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Re: [Springframework-developer] Re: Final methods in SqlQuery
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From: Michael Y. <sp...@on...> - 2004-01-09 01:09:58
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Juergen,
Since I have my own JdbcTemplate, I have to overwrite the setDataSource met=
hod
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 m=
ain framework: It is not meant to be a base class for customized DAO base c=
lasses but rather a convenience base class for concrete DAOs. In all other =
cases, use straightforward DAO implementations that expose their dependenci=
es, or create your own base class that accepts a DataSource and/or JdbcTemp=
late instance. We should probably clarify this in the Javadocs.
> =20
> Why exactly do you want to override JdbcDaoSupport's methods? The only th=
ing that I can imagine is using your own subclass of JdbcTemplate: You coul=
d achieve this easily by setting up your JdbcTemplate instance in the appli=
cation context and passing it to JdbcDaoSupport's "jdbcTemplate" property -=
actually, pre-configured JdbcTemplate instances is exactly what that prope=
rty is for.
> =20
> JdbcDaoSupport is really a *very simple* convenience base class for stand=
ard JDBC-based DAOs, so I don't consider it inappropriate to create your ow=
n class here... (your own class can even derive from any other base class t=
hen). And if you don't set a pre-configured JdbcTemplate anyway, you just n=
eed setDataSource and getJdbcTemplate methods.For example, with a custom su=
bclass 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 SqlMapDaoSupp=
ort: They are all supposed to serve as convenience DAO base classes for *ty=
pical* scenarios, to be replaced by custom base classes or no base classes =
at all in case of special requirements.
> =20
> Juergen
> =20
>=20
> ________________________________
>=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
>=20
>=20
>=20
> Rod,
>=20
> 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.
>=20
> My issue was the following:
>=20
> 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.
>=20
> This is why I have to overwrite afterPropertiesSet() in my subclass
> of JdbcTemplate.
>=20
> 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.
>=20
> I'm not really complaining, but just hope for improvements in Spring.
>=20
> Thanks! /Michael.
>=20
> On Friday, Jan-02-2004 10:12 AM (PST) rod...@in... (Rod Jo=
hnson) wrote:
>=20
> > I don't object to making more methods non-final, as people do ask for t=
his.
> >
> > 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=FC=
rgen
> > h=F6ller [werk3AT]) wrote:
> >
> > > This sounds plausible to me. I'll look into turning appropriate metho=
ds
> > 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 fo=
r
> > 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 ge=
neral
> > extension hook. I've already applied the same principle in the bean fac=
tory
> > 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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