Single Persistent instance of a Object, Many non persistant. Same Identity on persist

Question

I have a persistent bean class with two Strings as member fields. (example
below)
I have many other classes that use it a part of they're member fields.
I need to have only one persistant version of it (One row, to many Rows in
different tables). But can have many non persistant versions. I can't
control the creation of the non persistant objects.
i.e.
On persist, How can I configuration JDO to detect that it's the same as an
object already in the database and use that instead?
example:
// Example class One
package foo;
public class One(){
public String var1;
public String var2;
public String getVar1(){
return this.var1;
public void setVar1(String var1Set){
this.var1 = var1Set
public String getVar2(){
return this.var2;
public void setVar2(String var2Set){
this.var2 = var2Set
/// one.jdo
<?xml version="1.0"?>
<jdo>
<package name="foo">
<class name="One"/>
</package>
</jdo>
///Example Scenario
One oneObject = new One();
oneObject.setVar1("Value1");
oneObject.setVar2("Value2");
pm.makePersistent(oneObject); // one row in database
/// Some time later, in a different thread, or since JVM shutdown and
restart
One oneObject = new One();
oneObject.setVar1("Value1");
oneObject.setVar2("Value2");
pm.makePersistent(oneObject); // one row in database, instead of two.

Answer 1

You cannot. You should either find the object by query or retrieve it
using application identity.
Graham Cruickshanks wrote:
I have a persistent bean class with two Strings as member fields. (example
below)
I have many other classes that use it a part of they're member fields.
I need to have only one persistant version of it (One row, to many Rows in
different tables). But can have many non persistant versions. I can't
control the creation of the non persistant objects.
i.e.
On persist, How can I configuration JDO to detect that it's the same as an
object already in the database and use that instead?
example:
// Example class One
package foo;
public class One(){
public String var1;
public String var2;
public String getVar1(){
return this.var1;
public void setVar1(String var1Set){
this.var1 = var1Set
public String getVar2(){
return this.var2;
public void setVar2(String var2Set){
this.var2 = var2Set
/// one.jdo
<?xml version="1.0"?>
<jdo>
<package name="foo">
<class name="One"/>
</package>
</jdo>
///Example Scenario
One oneObject = new One();
oneObject.setVar1("Value1");
oneObject.setVar2("Value2");
pm.makePersistent(oneObject); // one row in database
/// Some time later, in a different thread, or since JVM shutdown and
restart
One oneObject = new One();
oneObject.setVar1("Value1");
oneObject.setVar2("Value2");
pm.makePersistent(oneObject); // one row in database, instead of two.
Steve Kim
[email protected]
SolarMetric Inc.
http://www.solarmetric.com