位遮罩。您可以將傳回的遮罩直接傳遞至更新呼叫。

如要使用現有物件並更新幾個欄位，請按照下列方式使用 FieldMasks.compare()：

// Assumes existingCampaign was retrieved from a previous API call.

// Creates a new campaign based on the existing campaign and updates the
// campaign by setting its status to paused.
Campaign campaignToUpdate =
    existingCampaign.toBuilder()
        .setStatus(CampaignStatus.PAUSED)
        .build();

// Constructs an operation that updates the campaign, using the
// FieldMasks.compare utility to derive the update mask. This mask tells the
// Google Ads API which attributes of the campaign you want to change.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaignToUpdate)
        .setUpdateMask(FieldMasks.compare(existingCampaign, campaignToUpdate))
        .build();

// Sends the operation in a mutate request.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

如要從頭建立欄位遮罩，請建立 FieldMask 建構工具，並新增要變更的每個欄位 snake_case 名稱：

FieldMask fieldMask =
    FieldMask.newBuilder()
        .addPaths("status")
        .addPaths("name")
        .build();

更新訊息欄位及其子欄位

MESSAGE 欄位可以有子欄位 (例如 MaximizeConversions，其中包含 target_cpa_micros、cpc_bid_ceiling_micros 和 cpc_bid_floor_micros)，也可以沒有子欄位 (例如 ManualCpm)。

未定義子欄位的訊息欄位

更新未定義任何子欄位的 MESSAGE 欄位時，請使用 FieldMasks 公用程式產生欄位遮罩，如上一節所述。

含有已定義子欄位的訊息欄位

更新已定義子欄位的 MESSAGE 欄位時，如果未在該訊息中明確設定任何子欄位，則必須手動將每個可變動 MESSAGE 子欄位新增至 FieldMask，類似於從頭建立欄位遮罩。

常見例子是更新廣告活動的出價策略 (oneof 欄位 campaign_bidding_strategy)，但未設定新出價策略的任何欄位。以下範例說明如何更新廣告活動，以使用 MaximizeConversions 出價策略，而不設定出價策略的任何子欄位。

在這種情況下，單獨使用 FieldMasks 的 allSetFieldsOf() 和 compare() 方法無法達到預期目標。

以下範例會產生包含 maximize_conversions 的欄位遮罩。不過，Google Ads API 不允許更新遮罩中含有子欄位的頂層訊息路徑 (避免不小心清除子欄位)，並會傳回 FieldMaskError.FIELD_HAS_SUBFIELDS 錯誤。

警告： 下列程式碼會產生 FieldMaskError.FIELD_HAS_SUBFIELDS 錯誤。

// Creates a campaign with the proper resource name and an empty
// MaximizeConversions field.
Campaign campaign =
    Campaign.newBuilder()
        .setResourceName(ResourceNames.campaign(customerId, campaignId))
        .setMaximizeConversions(MaximizeConversions.newBuilder().build())
        .build();

// Constructs an operation using FieldMasks.allSetFieldsOf to derive the update
// mask. The field mask includes 'maximize_conversions', which produces a
// FieldMaskError.FIELD_HAS_SUBFIELDS error.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(FieldMasks.allSetFieldsOf(campaign))
        .build();

// Sends the operation in a mutate request that results in a
// FieldMaskError.FIELD_HAS_SUBFIELDS error because empty MESSAGE fields with
// subfields cannot be included directly in a field mask.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

以下範例說明如何正確更新廣告活動，以使用 MaximizeConversions 出價策略，而不設定任何子欄位。進一步瞭解如何指派標準和組合出價策略。

成功： 下列程式碼會更新廣告活動出價策略，不會發生錯誤。

// Creates a Campaign object with the proper resource name.
Campaign campaign =
    Campaign.newBuilder()
        .setResourceName(ResourceNames.campaign(customerId, campaignId))
        .build();

// Creates a field mask from the campaign and adds the mutable subfield
// ('maximize_conversions.target_cpa_micros') on the MaximizeConversions
// bidding strategy to the field mask. Because this subfield is included in the
// field mask while excluded from the campaign object, the Google Ads API
// switches the campaign's bidding strategy oneof to MaximizeConversions with
// target_cpa_micros unset.
FieldMask fieldMask =
    FieldMasks.allSetFieldsOf(campaign).toBuilder()
        .addPaths("maximize_conversions.target_cpa_micros")
        .build();

// Creates an operation to update the campaign with the specified fields.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(fieldMask)
        .build();

清除欄位

部分欄位可以明確清除。與前例類似，您必須明確將這些欄位新增至欄位遮罩，同時在訊息物件上不設定這些欄位。舉例來說，假設您有一個廣告活動採用 MaximizeConversions 出價策略，且 target_cpa_micros 欄位的值大於 0。

下列程式碼會執行，但 maximize_conversions.target_cpa_micros 不會如預期清除：

警告： 這段程式碼不會清除 MaximizeConversions 出價策略的 target_cpa_micros。

// Creates a campaign with the proper resource name and a MaximizeConversions
// object with target_cpa_micros set to 0L.
Campaign campaign =
    Campaign.newBuilder()
        .setResourceName(ResourceNames.campaign(customerId, campaignId))
        .setMaximizeConversions(
            MaximizeConversions.newBuilder().setTargetCpaMicros(0L).build())
        .setStatus(CampaignStatus.PAUSED)
        .build();

// Constructs an operation using FieldMasks.allSetFieldsOf to derive the
// update mask.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(FieldMasks.allSetFieldsOf(campaign))
        .build();

// Sends the operation in a mutate request that does not clear the field
// cleanly.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

下一個範例說明如何正確清除 MaximizeConversions 出價策略的 target_cpa_micros 欄位。

成功： 下列程式碼會清除 target_cpa_micros。

// Creates a Campaign object with the proper resource name.
Campaign campaign =
    Campaign.newBuilder()
        .setResourceName(ResourceNames.campaign(customerId, campaignId))
        .build();

// Constructs a field mask from the campaign and adds the
// 'maximize_conversions.target_cpa_micros' field to the field mask, which
// clears this field from the bidding strategy without impacting any other
// fields on the bidding strategy.
FieldMask fieldMask =
    FieldMasks.allSetFieldsOf(campaign).toBuilder()
        .addPaths("maximize_conversions.target_cpa_micros")
        .build();

// Creates an operation to update the campaign with the specified field.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(fieldMask)
        .build();

重點： 如要清除欄位，請在 FieldMask 中明確新增該欄位的路徑，並將資源物件上的欄位留空。