THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Overview
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This example shows how to create a Stateless session EJB using annotations. As stated in the "JSR 220: Enterprise JavaBeansTM,Version 3.0 - EJB Core Contracts and Requirements",
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"Stateless session beans are session beans whose instances have no conversational state. This means that all bean instances are equivalent when they are not involved in servicing a client-invoked method. The term 'stateless' signifies that an instance has no state for a specific client."
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What this means is quite simply that stateless beans are *shared*. They do in fact have state as you can assign values to the variables, etc. in the bean instance. The only catch is there are a *pool* of identical instances and you are not guaranteed to get the exact same instance on every call. For each call, you get whatever instance happens to be available. This is identical to checking out a book from the library or renting a movie from the video store. You are essentially checking out or renting a new bean instance on each method call.
With EJB 3.0, it's now possible to write stateless session bean without specifying a deployment descriptor; you basically have to write just a remote or local business interface, which is a plain-old-java-interface, annotated with the @Remote or @Local annotation the stateless session bean implementation, a plain-old-java-object which implements the remote or the local business interface and is annotated with the @Stateless annotation
_This example is the "simple-stateless" example located in the [openejb-examples.zip|OPENEJB:Download] available on the download page._
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{div:style=clear:both;}{div} h1. |
The
...
Code
...
In
...
this
...
example
...
we
...
develop
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a
...
simple
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EJB
...
3
...
Stateless
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session
...
EJB.
...
Every
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stateless
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session
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bean
...
implementation
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must
...
be
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annotated
...
using
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the
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annotation
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@Stateless
...
or
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marked
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that
...
way
...
in
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the
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ejb-jar.xml
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file.
...
Our
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Stateless
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bean
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has
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2
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business
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interfaces:
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CalculatorRemote,
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a
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remote
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business
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interface,
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and
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CalculatorLocal,
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a
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local
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business
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interface.
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A
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minimum
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of
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one
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business
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interface
...
is
...
required.
Bean
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h2. Bean {snippet:id=code|url=openejb3/examples/simple-stateless/src/main/java/org/superbiz/calculator/CalculatorImpl.java|lang=java} |
In
...
EJB
...
3.0
...
session
...
beans
...
do
...
not
...
need
...
to
...
implement
...
the
...
javax.ejb.SessionBean
...
interface.
...
You
...
can
...
simply
...
annotate
...
it
...
as
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@Stateless
...
if
...
you
...
want
...
it
...
to
...
be
...
a
...
stateless
...
session
...
bean.
...
Users
...
of
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EJB
...
2.x
...
may
...
notice
...
the
...
bean
...
actually
...
implements
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the
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business
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interfaces!
...
In
...
the
...
prior
...
version
...
of
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EJB
...
implementing
...
the
...
remote
...
interface
...
(which
...
derives
...
from
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javax.ejb.EJBObject)
...
in
...
your
...
bean
...
was
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just
...
not
...
allowed.
...
Now
...
there
...
is
...
no
...
javax.ejb.EJBObject
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requirement,
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so
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implementing
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the
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business
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interfaces
...
is
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standard
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practice
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for
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EJB
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3.0.
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Local
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business interface
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interface {snippet:id=code|url=openejb3/examples/simple-stateless/src/main/java/org/superbiz/calculator/CalculatorLocal.java|lang=java} |
Local
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interfaces
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in
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EJB
...
are
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pass-by-reference
...
interfaces.
...
Meaning
...
that
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normal
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java
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semantics
...
are
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used
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for
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passing
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arguments,
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return
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values
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and
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exceptions.
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A
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business
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local
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interface
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can
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be
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any
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plain
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java
...
interface.
...
There
...
are
...
no
...
restrictions
...
on
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the
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method
...
arguments,
...
return
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types,
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or
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throws
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clauses.
...
Unless
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specified
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otherwise,
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every
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interface
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your
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bean
...
implements
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(and
...
it's
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parent
...
class
...
implements
...
and
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so
...
on)
...
is
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considered
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to
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be
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a
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local
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business
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interface.
...
You
...
can
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use
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the
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@Local
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annotation
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to
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explicitly
...
state
...
that
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an
...
interface
...
is
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a
...
local
...
interface,
...
but
...
this
...
is
...
not
...
required.
...
You'll
...
notice
...
that
...
in
...
EJB
...
3.0
...
the
...
Local
...
Business
...
Interface
...
of
...
a
...
stateless
...
session
...
bean
...
does
...
not
...
need
...
to
...
extend
...
from
...
javax.ejb.EJBLocalObject
...
and
...
does
...
not
...
need
...
a
...
javax.ejb.EJBLocalHome
...
interface
...
as
...
they
...
did
...
in
...
EJB
...
2.x
...
and
...
prior.
...
Per
...
the
...
vocabulary
...
of
...
the
...
EJB
...
spec,
...
interfaces
...
that
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implement
...
javax.ejb.EJBLocalObject
...
or
...
javax.ejb.EJBLocalHome
...
are
...
considered
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Component
...
Interfaces
...
and
...
the
...
plain
...
java
...
interface
...
above
...
is
...
considered
...
a
...
Business
...
Interface.
...
Remote
...
business interface
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interface {snippet:id=code|url=openejb3/examples/simple-stateless/src/main/java/org/superbiz/calculator/CalculatorRemote.java|lang=java} |
Remote
...
interfaces
...
are
...
pass-by-value
...
interfaces.
...
Meaning
...
that
...
all
...
method
...
parameters,
...
return
...
values,
...
and
...
exceptions
...
are
...
serialized
...
on
...
every
...
call.
...
The
...
result
...
is
...
that
...
you
...
get
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a
...
copy
...
of
...
the
...
original
...
object
...
and
...
not
...
the
...
original
...
object.
...
The
...
advantage
...
is
...
of
...
course
...
that
...
Remote
...
interfaces
...
can
...
be
...
used
...
to
...
invoke
...
an
...
EJB
...
across
...
a
...
network
...
in
...
a
...
client-server
...
fashion.
...
There
...
are
...
no
...
restrictions
...
on
...
the
...
Remote
...
interface
...
itself,
...
but
...
there
...
are
...
on
...
the
...
data
...
passed
...
in
...
and
...
out
...
of
...
the
...
remote
...
interface.
...
The
...
values
...
passed
...
into
...
a
...
method
...
or
...
returned
...
from
...
a
...
method
...
of
...
a
...
Remote
...
interface
...
must
...
be
...
serializable
...
.
...
It
...
is
...
fine
...
for
...
the
...
method
...
signature
...
to
...
be,
...
for
...
example,
...
"public
...
Object
...
myMethod(Object
...
myParam)"
...
as
...
long
...
as
...
the
...
value
...
passed
...
in
...
and
...
returned
...
implements
...
java.io.Serializable
...
.
...
As
...
stated
...
above,
...
the
...
Remote
...
Business
...
Interface
...
of
...
a
...
bean
...
can
...
be
...
any
...
plain
...
old
...
interface.
...
It
...
does
...
not
...
need
...
to
...
extend
...
javax.ejb.EJBObject,
...
it
...
does
...
not
...
need
...
a
...
javax.ejb.EJBHome,
...
the
...
methods
...
do
...
not
...
need
...
to
...
throw
...
javax.rmi.RemoteException,
...
and
...
the
...
bean
...
class
...
can
...
implement
...
it!
...
At
...
minimum
...
the
...
interface
...
must
...
be
...
annotated
...
with
...
@Remote
...
either
...
in
...
the
...
interface
...
itself
...
or
...
in
...
the
...
bean
...
class,
...
or
...
the
...
interface
...
must
...
be
...
declared
...
via
...
<business-remote>
...
in
...
the
...
ejb-jar.xml.
...
Writing
...
a
...
unit
...
test
...
for
...
the
...
example
...
Writing
...
an
...
unit
...
test
...
for
...
the
...
stateless
...
session
...
EJb
...
is
...
quite
...
simple.
...
We
...
need
...
just
...
to
...
write
...
a
...
setup
...
method
...
to
...
create
...
and
...
initialize
...
the
...
InitialContext,
...
and
...
then
...
write
...
our
...
test
...
methods
setUp
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h2. setUp {snippet:id=setup|url=openejb3/examples/simple-stateless/src/test/java/org/superbiz/calculator/CalculatorTest.java|lang=java} h2. |
Test
...
the
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local
...
business interface
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interface {snippet:id=local|url=openejb3/examples/simple-stateless/src/test/java/org/superbiz/calculator/CalculatorTest.java|lang=java} h2. |
Test
...
the
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remote
...
business interface
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interface {snippet:id=remote|url=openejb3/examples/simple-stateless/src/test/java/org/superbiz/calculator/CalculatorTest.java|lang=java} { |
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Note that JNDI names for Java SE clients are not standardized by the EJB spec. This is unfortunate and something being addressed in EJB 3.1. The default schema that OpenEJB uses is ejbName + interfaceType (i.e. Local, Remote, LocalHome, RemoteHome), so in our example "CalculatorImpl" + "Local" and "CalculatorImpl" + "Remote". You can in fact change this default to be absolutely [ |JNDI Names]including interface class name, ejb class name, and more. {info} h1. Running Running the example is fairly simple. In the |
Running
Running the example is fairly simple. In the "simple-stateless"
...
directory
...
of
...
the
...
...
...
,
...
just
...
run:
...
$
...
mvn
...
clean
...
install
...
Which
...
should
...
create
...
output
...
like
...
the
...
following.
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} ------------------------------------------------------- T E S T S ------------------------------------------------------- Running org.superbiz.calculator.CalculatorTest Apache OpenEJB 3.0 build: 20080408-04:13 http://openejb.apache.org/ INFO - openejb.home = /Users/dblevins/work/openejb-3.0/examples/simple-stateless INFO - openejb.base = /Users/dblevins/work/openejb-3.0/examples/simple-stateless INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service) INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager) INFO - Configuring Service(id=Default JDK 1.3 ProxyFactory, type=ProxyFactory, provider-id=Default JDK 1.3 ProxyFactory) INFO - Found EjbModule in classpath: /Users/dblevins/work/openejb-3.0/examples/simple-stateless/target/classes INFO - Configuring app: /Users/dblevins/work/openejb-3.0/examples/simple-stateless/target/classes INFO - Configuring Service(id=Default Stateless Container, type=Container, provider-id=Default Stateless Container) INFO - Auto-creating a container for bean CalculatorImpl: Container(type=STATELESS, id=Default Stateless Container) INFO - Loaded Module: /Users/dblevins/work/openejb-3.0/examples/simple-stateless/target/classes INFO - Assembling app: /Users/dblevins/work/openejb-3.0/examples/simple-stateless/target/classes INFO - Jndi(name=CalculatorImplLocal) --> Ejb(deployment-id=CalculatorImpl) INFO - Jndi(name=CalculatorImplRemote) --> Ejb(deployment-id=CalculatorImpl) INFO - Created Ejb(deployment-id=CalculatorImpl, ejb-name=CalculatorImpl, container=Default Stateless Container) INFO - Deployed Application(path=/Users/dblevins/work/openejb-3.0/examples/simple-stateless/target/classes) Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.845 sec Results : Tests run: 2, Failures: 0, Errors: 0, Skipped: 0 {noformat} |