Getting Boolean from ResultSet

Question

ResultSet#getBoolean seems to return false when it's null.
Is there an easy way to get a Boolean (not boolean) from a ResultSet?

Ryeland

Answer 1

You can call wasNull after calling getBoolean. It's explained here: https://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html#wasNull%28%29

Marceau

So I'd have to use: Boolean foo = result.getBoolean("bar"); if (result.wasNull()) foo = null;? – Ryeland

Yes, you can use it like that. – Marceau

Thanks, great help – Timothea

Answer 2

This should work:

    try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/test?serverTimezone=UTC");){

        // create table bool_table (bool_value boolean);
        // insert into bool_table values (null);
        String sql = "SELECT * FROM bool_table";

        try (PreparedStatement preStmt = conn.prepareStatement(sql)){

            try (ResultSet rs = preStmt.executeQuery()) {
                rs.next();

                System.out.println(rs.getObject(1, Boolean.class));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    } catch (SQLException ex) {
        ex.printStackTrace();
    }

Cholecyst

It throws java.lang.AbstractMethodError – Exothermic

@NadavB, that shouldn't be the case, at least for MySQL. I added a full example. – Cholecyst

it happened to me with postgresql. The second answer with the wasNull worked for me fine. So maybe your answer is only for mySQL? – Exothermic

@NadavB, yes, as the original question was related to MySQL only. – Cholecyst

This will also return false when the DB column is null, which is what the OP was trying to avoid. – Ligate

This solution worked very well for me, using AS400/DB2. Thanks Alexey! – Humoresque

Answer 3

You should get the desired result (ie: null when the column value is null) by using ResultSet.getObject() and then casting to a Boolean Object.

Like this:

Boolean someBool = (Boolean) rs.getObject("booleanColumnName");

I think this is safe as long as your column type corresponds to boolean (ie: TINYINT(1)), But test it.

This answer does the same thing but with the Integer Object.

Ligate

Integer cannot be casted to Boolean. – Timmy

You're casting an Object to Boolean. docs.oracle.com/javase/7/docs/api/java/sql/… – Ligate

The type of the Java object will be the default Java object type corresponding to the column's SQL type. Read about casting. – Timmy

In Oracle there is no boolean column, but method getBoolean is working. – Timmy

Answer 4

resultSet.getObject(1) == null ? null : resultSet.getBoolean(1)

Timmy

Answer 5

You can use java optional for that:

    public static Boolean getNullableBoolean(ResultSet rs, String column) throws SQLException {
        return Optional.ofNullable((Boolean)rs.getObject(column))
                       .map(Boolean::booleanValue).orElse(null);
    }

...

getNullableBoolean(rs, "my_boolean_column")

Nowt

This is redundant -- you are converting a Boolean to a boolean with "booleanValue()", then converting it back again by returning it to a boxed Boolean context. Your code is entirely equivalent to doing return (Boolean)rs.getObject(column). HTH! – Redraft