字段掩码

在 Google Ads API 中，更新是使用字段掩码完成的。字段掩码会列出您打算通过更新更改的所有字段，并且系统会忽略字段掩码中未包含的任何指定字段，即使这些字段已发送到服务器也是如此。

FieldMaskUtil

生成字段掩码的推荐方法是使用我们的内置字段掩码实用程序，您可以通过该实用程序根据修改后的对象生成字段掩码，而无需从头构建。

下面是一个更新广告系列的示例：

// 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 will update 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));

此示例会先创建一个空的 Campaign 对象，然后设置其资源名称，以便 API 知道要更新哪个广告系列。

该示例对广告系列使用 FieldMasks.allSetFieldsOf() 方法，自动生成一个字段掩码，用于枚举所有已设置的字段。然后，您可以直接将返回的掩码传递给更新调用。

如果您需要使用现有对象更新一些字段，可以按如下方式修改代码：

Campaign existingCampaign;

// Obtains existingCampaign from elsewhere.
...

// Creates a new campaign based off 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 will update 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));

如需从头创建字段遮罩，您需要先创建一个 FieldMask 对象，然后将您打算更改的每个字段的名称添加到该对象。

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

更新消息字段及其子字段

MESSAGE 字段可以有子字段（例如 MaximizeConversions 有三个子字段：target_cpa_micros、cpc_bid_ceiling_micros 和 cpc_bid_floor_micros），也可以没有子字段（例如 ManualCpm）。

未定义子字段的消息字段

更新未使用任何子字段定义的 MESSAGE 字段时，请使用 FieldMaskUtil 生成字段掩码，如上所述。

包含已定义子字段的消息字段

更新使用子字段定义的 MESSAGE 字段时，如果未在该消息上明确设置任何子字段，则必须手动将每个可变 MESSAGE 子字段添加到 FieldMask，这与从头创建字段掩码的上例类似。

一个常见的示例是，更新广告系列的出价策略，但未在新的出价策略中设置任何字段。以下示例演示了如何更新广告系列以使用 MaximizeConversions 出价策略，而无需为出价策略设置任何子字段。

在本例中，使用 FieldMaskUtil 的 allSetFieldsOf() 和 compare() 方法无法实现预期目标。

以下示例会生成包含 maximize_conversions 的字段掩码。不过，Google Ads API 不允许这种行为，以防止意外清除字段，并会生成 FieldMaskError.FIELD_HAS_SUBFIELDS 错误。

警告： 以下代码会产生错误。

// 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 the FieldMasks' allSetFieldsOf utility to
// derive the update mask. The field mask will include 'maximize_conversions`,
// which will produce 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 will result in a
// FieldMaskError.FIELD_HAS_SUBFIELDS error because empty MESSAGE fields cannot
// be included in a field mask.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

以下示例演示了如何正确更新广告系列以使用 MaximizeConversions 出价策略，而无需设置其任何子字段。

成功： 以下代码成功更新了广告系列出价策略。

// 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 existing campaign and adds all of the mutable
// fields (only one in this case) on the MaximizeConversions bidding strategy to
// the field mask. Because this field is included in the field mask but
// excluded from the campaign object, the Google Ads API will set the campaign's
// bidding strategy to a MaximizeConversions object without any of its subfields
// set.
FieldMask fieldMask = FieldMasks.allSetFieldsOf(campaign)
    .toBuilder()
    // Only include 'maximize_conversions.target_cpa_micros' in the field mask
    // as it is the only mutable subfield on MaximizeConversions when used as a
    // standard bidding strategy.
    //
    // Learn more about standard and portfolio bidding strategies here:
    // https://developers.google.com/google-ads/api/docs/campaigns/bidding/assign-strategies
    .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();

清除字段

某些字段可以明确清除。与上述示例类似，您必须将这些字段明确添加到字段掩码中。例如，假设您有一个广告系列使用的是 MaximizeConversions 出价策略，并且 target_cpa_micros 字段的值设为大于 0 的值。

以下代码会运行；不过，系统不会将 maximize_conversions.target_cpa_micros 添加到字段掩码，因此不会对 target_cpa_micros 字段进行任何更改：

警告 ：此代码不会产生错误，但不会清除 MaximizeConversions 出价策略的 target_cpa_micros。

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

// Constructs an operation, using the FieldMasks' allSetFieldsOf utility to
// derive the update mask. However, the field mask will NOT include
// 'maximize_conversions.target_cpa_micros'.
CampaignOperation operation =
    CampaignOperation.newBuilder()
        .setUpdate(campaign)
        .setUpdateMask(FieldMasks.allSetFieldsOf(campaign))
        .build();

// Sends the operation in a mutate request that will succeed but will NOT update
// the 'target_cpa_micros' field because
// 'maximize_conversions.target_cpa_micros' was not included in the field mask.
MutateCampaignsResponse response =
    campaignServiceClient.mutateCampaigns(
        customerId.toString(), Collections.singletonList(operation));

以下示例演示了如何正确清除 MaximizeConversions 出价策略的 target_cpa_micros 字段。

成功： 以下代码确实会清除 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 existing campaign and adds the
// 'maximize_conversions.target_cpa_micros' field to the field mask, which will
// clear 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();

请注意，对于在 Google Ads API protocol buffers 中定义为 optional 的字段，上述“不正确”示例确实会按预期运行。但是，由于 target_cpa_micros 不是 optional 字段，因此“不正确”示例不会更新出价策略以清除 target_cpa 字段。

要点 ：如果您打算清除某个字段，实现此目标的最安全方式是将该字段明确添加到字段掩码中。