Datastore is a application based on BigTable. It’s a No-Sql data base. Datastore runs on Google Cloud. It’s based on key-value, column oriented. Datastore is managed by google so you get the scability, stability… Also, you need to pay for these abilities.
BigTable white paper: [http://research.google.com/archive/bigtable.html]
Each Cloud Datastore entity is of a particular kind, which categorizes the entity for the purpose of queries: for instance, a human resources application might represent each employee at a company with an entity of kind Employee.
Data objects in Cloud Datastore are known as entities. An entity has one or more named properties, each of which can have one or more values.
Entities of the same kind do not need to have the same properties, and an entity’s values for a given property do not all need to be of the same data type.
udacity show a way to create entity with annotation:
import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Id;
/* Recipe entities */
@Entity
public class Recipe {
@Id Long recipeId;
String name;
Boolean vegetarian;
Integer servings;
String ingredients;
String instructions;
public Recipe() {
};
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
// rest of setters and getters
}
see also: [https://classroom.udacity.com/courses/ud859/lessons/1231898607/concepts/14568985500923]
google doc give a another, which uses constructing methods of Entity class directly.
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
Entity employee = new Entity("Employee", "asalieri");
employee.setProperty("firstName", "Antonio");
employee.setProperty("lastName", "Salieri");
employee.setProperty("hireDate", new Date());
employee.setProperty("attendedHrTraining", true);
datastore.put(employee);
see also: [https://cloud.google.com/appengine/docs/java/datastore/entities]
API: [https://cloud.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/Entity]
Each property has a name and one or more values. And property is asscociated with entity.
Google give you a lot properties to use. Really A lot!
check out here: [https://cloud.google.com/appengine/docs/java/datastore/entities#Java_Properties_and_value_types]
It’s depends on how to define your entity.
With Entity()
As far as your class object is a entity. You can do this simply following the Employee example.
With Annotation
In this case, you Class is not a Entity. So, you can use fellowing code to register your class and put to datastore.
import com.google.devrel.training.conference.domain.Profile;
import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyFactory;
import com.googlecode.objectify.ObjectifyService;
/**
* Custom Objectify Service that this application should use.
*/
public class OfyService {
/**
* This static block ensure the entity registration.
*/
static {
factory().register(Profile.class);
}
/**
* Use this static method for getting the Objectify service object in order to make sure the
* above static block is executed before using Objectify.
* @return Objectify service object.
*/
public static Objectify ofy() {
return ObjectifyService.ofy();
}
/**
* Use this static method for getting the Objectify service factory.
* @return ObjectifyFactory.
*/
public static ObjectifyFactory factory() {
return ObjectifyService.factory();
}
}
to get back the profile.
@ApiMethod(name = "getProfile", path = "profile", httpMethod = HttpMethod.GET)
public Profile getProfile(final User user) throws UnauthorizedException {
if (user == null) {
throw new UnauthorizedException("Authorization required");
}
// TODO
// load the Profile Entity
String userId = user.getUserId(); // TODO
Key key = Key.create(Profile.class, userId); // TODO
Profile profile = (Profile) ofy().load().key(key).now(); // TODO load the Profile entity
return profile;
}