How To Calculate An Entity Persistent Property At INSERT Or UPDATE Time Via Hibernate @Generated
Description: This application is an example of calculating an entity persistent property at INSERT or UPDATE time via Hibernate @Generated annotation.
Key points:
- annotate the entity persistent field that corresponds to the property that should be calculated with @Generated(value = GenerationTime.ALWAYS) or @Generated(value = GenerationTime.INSERT)
- annotate the same field with @Column(insertable = false, updatable = false)
- if the database schema is generated via JPA annotations (not recommended) then use columnDefinition element of @Column to specify the formula
- if the database schema is not generated via JPA annotations (recommended way) then add the formula as part of schema in CREATE TABLE
Note: In production, you should not rely on columnDefinition. You should disable hibernate.ddl-auto (by omitting it) or set it to validate, and add the SQL query expression in CREATE TABLE (in this application, check the discount column in CREATE TABLE, file schema-sql.sql). Nevertheless, not even schema-sql.sql is ok in production. The best way is to rely on Flyway or Liquibase.
