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Oracle TopLink Developer's Guide 10g Release 3 (10.1.3) B13593-01 |
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# Configuring a Default Null Value at the Login Level

A default null value is the Java `Object` type and value that TopLink uses instead of `null` when TopLink reads a `null` value from a data source.

When you configure a default null value at the login level, it applies to all mappings used in a session. In this case, TopLink uses it to translate in one direction only: when TopLink reads `null` from the data source, it converts this `null` to the specified type and value.

You can also use TopLink to set a default null value on a per-mapping basis (see "Configuring a Default Null Value at the Mapping Level").

Note: A default null value must be an `Object`. To specify a primitive value (such as `int`), you must use the corresponding `Object` wrapper (such as `Integer`).

## Using Java

Using Java API, you can configure a default null value for all mappings used in a session with the `DatabaseLogin` method `setDefaultNullValue(Class,Object)`.

For example:

    // Defaults all null String values read from the database to empty String
    session.getLogin().setDefaultNullValue(String, "");