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?

score 19 · Accepted Answer · answered Sep 18 '16 at 18:25

19

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

answered Sep 18 '16 at 18:25

uoyilmaz

3,035
14
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So I'd have to use: `Boolean foo = result.getBoolean("bar"); if (result.wasNull()) foo = null;`? – Priv Sep 18 '16 at 18:27
Yes, you can use it like that. – uoyilmaz Sep 18 '16 at 18:27
Thanks, great help – leole Jul 10 '17 at 07:09

Alexey Soshin · Answer 2 · 2017-03-24T10:41:08.980

8

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();
    }

edited Mar 24 '17 at 10:41

answered Sep 18 '16 at 18:25

Alexey Soshin

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It throws java.lang.AbstractMethodError – Nathan B Mar 22 '17 at 16:14
@NadavB, that shouldn't be the case, at least for MySQL. I added a full example. – Alexey Soshin Mar 24 '17 at 10:40
it happened to me with postgresql. The second answer with the wasNull worked for me fine. So maybe your answer is only for mySQL? – Nathan B Mar 25 '17 at 18:04
@NadavB, yes, as the original question was related to MySQL only. – Alexey Soshin Mar 26 '17 at 15:57
1

This will also return false when the DB column is null, which is what the OP was trying to avoid. – theyuv Apr 03 '19 at 14:16
This solution worked very well for me, using AS400/DB2. Thanks Alexey! – jfajunior Jul 01 '19 at 12:33

score 4 · Answer 3 · answered Apr 03 '19 at 14:27

4

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.

answered Apr 03 '19 at 14:27

theyuv

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`Integer` cannot be casted to `Boolean`. – Alex78191 Jun 10 '19 at 15:43
You're casting an `Object` to `Boolean`. https://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html#getObject(int) – theyuv Jun 10 '19 at 15:45
`The type of the Java object will be the default Java object type corresponding to the column's SQL type`. Read about casting. – Alex78191 Jun 10 '19 at 15:48
1

In Oracle there is no boolean column, but method getBoolean is working. – Alex78191 Jun 20 '19 at 16:20

score 4 · Answer 4 · answered Jun 10 '19 at 18:07

4

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

answered Jun 10 '19 at 18:07

Alex78191

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score 0 · Answer 5 · answered Dec 07 '22 at 23:46

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")

Getting Boolean from ResultSet

5 Answers5