Java Reference
In-Depth Information
can't be obtained from
EntityManager
or
EntityManagerFactory
, the objects our test
case has references to. To overcome this limitation, we need our first hack: using an
Ant task (
JPAConfigurationTask
), which is also part of Hibernate Tools.
This is where the schema is effectively generated. The problem is,
SchemaExport
either exports it to the system output or to a file. Ideally, it should allow the schema to
be exported to a
Writer
or
OutputStream
object, so we could pass a
StringWriter
as
a parameter to this method. Because this isn't the case, we have to use a second hack:
replace the
System.out
when this method is executed and then restore it afterwards.
Yes, we know this is ugly, but we warned you.
A final hack: because
JPAConfigurationTask
's
createConfiguration()
method is
protected, our test case won't have access to it, so we create a subclass and override
that method, making it accessible to classes in the same package.
D
E
18.7
Summary
Using
ORM
tools (such as Hibernate and
JPA
) greatly simplifies the development of
database access code in Java applications. But regardless of how great the technology
is or how much it automates the work, it's still necessary to write test cases for code
that uses it.
A common practice among Java
EE
applications is to use Façades and
DAO
s in the
business and persistence layers (respectively). In this chapter, we showed how to test
these layers in isolation, using mocks as
DAO
implementation.
We also showed how to leverage DbUnit and advanced techniques to effectively
test the
JPA
-based persistence layer, first testing the entity mappings and then the
DAO
s, properly speaking. We also demonstrated how to use
JPA
-generated
ID
s in your
DbUnit datasets.
And although
JPA
testing is an extension of database testing (which was covered in
chapter 17), it has its caveats, such as lazy initialization exceptions, duplicated objects
returned in queries, cascade deletes, and generation of weird constraint names. The
examples in this chapter demonstrated how to deal with such issues.
