CODEWITHSUNDEEP
google-app-enginegoogle-cloud-datastorejdo
Kerem Pekçabuk
Kerem Pekçabuk

Reputation: 71

How to instert child entities in JDO (Google App Engine)?

How do i add a record to a child entity in the example below ? For example i have a Employee Record which is name is "Sam". how do i add 2 street adress for sam ?

Guess i have a

The Parent entity is Employee

import java.util.List;

// ...
@Persistent(mappedBy = "employee")
private List<ContactInfo> contactInfoSets;

The Child key is Adress

import com.google.appengine.api.datastore.Key;
// ... imports ...

@PersistenceCapable
public class ContactInfo {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;

    @Persistent
    private String streetAddress;

    // ...
}

Upvotes: 2

Views: 1230

Answers (2)

Arun
Arun

Reputation: 2840

Inserting and retrieving Child Entries can be done in the following way:

Parent class Person

@PersistenceCapable(identityType=IdentityType.APPLICATION,detachable = "true")
public class Person {
@PrimaryKey
@Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY)
Long id ;
@Persistent
String strName;
@Persistent
String phnNumber;
@Persistent
String strEmail;
@Nullable
@Persistent(defaultFetchGroup="true")
@Element(dependent="true")
//When adding Person Contacts would be added as it is dependent. Also while retrieving
// add defaultFetchGroup = true to retrieve child elements along with parent object.
List<Contacts> lstContacts;

// getter and setter methods

}

Dependent Child Class : Contacts

@PersistenceCapable(identityType=IdentityType.APPLICATION,detachable = "true")
public class Contacts 
{
@PrimaryKey  
@Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY)
Key id;
@Persistent
String email;
@Persistent
String phNumber;
   //getter and setter methods
  }

Upvotes: 0

hleinone
hleinone

Reputation: 4480

It just works:

Employee sam = new Employee("Sam");
List<Address> addresses = new ArrayList<Address>();
addresses.add(new Address("Foo St. 1"));
addresses.add(new Address("Bar Bvd. 3"));
sam.setAddresses(addresses);
persistenceManager.makePersistent(sam);

Employee being:

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
public class Employee {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;
    private List<Address> addresses;
    ...
}

Address being:

@PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true")
public class Address {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;
    ...
}

Use @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable = "true") as the class level annotation. Usually you don't need to annotate any other fields but the key, so the @Persistent(mappedBy = "employee") on the List is unnecessary.

Btw. I suggest using parametrized collections.

Upvotes: 2

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