Tell Hibernate's hbm2ddl to add MySQL enum columns for @Enumerated annotated fields

Question

I'm creating a DB table using hbm2ddl with Java code similar to the following:

@Entity
public  class Filter {
    public enum Type {
        TypeA, TypeB;
    }
    @Enumerated(EnumType.STRING)
    private Type type;
}

It works fine, but for "type" a VARCHAR column is created, i.e. the DDL code looks like this:

CREATE TABLE IF NOT EXISTS `filter` (`type` varchar(255) DEFAULT NULL)

But what I want to have is this:

CREATE TABLE IF NOT EXISTS `filter` (`type` enum('TypeA','TypeB') NOT NULL)

Is this possible to declare in Hibernate, preferred with annotations?

Or is there a way to extend SchemaUpdate and overwrite the method that renders the alter script part for enumerated field the way I like it?

Background: The same database is used in a PHP part of the project and I want to prevent that invalid values are inserted.

Answer 1

I believe that's going to be complicated, since the java.sql.Types, which define the sql types treated by java, does not have enum type (since it's not a standardized type according to SQL-92).

If that was the case you could create a hibernate custom UserType extending the EnumType and setting the sqlType accordingly, but since java.sql.Types doesn't handle it I don't see how to use native sql enum.

best regards!

Answer 2

Although it seems there is no way to handle MySQL enums 100% automatically, as pointed out by Lucas on his answer, there is actually a simple way to contour it. You may use columnDefinition attribute on @Column annotation, which seems to be specifically designed to generate custom DDL code.

See the documentation excerpt describing the attribute:

(Optional) The SQL fragment that is used when generating the DDL for the column.

Defaults to the generated SQL to create a column of the inferred type.

The NOT NULL restriction is quite standard, and is supported by another attribute nullable.

Thus, your property definition would look like this:

@Enumerated(EnumType.STRING)
@Column(columnDefinition = "enum ('TypeA', 'TypeB')", nullable = false)
private Type type;