Configuring Mutable Mappings

Direct mappings typically map simple, non-mutable values such as String or Integer. Transformation mappings can potentially map complex mutable object values, such as mapping several database field values to an instance of a Java class.

If a transformation mapping maps a mutable value, TopLink must clone and compare the value in a unit of work (see "Configuring Copy Policy").

By default, TopLink assumes that all transformation mappings are mutable. If the mapping maps a simple nonmutable value, you can improve unit of work performance by configuring the IsMutable option to false.

Table 32-18 summarizes which mappings support this option.

Table 32-18 Mapping Support for Mutable Mappings

Mapping	Using TopLink Workbench	Using Java
Relational Mappings
Transformation Mapping
EIS Mappings
EIS Transformation Mapping
XML Mappings
XML Transformation Mapping

Using TopLink Workbench

Use this table to complete the Object->Field Method fields:

Select the mapped attribute in the Navigator. Its properties appear in the Editor.

Figure 32-19 Transformation Mapping, Mutable Option

Description of "Figure 32-19 Transformation Mapping, Mutable Option"

By default, the IsMutable option is selected in all transformation mappings. If the mapping maps to a simple atomic value, unselect this option.

Using Java

You can specify whether or not a mapping is mutable using AbstractTransformationMapping method setIsMutable.