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From Carlos Pita <carlosjosep...@gmail.com>
Subject Re: Lazy loading differences between ibatis 2 and 3
Date Wed, 16 Dec 2009 17:16:15 GMT
Hi Christian,

I understand your point but I don't get its relation to my question at
all. Continuing your example, I would ask why employee.getName() will
prematurely load the boss. A priori, I would expect the proxy to be
smarter and only trigger the loading of boss if getBoss() was
effectively called.

Regards
--
Bardamu

On Wed, Dec 16, 2009 at 3:09 PM, Poitras Christian
<Christian.Poitras@ircm.qc.ca> wrote:
> Hi,
>
> The major problem that was present in iBATIS 2 was that lazy loaded class where not always
of the right type.
> For exemple, if I have multiple subclasses of a class.
> Person
> Employee inherits Person
> Director inherits Employee
>
> If I have an object Employee with a method getBoss() that returns an Employee (lazy loaded),
I expect that sometimes it will be a director.
> In iBATIS 2, testing (employee.getBoss() instanceof Director) will always be false. This
problem is due to the fact that iBATIS does not know the real class of the boss property and
creates a Proxy of Employee.
> In iBATIS 3, testing (employee.getBoss() instanceof Director) will be true if the employee's
boss is a Director. To know the real type, the statement must be executed.
>
> Christian
>
>
> -----Original Message-----
> From: Carlos Pita [mailto:carlosjosepita@gmail.com]
> Sent: Wednesday, December 16, 2009 11:45 AM
> To: user-java@ibatis.apache.org
> Subject: Lazy loading differences between ibatis 2 and 3
>
> Hi all,
>
> I've the following sqlmap for ibatis 2. Suppose ibatis has its lazy-loading feature enabled
and I obtain a user U by means of findUserById. Then I call U.getEmail() and findMemberById
is not executed. That's fine, one wouldn't expect the associated member to be loaded until
there is a real need for it. Of course, if then I call
> U.getMember().getDescription() findMemberById does execute its select, in due time. That
said, for ibatis 3 the same example executes findMemberById as soon as U.getEmail() is invoked,
loading the member before time. That's not surprising if one inspects the code of ResultObjectProxy
(relevant parts copied below). Is this intended to work the way it does or is it a bug?
>
> <sqlMap namespace="User">
>
>        <resultMap id="userMap" class="User">
>        <result property="email" column="email"/>
>        <result property="member" column="member_id" select="findMemberById"/>
>        </resultMap>
>
>        <resultMap id="memberMap" class="Member">
>        <result property="description" column="description"/>
>        </resultMap>
>
>        <select id="findUserById" resultMap="userMap">
>                select * from qpoint_user where id = #id#
>        </select>
>
>        <select id="findMemberById" resultMap="memberMap">
>                select * from cpp_member where member_id = #id#
>        </select>
>
> </sqlMap>
>
>
> public class ResultObjectProxy {
>
>   public Object invoke(Object o, Method method, Object[] args) throws Throwable {
>      try {
>        if (!Object.class.equals(method.getDeclaringClass()) &&
> PropertyNamer.isGetter(method.getName())) {
>            lazyLoader.loadAll(); <-- this loads all asociations for every getter
invoked on this proxy
>        }
>        return method.invoke(target, args);
>      } catch (Throwable t) {
>        throw ExceptionUtil.unwrapThrowable(t);
>      }
>    }
> }
>
> Regards
> --
> Bardamu
>
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