当我使用带有CloudBackendMessaging.TOPIC_ID_BROADCAST的subscribeToCloudMessage()函数作为在CloudBackendFragment.java中完成的topicId时,一切正常但是当我给这个函数我自己的字符串时,我收到以下消息:
错误:
m.google.api.client.googleapis.json.GoogleJsonResponseException: 400 Bad Request "code": 400, "errors": [ { "domain": "global", "message": "SubscriptionIDs: String properties must be 500 characters or less. Instead, use com.google.appengine.api.datastore.Text, which can store strings of any length.", "reason": "badRequest" } ], "message": "SubscriptionIDs: String properties must be 500 characters or less. Instead, use com.google.appengine.api.datastore.Text, which can store strings of any length." at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:111) at com.google.api.client.googleapis.services.json.AbstractGoogleJsonClientRequest.newExceptionOnError(AbstractGoogleJsonClientRequest.java:38) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest$1.interceptResponse(AbstractGoogleClientRequest.java:312) at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:1042) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:410) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:343) at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:460) at com.google.cloud.backend.core.CloudBackend.list(CloudBackend.java:314) at com.google.cloud.backend.core.CloudBackendAsync.access$8(CloudBackendAsync.java:1) at com.google.cloud.backend.core.CloudBackendAsync$9.callBackend(CloudBackendAsync.java:270) at com.google.cloud.backend.core.CloudBackendAsync$9.callBackend(CloudBackendAsync.java:1) at com.google.cloud.backend.core.CloudBackendAsync$BackendCaller.run(CloudBackendAsync.java:402)
Juniper.. 5
此错误消息表示该属性SubscriptionIDs
(您可以_DeviceSubscription
在数据存储区中的Kind 下找到它)超过500个Unicode字符限制.阅读文档以供参考.
来自文档:
对于文本字符串和未编码的二进制数据(字节字符串),数据存储区支持两种值类型:
短字符串(最多500个Unicode字符或字节)被编入索引,可用于查询过滤条件和排序顺序.
Longstrings(最多1兆字节)未编入索引,不能用于查询过滤器和排序顺序.
发生这种情况的原因是MBS试图将所有订阅写入一个属性.
因此,要解决这个问题,我们需要使用Text
替代String
型MBS后端的源代码的SubscriptionIDs
属性.为此,您需要在DeviceSubscription.java
课堂上进行以下更改:
要设置Text
属性,请替换以下代码行:
deviceSubscription.setProperty(PROPERTY_SUBSCRIPTION_IDS, this.gson.toJson(subscriptions));
用这一行:
deviceSubscription.setProperty(PROPERTY_SUBSCRIPTION_IDS, new Text(this.gson.toJson(subscriptions)));
要从Text
数据存储区获取属性:
替换此行:
String subscriptionString = (String) deviceSubscription.getProperty(PROPERTY_SUBSCRIPTION_IDS);
有了这个:
Text text = (Text) deviceSubscription.getProperty(PROPERTY_SUBSCRIPTION_IDS); String subscriptionString = text.getValue();
替换此行:
String ids = (String) deviceSubscription.getProperty(PROPERTY_SUBSCRIPTION_IDS);
有了这个:
Text text = (Text) deviceSubscription.getProperty(PROPERTY_SUBSCRIPTION_IDS); String ids = text.getValue();
替换此行:
String[] ids = new Gson().fromJson((String) entity.getProperty(PROPERTY_SUBSCRIPTION_IDS), String[].class);
有了这个:
Text text = (Text) entity.getProperty(PROPERTY_SUBSCRIPTION_IDS); String[] ids = new Gson().fromJson(text.getValue(), String[].class);
似乎是有效的解决方案.到目前为止,我还没有注意到对我项目的负面影响.
注:由于文档说Text
是没有索引,不能在查询过滤器使用和排序顺序.因此,如果SubscriptionIDs
需要对属性进行索引,则此限制可能会导致另一个问题.