Java Reference
In-Depth Information
■
Note
if an application utilizes FUnCtiOn invocation, it may not be portable across databases.
Bulk Updates and Deletions
The Criteria API has been enhanced to support bulk updates and deletions. The Criteria API allows developers to
utilize Java language syntax in order to perform database queries and manipulations, rather than JPQL or SQL.
A
javax.persistence.criteria.CriteriaUpdate
object can be used to perform bulk update operations, and a
javax.persistence.critera.CriteriaDelete
object can be used to perform bulk deletion operations. How do
we obtain such objects? The Criteria API is dependent upon the
javax.persistence.criteria.CriteriaBuilder
interface, which is used to return objects that can be used to work with specified Entity classes. In the JPA 2.1 release,
the
CriteriaBuilder
has been updated to include the methods
createCriteriaUpdate
and
createCriteriaDelete
,
which will return the
CriteriaUpdate
or
CriteriaDelete
objects, respectively.
To make use of the
CriteriaBuilder
, you first need to obtain a
CriteriaBuilder
from the
EntityManager
. You
can then use the
CriteriaBuilder
to obtain the
CriteriaUpdate
or
CriteriaDelete
object of your choosing. In the
following lines of code, a
CriteriaUpdate
object is obtained for use with an
Employee
entity.
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaUpdate<Employee> q = builder.createCriteriaUpdate(Employee.class);
Once obtained, the
CriteriaUpdate
can be used to build a query and set values, as desired, for making the
necessary updates or deletions. In the following excerpt, the
CriteriaUpdate
object is used to update all
Employee
objects that have a status of
INACTIVE
, changing that status to
ACTIVE
.
Root<Employee> e = q.from(Employee.class);
q.set(e.get("status"), "ACTIVE")
.where(builder.equal(e.get("status"), "INACTIVE"));
Let's break this down a bit to explain what exactly is going on. First, the query root is set by calling the
q.from
method and passing the entity class for which we wish to obtain the root, where
q
is the
CriteriaUpdate
object. Next,
the
q.set
method is invoked, passing the
Path
to the
Employee status
attribute, along with the
ACTIVE
String. The
q.set
method is performing the bulk update. To further refine the query, a
WHERE
clause is added by adding a chained
call to the
.where
method, and passing the
Employee
objects that have a status of
INACTIVE
. To see an entire example,
please visit the
org.javaee7.chapter04.jsf.CriteriaUpdates
class. The entire Criteria update looks as follows:
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaUpdate<Employee> q = builder.createCriteriaUpdate(Employee.class);
Root<Employee> e = q.from(Employee.class);
q.set(e.get("status"), "ACTIVE")
.where(builder.equal(e.get("status"), "INACTIVE"));
Finally, to complete the transaction, you must create the
Query
object and then execute it using the following
lines of code:
Query criteriaUpd = em.createQuery(q);
criteriaUpd.executeUpdate();
The complete code for the bulk update in this example resides within a method named
updateEmployeeStatusInactive
, which is listed below.
