9.12.1 Defining the mapping between an entity class and database

An entity class is mapped to a line in the database table. The fields stored in the entity class are mapped to the values in the table columns. If the user updates a field value for an entity class instance, Cosminexus JPA Provider also updates the corresponding column of the database table. Therefore, the user can change the database state without issuing an SQL statement for the database.

The following figure shows the mapping between an entity class and a database table.

Figure 9‒22: Mapping between the entity class and database table

You define the correspondence relationship between the entity fields and database columns in an annotation or the O/R mapping file. You can define the correspondence in either an annotation or the O/R mapping file. However, if the definition is specified in both, the settings in the O/R mapping file are given priority over the annotation. If different values are specified for the same settings in the annotation and the O/R mapping file, the value in the annotation is overwritten with the value in the O/R mapping file.

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