Configuring a Default Null Value at the Mapping 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 mapping level, TopLink uses it to translate in two directions:

When TopLink reads null from the data source, it converts this null to the specified type and value.
When TopLink writes or queries to the data source, it converts the specified type and value back to null.

Table 35-6 summarizes which mappings support this option.

Table 35-6 Mapping Support for Default Null Values

Mapping	Using TopLink Workbench	Using Java
Relational Mappings
Direct-to-Field Mapping
Direct to XMLType Mapping
EIS Mappings
EIS Direct Mapping
XML Mappings
XML Direct Mapping
XML Composite Direct Collection Mapping

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).

You can also use TopLink to set a default null value for all mappings used in a session (see "Configuring a Default Null Value at the Login Level").

Using TopLink Workbench

To configure a default null value for a mapping, use this procedure.

Select the mapped attribute in the Navigator. Its properties appear in the Editor.
Click the General tab. The General tab appears.

Figure 35-6 General Tab, Default Null Value Options

Description of "Figure 35-6 General Tab, Default Null Value Options"

Use the following information to complete the Default Null Value fields on the tab:

Field	Description
Default Null Value	Specify if this mapping contains a default value in the event that the data source is `null`. If selected, you must enter both the Type and Value of the default.
Type	Select the Java type of the default value.
Value	Enter the default value.

Using Java

To configure a mapping null value using Java API, use the AbstractDirectMapping method setNullValue.

For example:

// Defaults a null salary to 0
salaryMapping.setNullValue(new Integer(0));