Package org.hibernate.annotations
Annotation Interface ColumnTransformer
@Target({FIELD,METHOD})
@Retention(RUNTIME)
@Repeatable(ColumnTransformers.class)
public @interface ColumnTransformer
Specifies custom SQL expressions used to read and write to the column mapped by
the annotated persistent attribute in all generated SQL involving the annotated
persistent attribute.
- A
write()
expression must contain exactly one JDBC-style '?' placeholder. - A
read()
expression may not contain JDBC-style placeholders.
For example:
@Column(name="credit_card_num") @ColumnTransformer(read="decrypt(credit_card_num)" write="encrypt(?)") String creditCardNumber;
A column transformer write()
expression transforms the value of a persistent
attribute of an entity as it is being written to the database.
- If there is a matching
read()
expression to undo the effect of this transformation, then we're entitled to consider the in-memory state of the Java entity instance as synchronized with the database after a SQLinsert
orupdate
is executed. - On the other hand, if there's no matching
read()
expression, or if the read expression does not exactly undo the effect of the transformation, the in-memory state of the Java entity instance should be considered unsynchronized with the database after every SQLinsert
orupdate
is executed.
In the second scenario, we may ask Hibernate to resynchronize the in-memory state
with the database after each insert
or update
by annotating the
persistent attribute @Generated(event={INSERT,UPDATE}, writable=true)
.
This results in a SQL select
after every insert
or update
.
- See Also:
-
Optional Element Summary
Optional Elements
-
Element Details
-
forColumn
String forColumnThe name of the mapped column, if a persistent attribute maps to multiple columns. Optional if a persistent attribute is mapped to a single column- Default:
- ""
-
read
String readA custom SQL expression used to read from the column.- Default:
- ""
-
write
String writeA custom SQL expression used to write to the column. The expression must contain exactly one JDBC-style '?' placeholder.- Default:
- ""
-