Sunday, March 27, 2011

Persistence of fields

The fields of the Entity will be saved in the database. JPA can use either your instance variables (fields) or the corresponding getters and setters to access the fields. You are not allowed to mix both methods. If you want to use the setter and getter methods the Java class must follow the Java Bean naming conventions. JPA persists per default all fields of an Entity, if fields should not be saved they must be marked with @Transient.
By default each field is mapped to a column with the name of the field. You can change the default name via @Column(name="newColumnName").
The following annotations can be used.

Annotations for fields / getter and setter
@Id Identifies the unique ID of the database entry
@GeneratedValue Together with ID defines that this value is generated automatically.
@Transient Field will not be saved in database

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