hello.
I have a problem when trying to update an object that has already been
saved in the dataStore....
An Employee and Contactnfo. One employee has a contactInfo...
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
@PersistenceCapable(detachable = "true")
public class Employee implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
@Persistent
private ContactInfo contactInfo = null;
public ContactInfo getContactInfo() {
return contactInfo;
}
public void setContactInfo(ContactInfo contactInfo) {
this.contactInfo = contactInfo;
}
public Key getKey() {
return key;
}
}
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
@PersistenceCapable(detachable = "true")
public class ContactInfo implements Serializable {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key key;
@Persistent
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Key getKey() {
return key;
}
public void setKey(Key key) {
this.key = key;
}
}
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////////////
my servlet:
public class GreetingServiceImpl extends RemoteServiceServlet
implements GreetingService {
private static final PersistenceManagerFactory pmfInstance =
JDOHelper.getPersistenceManagerFactory("transactions-optional");
public String greetServer(String input) {
String result = "";
//step1 create and save an employee in the datastore.
Key key = storeEmployeeInDatastore();
//step2 retrieve the employee from the datastore and detach it
Employee detachedEmployee = getDetachedEmployee(key);
//step3 modify the detached employee
ContactInfo contactInfo2 = new ContactInfo();
detachedEmployee.setContactInfo(contactInfo2);
//step4 save the modified employee...
updateEmployeeInDataStore(detachedEmployee);
return result;
}
/**
* @return the key of the employee that has been stored
*/
private Key storeEmployeeInDatastore() {
Employee employee = new Employee();
ContactInfo contactInfo = new ContactInfo();
employee.setContactInfo(contactInfo);
//creates a new manager.
PersistenceManager manager1 = pmfInstance.getPersistenceManager();
Key key = null;
try {
manager1.makePersistent(employee);
key = employee.getKey();
}
catch ( Exception e ) {
e.printStackTrace();
}
finally {
//equivalent to manager1.close()
manager1.close();
}
return key;
}
private Employee getDetachedEmployee(Key key) {
PersistenceManager manager2 = pmfInstance.getPersistenceManager();
Employee attached = manager2.getObjectById(Employee.class, key);
Employee detachedEmployee = manager2.detachCopy(attached);
manager2.close();
return detachedEmployee;
}
private void updateEmployeeInDataStore(Employee detachedEmployee) {
PersistenceManager manager3 = pmfInstance.getPersistenceManager();
try {
Employee bidon = manager3.makePersistent(detachedEmployee);
System.out.println("");
}
catch ( Exception e ) {
e.printStackTrace();
}
finally {
manager3.close();
}
}
}
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
HERE IS THE ERROR I GET
org.datanucleus.store.appengine.DatastoreRelationFieldManager
$ChildWithoutParentException: Detected attempt to establish
Employee(4) as the parent of ContactInfo(6) but the entity identified
by ContactInfo(6) has already been persisted without a parent. A
parent cannot be established or changed once an object has been
persisted.
at
org.datanucleus.jdo.NucleusJDOHelper.getJDOExceptionForNucleusException(NucleusJDOHelper.java:
354)
at
org.datanucleus.jdo.JDOPersistenceManager.close(JDOPersistenceManager.java:
281)
at
com.gae.server.GreetingServiceImpl.updateEmployeeInDataStore(GreetingServiceImpl.java:
85)
at
com.gae.server.GreetingServiceImpl.greetServer(GreetingServiceImpl.java:
33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:
39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:
25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:
100)
at
com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:
562)
////////////////////////////////////////////////////////////////////////////////////////
Can Anyone explain me what's wrong... and can anyone explain to me how
I can do the 4 steps!
//step1 create and save an employee in the datastore.
//step2 retrieve the employee from the datastore and detach it
//step3 modify the detached employee
//step4 save the modified employee...
Thank you in advance.
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