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?

Solution 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

Solution 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();
    }

Solution 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.

Solution 4

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

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Comments

[Priv]

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

[uoyilmaz]

Yes, you can use it like that.

[Nathan B]

It throws java.lang.AbstractMethodError

[Alexey Soshin]

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

[Nathan B]

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

[Alexey Soshin]

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

[leole]

Thanks, great help

[theyuv]

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

[Alex78191]

Integer cannot be casted to Boolean.

[theyuv]

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

[Alex78191]

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

[Alex78191]

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

[jfajunior]

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