org.hibernate.dialect.function
Class DerbyConcatFunction
java.lang.Object
org.hibernate.dialect.function.DerbyConcatFunction
- SQLFunction
public class DerbyConcatFunction
extends java.lang.Object
A specialized concat() function definition in which:
- we translate to use the concat operator ('||')
- wrap dynamic parameters in CASTs to VARCHAR
This last spec is to deal with a limitation on DB2 and variants (e.g. Derby)
where dynamic parameters cannot be used in concatenation unless they are being
concatenated with at least one non-dynamic operand. And even then, the rules
are so convoluted as to what is allowed and when the CAST is needed and when
it is not that we just go ahead and do the CASTing.
render
public String render(List args,
SessionFactoryImplementor factory)
throws QueryException
Here's the meat.. The whole reason we have a separate impl for this for Derby is to re-define
this method. The logic here says that if not all the incoming args are dynamic parameters
(i.e. ?) then we simply use the Derby concat operator (||) on the unchanged
arg elements. However, if all the args are dynamic parameters, then we need to wrap the individual
arg elements in cast function calls, use the concantenation operator on the cast
returns, and then wrap that whole thing in a call to the Derby varchar function.
- render in interface SQLFunction