How to map column with type BIT(24) in PostgreSQL with Hibernate

I have a table with a column which type is a bit (24). I tried to use String and when I try to get this object it maps well, but when I try to save it, Hibernate throws Exception: org.postgresql.util.PSQLException: ERROR: column is of type bit but expression is of type character varying

I know that if it’s a bit(1) I can use Boolean, but I don’t know what should I do in my case.

Thanks in advance!

Answer

Unfortunately, JPA/hibernate does not support BIT having a parametrized length.

Fortunately, you can define your own custom type with hibernate.

First, you need to create BitStringType, BitStringJavaDescriptor, and BitStringSqlDescriptor:

public class BitStringType extends AbstractSingleColumnStandardBasicType<String> {

    public static final BitStringType INSTANCE = new BitStringType();

    public BitStringType() {
        super(VarcharTypeDescriptor.INSTANCE, BitStringJavaDescriptor.INSTANCE);
    }

    @Override
    public String getName() {
        return "BitString";
    }

}

public class BitStringJavaDescriptor extends AbstractTypeDescriptor<String> {

    public static final BitStringJavaDescriptor INSTANCE = new BitStringJavaDescriptor();

    public BitStringJavaDescriptor() {
        super(String.class, ImmutableMutabilityPlan.INSTANCE);
    }

    @Override
    public String fromString(String string) {
        return string;
    }

    @Override
    public <X> X unwrap(String value, Class<X> type, WrapperOptions options) {
        if (value == null)
            return null;
        if (String.class.isAssignableFrom(type))
            return (X) value;
        throw unknownUnwrap(type);
    }

    @Override
    public <X> String wrap(X value, WrapperOptions options) {
        if (value == null)
            return null;
        if (String.class.isInstance(value))
            return (String) value;
        throw unknownWrap(value.getClass());
    }

}

public class BitStringSqlDescriptor implements SqlTypeDescriptor {

    public static BitStringSqlDescriptor INSTANCE = new BitStringSqlDescriptor();

    @Override
    public int getSqlType() {
        return Types.OTHER;
    }

    @Override
    public boolean canBeRemapped() {
        return true;
    }

    @Override
    public <X> ValueBinder<X> getBinder(final JavaTypeDescriptor<X> javaTypeDescriptor) {
        return new BasicBinder<X>(javaTypeDescriptor, this) {
            @Override
            protected void doBind(PreparedStatement st, X value, int index, WrapperOptions options) throws SQLException {
                st.setObject(index, javaTypeDescriptor.unwrap(value, String.class, options), Types.OTHER);
            }
            @Override
            protected void doBind(CallableStatement st, X value, String name, WrapperOptions options) throws SQLException {
                st.setObject(name, javaTypeDescriptor.unwrap(value, String.class, options), Types.OTHER);
            }
        };
    }

    @Override
    public <X> ValueExtractor<X> getExtractor(final JavaTypeDescriptor<X> javaTypeDescriptor) {
        return new BasicExtractor<X>(javaTypeDescriptor, this) {
            @Override
            protected X doExtract(ResultSet rs, String name, WrapperOptions options) throws SQLException {
                return javaTypeDescriptor.wrap(rs.getString(name), options);
            }
            @Override
            protected X doExtract(CallableStatement statement, int index, WrapperOptions options) throws SQLException {
                return javaTypeDescriptor.wrap(statement.getString(index), options);
            }
            @Override
            protected X doExtract(CallableStatement statement, String name, WrapperOptions options) throws SQLException {
                return javaTypeDescriptor.wrap(statement.getString(name), options);
            }
        };
    }

}

Having those classes, you can define a type for your field. Please, use the correct package (in my case I’ve used the one from my demo com.yonlabs.jpa):

    @Column
    @Type(type = "com.yonlabs.jpa.BitStringType")
    private String bits;

You can also register this type with hibernate to use a registered name instead of a fully qualified Java class.