Proper way to handle null values?

[unkreativ]

Hello,

As it bothers me checking null values repeatedly I've been wondering if Spring provides anything to deal with them. So far I've been using following class.

public class RowWrapper {

	private ResultSet resultSet;

	public RowWrapper(ResultSet resultSet) {
		if (resultSet == null) {
			throw new IllegalArgumentException("resultSet == null");
		}

		this.resultSet = resultSet;
	}

	public synchronized String getString(String columnLabel) throws SQLException {
		return checkNullValue(resultSet.getString(columnLabel));
	}

	public synchronized Double getDouble(String columnLabel) throws SQLException {
		return checkNullValue(resultSet.getDouble(columnLabel));
	}

	public synchronized Integer getInt(String columnLabel) throws SQLException {
		return checkNullValue(resultSet.getInt(columnLabel));
	}

	// ...

	private <T> T checkNullValue(T value) throws SQLException {
		if (resultSet.wasNull()) {
			return null;
		}

		return value;
	}
}

greets
Bernhard Huemer

EDIT: I guess I've misplaced this thread, sorry.

[Wesslan]

Some good old Spring AOP maybe?

[debasishg]

To address your concerns at a slightly broader perspective ..

a) Handling null validations like u have done in ur code snippet as :

    if (resultSet == null) {
            throw new IllegalArgumentException("resultSet == null");
    }

Jakarta Commons offer a nifty class org.apache.commons.lang.Validate, which helps you do so.

b) Handling null checks repeatedly can be done using the helper class that u have already written OR as suggested you can use AOP to weave this functionality.

c) For handling cases where you would like to have a uniform interfaces for handling null objects, think about using the Null Object pattern. This offers a nice way of handling nulls seamlessly and make your code look much better.

HTH.
- Debasish