Using enums in java

Question

I created an Enum and I need to set the values in the bank that way:

• If it is Revenue, the value is 0;
• If it is Expense, the value is 1;

This is my Enum:

 public enum EntryType {
   INCOME, OUTPUT;
 }

In my java controller, the type comes as String, because I’m getting the value of a radio button:

  <input type="radio" name="income" id="radio-income" value="INCOME"
  ng-model="entry.type">
  <label for="radio-income"><span></span>Entrada</label>

  <input type="radio" name="output" id="radio-output" value="OUTPUT" 
  ng-model="entry.type">
  <label for="radio-output"><span></span>Saída</label>

That’s the definition of Entrytype in my entity:

@Enumerated(EnumType.STRING)  // Ja tentei com EnumType.Ordinal
@Column(name = "type")
private EntryType type;

How do I take the Enum ordinal value to set in the database, instead of setting the string?

Answer 1

I don’t recommend using the ordinal enum as her identifier in the database. If you do this, adding a new element in the enumeration that is not at the end or reordering them will generate an inconsistency in your database since the ordinal will change. Example:

Suppose you have the following enumeration:

public enum User Role {
    
    REGISTERED_USER, ADMIN;
}

In this case, in your database you would have users with the privilege REGISTERED_USER with the value 0 and ADMIN value 1. Now suppose you add a new UserRole:

public enum UserRole {
    
    REGISTERED_USER, GUEST, ADMIN;
}

From now on, REGISTERED_USER has a value of 0, GUEST has a value of 1 and ADMIN the value 2. That is, all ADMIN became GUEST!

Solution:

What you can do is assign a id to each element and implement a AttributeConverter. That way, for every new element you add, just assign a new identifier that doesn’t need to be sequential.

Entrytype.java

public enum EntryType {
    INCOME(0), 
    
    OUTPUT(1);
    
    //para uso interno
    //evita que arrays sejam criados desnecessariamente
    private static final EntryType VALUES[] = EntryType.values();
    
    private final int identificador;
    
    private EntryType(int identificador) {
        this.identificador = identificador;
    }
    
    public final int getIdentificador() {
        return identificador;
    }
    
    //Caso queira, pode retornar um optional ao invés de lançar um exceção
    public static final EntryType deIdentificador(int identificador) {
        for(EntryType et : VALUES) {
            if(et.identificador == identificador) {
                return et;
            }
        }
        throw new IllegalArgumentException("identificador inválido: " + identificador);
    }
}

Entrytypeconverter

public final class EntryTypeConverter implements AttributeConverter<EntryType, Integer> {

    @Override
    public final Integer convertToDatabaseColumn(EntryType attribute) {
        return attribute.getIdentificador();
    }

    @Override
    public final EntryType convertToEntityAttribute(Integer dbData) {
        return EntryType.deIdentificador(dbData);
    }

}

In its entity:

@Column(name = "type")
@Convert(converter=EntryTypeConverter.class)
private EntryType type;