How to use enum fields in JPA entity

What is this?

This is a demo of how to use enum fields in JPA entity. There are 3 approaches taken.

@Enumerated(EnumType.ORDINAL)

• This is the default mapping. Fragile, NOT recommended.
• You can't switch the order of the enum values without potentially damaging the data.
• The mapping is E <-> E.ordinal()

@Enumerated(EnumType.STRING)

• IMHO, this is usually the best approach. Simple, Flexible.
• The mapping is E <-> E.name()

Use a Converter that implements AttributeConverter<E, FieldType>

• This is the most flexible way, and definitely not simple.
• You can map it to pretty much any type of DB field.
• The mapping is E <- converter -> FieldType

Tech Stack

• Spring Boot
• Spring Data JPA
• Spring Web

How to run it

• Run the command: gradle clean build bootRun
• Open following URL in a browser: http://localhost:8080/h2-console
• Change the JDBC URL to: jdbc:h2:mem:testdb
• Click Connect to log in, and then examine the single row in the Ticket table

Notes

• It's always a good idea to have a table for each Enum type, so foreign key can be created to reference it.
• It's not easy to directly use an Enum type as a JPA entity mapping to a table.
• We can create a separate entity class, and then use a private field without property accessors to reference it.
• I have a preference for the mapping of Enum <-> 2-char string.