April 2003
Beginner to intermediate
380 pages
12h 25m
English
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Transactional Fields
A JDO implementation manages two kinds of fields: persistent fields that are stored in the datastore and transactional fields . A transactional field is not persistent, but it participates in a transaction by having its values restored if a rollback occurs. Persistent and transactional fields are referred to collectively as managed fields . The state of a transactional field is saved before certain lifecycle-state transitions, so it can be restored if a transaction rollback occurs. The JDO implementation modifies a transactional field only during rollback for instances that have been modified by your application.
You specify that a field is transactional by setting its
persistence-modifier
attribute to "transactional" in the
metadata. A transactional field can be of any type; there are no
restrictions. The JDO implementation mediates the modification of a
transactional field, but it does not mediate field reads.
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