Null-References for sub selects with lazy loading
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Key: IBATIS-596
URL: https://issues.apache.org/jira/browse/IBATIS-596
Project: iBatis for Java
Issue Type: Improvement
Components: SQL Maps
Affects Versions: 2.3.4
Reporter: Stefan Gmeiner
We are using the iBatis enhanced (cglib) proxy for lazy loading our sub-select
bean references.
Unfortunately if a reference is null iBatis creates a proxy with
null content. This makes using lazy loading less transparent to clients as they
are required
to execute further checks to see if the returned object is null.
Hence we are suggesting a simple solution which is attached as a patch:
A proxy for a lazy loaded object is now only created if the foreign key is
non-null.
When using the curly braces syntax (parameter map) a postfix '?' is required to
activate
the new lazy loading otherwise the existing strategy is used. This allows for
the possibility
of subselects requiring a null value as foreign key.
Example:
<result property="jobs" column="job_pk" select="selectJob"/>
This will return null if job_pk is null and a proxy for the job is job_pk is
not null.
<result property="jobs" column="{transportIdentifier=job_pk}"
select="selectJob"/>
This will always return a proxy object irrespective of the job_pk value.
<result property="jobs" column="{transportIdentifier=job_pk?}"
select="selectJob"/>
This will return null if job_pk is null and a proxy for the job is job_pk is
not null.
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