如何修复错误：此服务需要项目 ID，但无法确定

我正在尝试从 AppEngine 将数据插入 Google 数据存储区，但收到错误：

java.lang.IllegalArgumentException: A project ID is required for this service but could not be determined from the builder or the environment.  Please set a project ID using the builder.
    at com.google.common.base.Preconditions.checkArgument(Preconditions.java:92)
    at com.google.cloud.ServiceOptions.<init>(ServiceOptions.java:324)
    at com.google.cloud.datastore.DatastoreOptions.<init>(DatastoreOptions.java:85)
    at com.google.cloud.datastore.DatastoreOptions.<init>(DatastoreOptions.java:32)
    at com.google.cloud.datastore.DatastoreOptions$Builder.build(DatastoreOptions.java:75)
    at com.google.cloud.datastore.DatastoreOptions.defaultInstance(DatastoreOptions.java:123)

这是我的代码：

Datastore datastore = DatastoreOptions.defaultInstance().service();     
             KeyFactory keyFactory = datastore.newKeyFactory().kind("keyKind"); 
             Key key = keyFactory.newKey("keyName"); 
             Entity entity = Entity.builder(key) 
                 .set("name", "John Doe") 
                 .set("age", 30) 
                 .set("access_time", DateTime.now()) 
                 .build(); 
             datastore.put(entity); 

我该如何修复这个错误？

就我而言，下一个代码正在运行：

    BigQuery bigquery = BigQueryOptions.newBuilder().setProjectId("XXXXX")
            .setCredentials(
                    ServiceAccountCredentials.fromStream(new FileInputStream("key.json"))
            ).build().getService();

我在构建器中设置了projectId。