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Re: [Springframework-developer] Re: Final methods in SqlQuery
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From: <jue...@we...> - 2004-01-09 06:04:35
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What I meant regarding JdbcDaoSupport's "jdbcTemplate" property is that =
could also set up your *JdbcTemplate* instance in the application =
context and pass it to your DAOs:
=20
<bean id=3D"myJdbcTemplate" class=3D"mypackage.MyJdbcTemplate">
<property name=3D"dataSource"><ref bean=3D"dataSource"/></property>
</bean>
=20
<bean id=3D"myDao" class=3D"mypackage.MyDao">
<property name=3D"jdbcTemplate"><ref =
bean=3D"myJdbcTemplate"/></property>
</bean>
=20
Your DAO class can then still derive from the standard JdbcDaoSupport, =
which offers exactly such a "jdbcTemplate" property. This is not only =
useful for custom JdbcTemplate subclasses but also for common =
JdbcTemplate settings like "exceptionTranslator" and "ignoreWarnings" =
that you just want to set up once and pass to all your DAOs.
=20
Juergen
=20
________________________________
Von: spr...@li... im Auftrag =
von Michael Young
Gesendet: Fr 09.01.2004 01:51
An: spr...@li...
Betreff: Re: [Springframework-developer] Re: Final methods in SqlQuery
Juergen,
Since I have my own JdbcTemplate, I have to overwrite the setDataSource =
method
in JdbcDaoSupport to create my own JdbcTemplate instance. If the
method is not final, I would be able to do so.
But like you said, I can easily create my own dao support class, which
is what I did as a workaround.
Thanks! --Pinghua
On Monday, Jan-05-2004 05:18 AM (PST) jue...@we... =
(j=FCrgen h=F6ller [werk3AT]) wrote:
> Michael,
>=20
> I can understand your concerns. But JdbcDaoSupport still belongs in =
the main framework: It is not meant to be a base class for customized =
DAO base classes but rather a convenience base class for concrete DAOs. =
In all other cases, use straightforward DAO implementations that expose =
their dependencies, or create your own base class that accepts a =
DataSource and/or JdbcTemplate instance. We should probably clarify this =
in the Javadocs.
>=20
> Why exactly do you want to override JdbcDaoSupport's methods? The only =
thing that I can imagine is using your own subclass of JdbcTemplate: You =
could achieve this easily by setting up your JdbcTemplate instance in =
the application context and passing it to JdbcDaoSupport's =
"jdbcTemplate" property - actually, pre-configured JdbcTemplate =
instances is exactly what that property is for.
>=20
> JdbcDaoSupport is really a *very simple* convenience base class for =
standard JDBC-based DAOs, so I don't consider it inappropriate to create =
your own class here... (your own class can even derive from any other =
base class then). And if you don't set a pre-configured JdbcTemplate =
anyway, you just need setDataSource and getJdbcTemplate methods.For =
example, with a custom subclass of JdbcTemplate:
>=20
> public abstract class MyJdbcDaoSupport {
>=20
> private JdbcTemplate jdbcTemplate;
>=20
> public final void setDataSource(DataSource dataSource) {
> this.jdbcTemplate =3D new MyJdbcTemplate(dataSource);
> }
>=20
> protected final getJdbcTemplate() {
> return jdbcTemplate;
> }
> }
>=20
> The same applies to HibernateDaoSupport, JdoDaoSupport, and =
SqlMapDaoSupport: They are all supposed to serve as convenience DAO base =
classes for *typical* scenarios, to be replaced by custom base classes =
or no base classes at all in case of special requirements.
>=20
> Juergen
>=20
>
> ________________________________
>
> Von: spr...@li... im Auftrag =
von Michael Young
> Gesendet: So 04.01.2004 19:54
> An: spr...@li...
> Betreff: Re: [Springframework-developer] Re: Final methods in SqlQuery
>
>
>
> Rod,
>
> Sorry about my confusion. Actually, what I had to work around
> JdbcTemplate is not the issue of final methods. There aren't
> any final methods in JdbcTemplate that I want to overwrite.
>
> My issue was the following:
>
> I want to overwrite afterPropertiesSet() in JdbcTemplate so that
> it won't call getExceptionTranslator() immediately when a
> datasource is being set. This is because my datasource is a wrapper
> for a bunch of datasources, so the real datasource is not known
> until it's actually used.
>
> This is why I have to overwrite afterPropertiesSet() in my subclass
> of JdbcTemplate.
>
> I was also using JdbcDaoSupport but its JavaBean set and get methods
> are all final, and this is the issue I was complaining. I have to
> create my own class rather than extending from JdbcDaoSupport. This
> is OK, but I really don't like the idea of methods being final
> when there are no such needs/benefits from it. JdbcDaoSupport is
> not a crucial class in the framework, but that doesn't mean that
> we shouldn't take care of it just like those important classes
> in the framework. It may be a trivial and unimportant class to
> you, but it was important to me because I was using it. And it
> may be important to others as well. If we are supposed to write
> our own rather than extending from it, then maybe it should not
> belong there. Maybe it should be in one of those sample apps.
>
> I'm not really complaining, but just hope for improvements in Spring.
>
> Thanks! /Michael.
>
> On Friday, Jan-02-2004 10:12 AM (PST) rod...@in... (Rod =
Johnson) wrote:
>
> > I don't object to making more methods non-final, as people do ask =
for this.
> >
> > However, in general I think there are better extension mechanisms =
than
> > overriding methods in Spring in many cases. I don't particularly =
like
> > overriding concrete methods as a means of extensibility.
> >
> > Why would you want to subclass JdbcTemplate?
> >
> > Why would you override JdbcDaoSupport's methods?
> >
> > I'm not being sarcastic, I'm just curious...
> >
> > Regards,
> > Rod
> >
> > ----- Original Message -----
> > From: "Michael Young" <sp...@on...>
> > To: <spr...@li...>
> > Sent: Friday, January 02, 2004 5:42 PM
> > Subject: Re: [Springframework-developer] Re: Final methods in =
SqlQuery
> >
> >
> > Juergen,
> >
> > Can you do the same for other classes as well? Classes such as
> > JdbcTemplate and JdbcDaoSupport. Someone also mentioned the
> > abstract wizard form controller as well. See messages previously
> > posted either here or in users.
> >
> > Thanks! /Michael.
> >
> > On Friday, Jan-02-2004 02:45 AM (PST) jue...@we... =
(j=FCrgen
> > h=F6ller [werk3AT]) wrote:
> >
> > > This sounds plausible to me. I'll look into turning appropriate =
methods
> > non-final today, if noone objects.
> > >
> > > The original rationale behind the final methods is to offer clear
> > extension points: Subclassers should know which methods are intended =
for
> > overriding and which are not, avoiding confusion. But I agree that =
this
> > doesn't work for cases that the framework developers didn't expect, =
so it's
> > probably better to not use final for methods where there is no clear =
general
> > extension hook. I've already applied the same principle in the bean =
factory
> > implementation hierarchy.
> > >
> > > Juergen
> > >
> > >
> > > ________________________________
> > >
> > > Von: spr...@li... im =
Auftrag von
> > David Heimann
> > > Gesendet: Fr 02.01.2004 02:24
> > > An: spr...@li...
> > > Betreff: [Springframework-developer] Re: Final methods in SqlQuery
> > >
> > >
> > >
> > > Ken and developers,
> > >
> > > I have a business rule in my system that all the data be
> > > stored in upper case in the database. This sugests the
> > > following design:
> > >
> > > 1)This is a business rule and so should be in the model
> > > layer rather than the presentation layer
> > >
> > > 2)The code to upper case the data should be centralized.
> > > Requiring each developer to upper case the data before
> > > calling the execute or update methods duplicates code and
> > > is error prone. (the PetClinic sample has around 12
> > > execute or update calls, each of which would need to be
> > > prefaced by upper casing code)
> > >
> > > 3)This suggests a design where I extend SqlUpdate and
> > > SqlQuery and override the SqlUpdate.update and
> > > SqlQuery.execute methods, for example
> > >
> > > public abstract SqlQueryUpper extends SqlQuery
> > > {
> > > public List execute(Object[] parameters, Map context)
> > > throws DataAccessException {
> > > //upper case string parameters
> > > for(int i =3D 0;i<parameters.length;i++)
> > > {
> > > Object p =3D parameters[i];
> > > if(p instanceof java.lang.String)
> > > {
> > > parameters[i] =3D p.toUpper();
> > > }
> > > }
> > > return super.execute(parameters, context);
> > > }
> > > }
> > >
> > > Of course, I could create my own method with a different
> > > name such as
> > > ...
> > > public List executeUpper(Object[] parameters, Map context)
> > > throws DataAccessException
> > > {
> > > (same as above)
> > > }
> > >
> > > But if I do that, then I
> > > 1)Still have the original SqlQuery.execute method out
> > > there which no one should use.
> > > 2)Do not have all the other signatures available such as
> > > SqlQuery.execute(int), SqlQuery.execute(String) etc because
> > > they all still go through the original execute method.
> > >
> > > Finally, my problem is an example of something not included
> > > or anticipated by the developers of the Spring Framework.
> > > There is no built in Spring 'auto-upper' option nor should
> > > there be. Putting final on methods stops me from adding it
> > > myself, making the framework unextendable in this area.
> > > IMHO final methods should be few and far between in an
> > > extensible framework and I do not think they are called for
> > > here.
> > >
> > > Sincerely,
> > >
> > > David Heimann
> > >
> > > >David,
> > > >
> > > > I don't understand why you think it would be nice to
> > > ***override*** it.
> > > > The execute method does all the IOC hard stuff for you.
> > > If you override
> > > > it, you have to do this yourself, adding unnecessary
> > > duplication. That's
> > > > why it's final. The same goes for SqlUpdate.update. In
> > > your example, why
> > > > not simply manipulate the parameters to your heart's
> > > content before
> > > > passing them to the execute method ?
> > > >
> > > > Ken
> > > >
> > > > Heimann, David X - San Mateo, CA wrote:
> > > >
> > > > > Developers,
> > > > >
> > > > > Could you change
> > > > >
> > > > > *public** final* List execute(*final* Object[]
> > > parameters, Map context)
> > > > > {
> > > > > ...
> > > > > }
> > > > >
> > > > > in org.springframework.jdbc.object.SqlQuery to not be
> > > final ? It
> > > > > would be nice to overload it, for example to change all
> > > parameters to
> > > > > upper case before executing. The similar update method
> > > in SqlUpdate
> > > > > is not final. Why be final at all ?
> > > > >
> > > > > David Heimann
> > > > >
> > >
> > >
> > > __________________________________
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