Oracle8i SQLJ Developer's Guide and Reference Release 8.1.5 A64684-01 |
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Weakly typed objects, references, and collections are supported by SQLJ. Their general use is not recommended and there are some specific restrictions, but in some circumstances they may be useful. For example, you may have generic code that can use "any STRUCT
" or "any REF
" (although if this uses dynamic SQL it would require coding in JDBC instead of SQLJ).
In using Oracle objects, references, or collections in a SQLJ application, you have the option of using generic and weakly typed oracle.sql
classes instead of the strongly typed custom Java classes that implement the CustomDatum
interface.
The following oracle.sql
classes can be used for iterator columns or host expressions in Oracle SQLJ:
In host expressions they are supported as follows:
Using these classes is not generally recommended, however, as you would lose all the advantages of the strongly typed paradigm that SQLJ offers.
Each attribute in a STRUCT
object or each element in an ARRAY
object is stored in an oracle.sql.Datum
object, with the underlying data being in the form of the appropriate oracle.sql.*
type (such as oracle.sql.NUMBER
or oracle.sql.CHAR
). Attributes in a STRUCT
object are nameless.
Because of the generic nature of the STRUCT
and ARRAY
classes, SQLJ cannot do type checking where objects or collections are written to or read from instances of these classes.
It is generally recommended that you use custom Java classes for objects, references, and collections, preferably classes generated by JPublisher.
A weakly typed object (STRUCT
instance), reference (REF
instance), or collection (ARRAY
instance) cannot be used in host expressions in the following circumstances:
IN
parameter if null
OUT
or INOUT
parameter in stored procedure or function call
OUT
parameter in stored function result-expression
They cannot be used in these ways because there is no way to know the underlying SQL type name (such as Person
), which is required by the Oracle JDBC driver in order to materialize an instance of a user-defined type in Java.