6:48 p.m.
Custom types with auto-generated keys
-------------------------------------
Key: HHH-3657
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3657
Project: Hibernate Core
Issue Type: New Feature
Components: core
Affects Versions: 3.3.1
Reporter: David Nadaski
Attachments: IdentifierGeneratorFactory.java
Hibernate should provide for custom types to be usable with auto-generated ids.
Attached is a patch, untested but supposedly working (it works for our site flawlessly),
and here's a short description, copied from 2 email that I've sent to the dev list
and forum:
So in response to my previous mail, I've applied a short fix for
IdentifierGeneratorFactory to enable custom types to be used for auto-generated keys.
Here's IdentifierGeneratorFactory's modified public static Serializable get(....)
method, which was extended based on the 3.3.1.GA release:
public static Serializable get(ResultSet rs, Type type) throws SQLException,
IdentifierGenerationException {
Class clazz = type.getReturnedClass();
if ( clazz == Long.class ) {
return new Long( rs.getLong( 1 ) );
}
else if ( clazz == Integer.class ) {
return new Integer( rs.getInt( 1 ) );
}
else if ( clazz == Short.class ) {
return new Short( rs.getShort( 1 ) );
}
else if ( clazz == String.class ) {
return rs.getString( 1 );
}
else {
// try to instantiate the custom type through reflection
try {
Constructor<?>[] constructors =
type.getReturnedClass().getConstructors();
for (Constructor<?> constructor : constructors)
{
Class<?>[] parameterTypes =
constructor.getParameterTypes();
if (parameterTypes.length == 1)
if (Long.class.equals(parameterTypes[0]))
return (Serializable) constructor.newInstance(rs.getLong(1));
else if (Integer.class.equals(parameterTypes[0]))
return (Serializable)
constructor.newInstance(rs.getInt(1));
else if (Short.class.equals(parameterTypes[0]))
return (Serializable)
constructor.newInstance(rs.getShort(1));
else if (String.class.equals(parameterTypes[0]))
return (Serializable)
constructor.newInstance(rs.getString(1));
}
} catch (Throwable t) {
throw new IdentifierGenerationException( "Error instantiating custom
type: " + type + " with value class: " + type.getReturnedClass(), t );
}
throw new IdentifierGenerationException( "Supplied custom type
doesn't have a 1-argument constructor which could take either long, integer, short or
string: " + type.getReturnedClass().getName() );
}
}
So this would allow you to use any class for an auto-generated ID, for example:
public class UniqueInteger implements Serializable {
private Integer internal;
public UniqueInteger()
{
}
public UniqueInteger(Integer internal)
{
this.internal = internal;
}
}
The only requirement is that it should have a 1-argument constructor that can take either
long, integer, short or string.
Which I think makes sense.
Please submit your feedback and thoughts on this!
--Dávid
--------------------------------------------------------------------------------
From: Nádaski Dávid [mailto:david@aquilanet.hu]
Sent: Wednesday, December 10, 2008 7:23 AM
To: 'hibernate-dev(a)lists.jboss.org'
Subject: Using custom types for auto-generated id columns
Hi,
I was trying to use a custom type for which there was a valid Type implementation, and
have run into the following error:
28240 [http-8080-1] ERROR org.hibernate.event.def.AbstractFlushingEventListener - Could
not synchronize database state with session
org.hibernate.id.IdentifierGenerationException: this id generator generates long, integer,
short or string
at
org.hibernate.id.IdentifierGeneratorFactory.get(IdentifierGeneratorFactory.java:116)
etc.
I'm using MySQL.
Looking at the source, it seems like Hibernate doesn't support anything other than a
"long, integer, short or string".
In the parameters of IdentifierGeneratorFactory.get(....), there's one called
"Type type". This gets mapped correctly to my custom, but since that's none
of those "primitive" types, I get the error - but since the Type information is
available, it could easily be used to map say a String using Type.nullSafeGet(ResultSet
rs, String[] names, SessionImplementor session, Object owner), since we have both the
ResultSet and the Type parameter available in IdentifierGeneratorFactory.get(ResultSet rs,
Type type). So then, the proper custom type could be returned if it indeed supports this
kind of mapping (which is by definition it's job).
So I propose a patch should be made to IdentifierGeneratorFactory that would enable the
use of custom types for identity-generated columns.
It's possible that I'm missing something, in that case please point out my error.
Upon request, I think I can supply the appropriate patch, although it seems easy to code.
Thanks,
David
That's the emails, you'll find the patch attached.
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