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Enumerated

layout: default title: @Enumerated

You may want to map a particular database column onto a Java enum.

  • For example, a gender column would have a small number of allowable values.

By default, JPA will attempt to store the ordinal value for your enum into the database.

  • The ordinal value is a zero-based incrementing number where the first value in your enum is zero, the second is one, and so on.

Most of the time it would be better to store the actual enum name, instead.

  • Annotate your entity's field (not the enum itself) with @Enumerated(EnumType.STRING) to override the default ordinal behavior.
@Enumerated(EnumType.STRING)
private Gender gender;

Drill

  1. Create a new enum called Rating in the entities package and add the following values:
  2. G, PG, PG13, R, NC17
    Rating Enum
  3. Next, modify your Film entity and add a new field for the film’s rating.
  4. Don’t forget to annotate the field with @Enumerated and provide the EnumType.String
  5. Generate get/set methods.

For reference, here is the film table: 

+------------------+---------------------------------------------------------------------+------+-----+---------+----------------+
| Field            | Type                                                                | Null | Key | Default | Extra          |
+------------------+---------------------------------------------------------------------+------+-----+---------+----------------+
| id               | int(10) unsigned                                                    | NO   | PRI | NULL    | auto_increment |
| title            | varchar(255)                                                        | NO   | MUL | NULL    |                |
| description      | text                                                                | YES  |     | NULL    |                |
| release_year     | year(4)                                                             | YES  |     | NULL    |                |
| language_id      | smallint(5) unsigned                                                | NO   | MUL | NULL    |                |
| rental_duration  | tinyint(3) unsigned                                                 | NO   |     | 3       |                |
| rental_rate      | decimal(4,2)                                                        | NO   |     | 4.99    |                |
| length           | smallint(5) unsigned                                                | YES  |     | NULL    |                |
| replacement_cost | decimal(5,2)                                                        | NO   |     | 19.99   |                |
| rating           | enum('G','PG','PG13','R','NC17')                                    | YES  |     | G       |                |
| special_features | set('Trailers','Commentaries','Deleted Scenes','Behind the Scenes') | YES  |     | NULL    |                |
+------------------+---------------------------------------------------------------------+------+-----+---------+----------------+

  1. Modify your FilmTest class, write a test called films_have_ratings which ensures that a given film has the expected rating.

  2. Don't forget, the returned value you are testing for will be an enum, not a String.

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