Java 如何用Guice注入googleappengine数据存储？

我正试图通过Guice将Google App Engine的数据存储注入我的服务：

public class FooServiceImpl implements FooService {

    private final DatastoreService datastoreService;

    @Inject
    public FooServiceImpl (DatastoreService datastoreService) {
        this.datastoreService = datastoreService;
    }
}

但当我尝试运行它时，会出现以下错误：

未绑定com.google.appengine.api.datastore.DatastoreService的实现

将方法添加到模块：

@Provides
DatastoreService provideDatastoreService(){
    return DatastoreServiceFactory.getDatastoreService();
}