StringEnum enum example

Book.java

@Entity
@TypeDef(name = "string-enum", typeClass = StringEnumType.class)
public class Book {
	
  @Id
  private String bookId;
	
  @Enumerated(EnumType.STRING)
	@Type(type="string-enum")
	private BookType bookType;
  
  private String title;
  
} 

BookType.java

public enum BookType implements StringEnum {
  SCIENCE_FICTION("Science fiction"),
	Drama("Drama"),
  ACTION_ADVENTURE("Action and Adventure")
  }

StringEnum.java

/**
 * <p>Enumerations that override toString and provide a fromString method can
 * implement this interface. Implementers can annotate the use of their type
 * with StringEnumType class, allowing for more seamless conversion to and from
 * a PostgreSQL Enum field type.</p>
 * 
 * <p>Note: Implementing classes are expected to implement a static `fromString`
 * method and override toString. Interfaces do not allow you to specify a static
 * modifier.</p>
 * 
 * <p>Recommended static `fromString` method. This assumes desired behavior of returning a 'default' value.</p>
 * 
 * <pre>
 * 	public static MyEnum fromString(String representation) {
 *		return Arrays.stream(values()).filter(value -> value.toString().equals(representation)).findFirst()
 *				.orElse(getDefault());
 *	}
 * </pre>
 * 
 *
 */
public interface StringEnum {

}

StringEnumType.java

/**
 * Provides a way to have a string read and written using Hibernate.
 * 
 * NOTE: The PostgresEnumType does not work with Enums having a string value
 * 
 *
 */
public class StringEnumType extends org.hibernate.type.EnumType {

	private static final long serialVersionUID = -7372724879821833735L;

	public void nullSafeSet(
            PreparedStatement st,
            Object value,
            int index,
            SessionImplementor session)
            throws HibernateException, SQLException {
        if (value == null) {
            st.setNull(index, Types.OTHER);
        } else {
            st.setObject(index, value.toString(), Types.OTHER);
        }
    }
    
	
	@Override
	public Object nullSafeGet(ResultSet rs, String[] names, SharedSessionContractImplementor session, Object owner)
			throws SQLException {
        String representation = rs.getString(names[0]);
        if (rs.wasNull()) {
            return null;
        }
        for (Enum<?> value : returnedClass().getEnumConstants()) {
            if (value instanceof StringEnum) {
                StringEnum stringEnum = (StringEnum) value;
                if (stringEnum.toString().equals(representation)) {
                    return value;
                }
            }
        }
        throw new IllegalStateException("Unknown " + returnedClass().getSimpleName() + " string");
    }
}