Unique

```
@Target({TYPE,FIELD,METHOD})
@Retention(RUNTIME)
@Repeatable(Uniques.class)
public @interface Unique
```
Annotation for a database unique constraint. Used for database schema generation to create unique constraints. Also used to reorder database operations when flushing changes to avoid unique constraint violations. Corresponds to the xml element "unique".

Since:

2.1

Version:

2.1

Optional Element Summary

Optional Elements
Modifier and Type	Optional Element	Description
`Column[]`	`columns`	Columns that compose this unique constraint.
`java.lang.String`	`deferred`	Whether this unique constraint is deferred until commit.
`Extension[]`	`extensions`	Vendor extensions.
`java.lang.String[]`	`members`	Member (field and property) names that compose this unique constraint.
`java.lang.String`	`name`	Name of the unique constraint.
`java.lang.String`	`table`	Table for the unique constraint.

- Element Detail
  - name
```
java.lang.String name
```
    Name of the unique constraint.
    
    Returns:
    
    the name of the unique constraint
    
    Default:
    
    ""
- - table
```
java.lang.String table
```
    Table for the unique constraint. This is needed iff annotating a type where this unique constraint is not for the primary table for the persistent class or interface.
    
    Returns:
    
    the table on which the unique constraint is defined
    
    Default:
    
    ""
- - deferred
```
java.lang.String deferred
```
    Whether this unique constraint is deferred until commit.
    
    Returns:
    
    whether this unique constraint is deferred until commit
    
    Default:
    
    ""
- - members
```
java.lang.String[] members
```
    Member (field and property) names that compose this unique constraint.
    
    Returns:
    
    member names that compose this unique constraint
    
    Default:
    
    {}
- - columns
```
Column[] columns
```
    Columns that compose this unique constraint.
    
    Returns:
    
    columns that compose this unique constraint
    
    Default:
    
    {}
- - extensions
```
Extension[] extensions
```
    Vendor extensions.
    
    Returns:
    
    the vendor extensions
    
    Default:
    
    {}