JPA says this is not supported. However it does not *explicitly* say it is not supported - it just "strongly implies" that it should be the column's "JDBC type" (the type of the column value in the ResultSet) in both the spec and its Javadoc. E.g.,
{code}
public @interface ColumnResult {
...
/**
* (Optional) The Java type to which the column type is to be mapped.
* If the <code>type</code> element is not specified, the default JDBC type
* mapping for the column will be used.
* @since Java Persistence 2.1
*/
Class type() default void.class;
}
{code}
However this is useful, for example, when you are selecting ({{@ColumnResult}}) as, e.g. a String.class, but want to use it as an argument of a {{ @ ConstructorResult}} which is a converted value. We could handle, e.g.:
{code}
@ConstructorResult(
Project.class,
columns={
...,
@ColumnResult( "status", MyStatusConverter.class )
}
)
enum Status {
...
}
class MyStatusConverter implements AttributeConverter<Status,String> {
...
}
class Project {
...
Project(..., Status status) { ...}
...
}
{code}
We could also implement "easy button" support for cases where we have a {{{ColumnResult}} with a {{#type}} of String or int used as the "JDBC type" used as an argument that to a {{ConstructorResult}} where the argument on the constructor is an enum. This would leverage our {{@Enumerated}} support. |
|
