The unique=true
element of the Column
annotation and / or the UniqueConstraint
annotation that can be used at the table level are used to specify that a unique constraint is to be included in the generated DDL.
In other words, they don't do anything during the runtime, the verification is left to the database (which makes sense as unicity can't be tested at the Java level reliably1) and if for whatever reason you don't have the corresponding constraint(s) defined at the database level, nothing will happen.
Add the constraint manually:
ALTER TABLE Customer ADD CONSTRAINT customer_name_unq UNIQUE (name);
See also
- JPA 1.0 specification
- 9.1.4 UniqueConstraint Annotation
- 9.1.5 Column Annotation
- MySQL Documentation
1 Unless you acquire a table lock (ouch!), you can't check for unicity with a SQL query in a concurrent environment.
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