I'll explain the situation. I followed these two great tuto:
http://rominirani.com/2014/01/10/google-cloud-endpoints-tutorial-part-1/
https://cloud.google.com/developers/articles/how-to-build-mobile-app-with-app-engine-backend-tutorial
However, they explain how create API for Google Cloud Endpoint, with entities independent from each other. So the API class looks like this:
package com.example.mobileassistant;
import javax.persistence.Entity;
import javax.persistence.Id;
/**
* Offer entity.
*/
#Entity
public class Offer {
#Id
private String offerId;
private String title;
private String description;
private String imageUrl;
.... (With Getter and Setter)
}
My question is: How to create a class with a parent entity of another? Like the entitie Wheel, with Parent Car. I can not create a relationship with its parent entity (With the annotation)!
I tried this but it did not seem to work (Foreign Key):
package com.example.mobileassistant;
import javax.jdo.annotations.ForeignKey;
import javax.persistence.Entity;
import javax.persistence.Id;
/**
* Offer entity.
*/
#Entity
public class Wheel {
#Id
private String Id;
#ForeignKey
private String parent_id;
private String title;
private String description;
.... (With Getter and Setter)
}
Actually, I have given up JDO because it don't really support parent entity, like I can read here: http://www.igorkromin.net/index.php/2013/03/14/jdo-youre-dumped-app-engine-and-bi-directional-relationships/
So I'm using now Objectify with Google Cloud Endpoint (For my Android App) and It works so perfect, especially with parent/child relationship !! You can read example here: http://blog.xebia.fr/2014/06/23/google-app-engine-cloud-endpoint-creer-notre-api-v2-et-lutiliser-avec-angularjs/
Why would it when you put it there?
See this page
http://www.datanucleus.org/products/accessplatform/jpa/annotations.html#ForeignKey
which explains clear enough that it is part of the JoinColumn, JoinTable, CollectionTable, SecondaryTable annotations.
Related
Does Spring Data REST support adding custom behavior to single repositories with Spring Data MongoDB and exposing it as a rest resource?
For example, here is the pojo:
#Document
#Data
#EqualsAndHashCode
public class Poet {
#Id
private String id;
private String title;
private String author;
private String content;
}
And Here is the repository:
#CrossOrigin
#RepositoryRestResource
public interface PoetRepository extends MongoRepository<Poet, String>, MyPoetRepository {
}
Can I find all the distinct title attribute in the document poet by extending a custom interface? By the way, how to implement the custom interface?
I'm new to Datastore and now I'm developing Gae application with Datastore and Objectify. Entity class has the form
#Entity
public class MyClass1 {
public Key<MyClass2> field1;
#Id Long id;
and so on
}
MyClass2 has the form
#Entity
public class MyClass2 {
....
#Id public Long id;
#Index public String field2;
....
}
I have entity of MyClass1. How can I get the value of field2 ?
If I use DatastoreService1.get(myclass1.field1) I get
method get(Key) in the DatstoreService is not applicable for arguments (Key<MyClass2>)
Please help me
Your error doesn't really relate to the question, so I assume you want to get the value of field1, not field2.
The error is because the DatastoreService get() method expects a com.google.appengine.api.datastore.Key, but you are passing it a com.googlecode.objectifyKey<T>, which is an Objectify key - they're not the same thing. Here are the docs.
I would recommend using a Ref<MyClass2> as you can then just do something like:
MyClass2 myClass2 = myClass1.field1.get();
(using your code example).
I have a datastore kind in which the ID field is String
ofy().load().type( Scores.class ).id( playerName ).now();
This fetches null. I have confirmed the entity with the given playername exists.
This does not happen to another Kind whose ID is long.
Code for Scores class
import com.googlecode.objectify.Key;
import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Id;
import com.googlecode.objectify.annotation.Parent;
#Entity
public class Scores
{
#Parent
public Key<RankerRoot> parentKey;
#Id
public String playerName;
public int value;
}
You need to be sure you are giving Objectify enough information to construct the entity's Key. So, if the entity has an ancestor, the ID/Name alone will be insufficient.
If your entity has an ancestor, you can construct the Key and then load the entity by Key, like this:
Key<Scores> scoreKey = Key.create(parentKey, Scores.class, playerName);
ofy().load().key(scoreKey).now();
I am using objectify 3.1 on appengine and attempting to do a ancestor query. I want to fetch all the children of an object that are of a certain kind. Below is my code:
#Cached
#Entity
public class Car {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String make;
private String model;
}
#Cached
#Entity
public class Tire {
#Id
public String keyName;
#Parent Key<Car> car;
private String brand;
private String size;
}
My query is this code:
List<Tire> list= ofy.query(Tire.class).ancestor(new Key<Car(Car.class,carID))).list();
When I create the tire objects I use this code to set the relationship:
newTire.setCar(new Key<Car>(Car.class,Car.getID()));
I know the Parent relationship is there because I can query for it in the datastore admin and it shows the parent in the decoded entity key:
Decoded entity key: Car: id=135172 > Tire: name=myCarUniqueID
This query always returns 0 results, and it seems like I have followed all the best practices on the objectify website. Any help would be appreciated!
Your code looks ok, so the only thing that might be wrong is a non-existing carID.
The Objectify javadoc listed on the site is actually for trunk version which is a forthcoming Objectify 4. What you need to look at is Objectify 3.1 javadoc: this version has fetch() on the query.
Also, #GeneratedValue is not an Objectify annotation.
first post here, hoping someone could perhaps shed some light on an issue I've been trying to juggle...
As a part of a school project we're attempting to build a interface to display points on a map and paths on a map.
For our first sprint I managed to work out storing/retrieving items using Objectify - it went great!
Now we're trying to extend the functionality for our next spring. Having problems now trying to store an object of type MapPath (note MapPath and MapData, our two data types, both extend class Data). Brief code snippets as follows :
#Entity
public class Data extends JavaScriptObject
{
#Id
Long id;
private String name;
private String dataSet;
...getters and setters
}
#Subclass
public class MapData extends Data implements Serializable{
{
private String name;
private String address;
private String dataSet;
#Embedded
private Coordinate location;
....constructors, getters/setters
}
#Subclass
public class PathData extends Data implements Serializable{
private String name;
private String address;
private String dataSet;
#Embedded
private Coordinate[] path;
...etc
}
Now hopefully I haven't lost you yet. I have a DataService class that basically handles all transactions. I have the following unit test :
#Test
public void storeOnePath(){
PathData pd = new PathData();
pd.setName("hi");
DataService.storeSingleton(pd);
Data d = DataService.getSingleton("hi");
assertEquals(pd,d);
}
The implementation of getSingleton is as follows :
public static void storeSingleton(Data d){
Objectify obj = ObjectifyService.begin();
obj.put(d);
}
JUnit complains:
java.lang.ExceptionInInitializerError
at com.teamrawket.tests.DataTest.storeOnePath(DataTest.java:59)
...<taken out>
Caused by: java.lang.IllegalStateException: Attempting to create multiple associations on class com.teamrawket.server.MapData for name
at com.googlecode.objectify.impl.Transmog$Visitor.addRootSetter(Transmog.java:298)
at com.googlecode.objectify.impl.Transmog$Visitor.visitField(Transmog.java:231)
at com.googlecode.objectify.impl.Transmog$Visitor.visitClass(Transmog.java:134)
at com.googlecode.objectify.impl.Transmog.<init>(Transmog.java:319)
at com.googlecode.objectify.impl.ConcreteEntityMetadata.<init>(ConcreteEntityMetadata.java:75)
at com.googlecode.objectify.impl.Registrar.registerPolymorphicHierarchy(Registrar.java:128)
at com.googlecode.objectify.impl.Registrar.register(Registrar.java:62)
at com.googlecode.objectify.ObjectifyFactory.register(ObjectifyFactory.java:209)
at com.googlecode.objectify.ObjectifyService.register(ObjectifyService.java:38)
at com.teamrawket.server.DataService.<clinit>(DataService.java:20)
... 27 more
What exactly does "attempting to create multiple associations on class ... for name" imply?
Sorry for the long post and any formatting issues that may arise.
You have repeated field names in your subclasses. You should not declare 'name' and 'dataSet' in both superclasses and subclasses; remove these fields from MapData and PathData and you should be fine.
com.teamrawket.server.MapData refers to the fullPath name for your MapData file. The name at the end refers to the field String name in your MapData class. This whole exception tries to tell you that it already contains a reference for that specific fullPath.
I would say there is another object with the same fullPath already registered. It would be helpful to know where line 59 is exactly as that is where the error occured.