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Re: [aspectj-users] A transaction question
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Hi Neo,
it should work, if you don't find the manager there it could be because
two different instances of AbstractTransaction aspect are intercepting
the two methods. This happens if you declared your aspect with a
specific instantiation rule.
By default, aspects are singletons. That means that there will be only
one instance of AbstractTransaction in your application (well, in your
classloader). Since this is sometimes a limit, AspectJ supports
different instantiation systems, like perthis, pertarget, percflow
etc... If you use one of these construct, then a new instance of your
aspect will be created for each "this", each "target" etc.. in this
case, when you use this.manager inside your aspect, it could be null
cause it is actually a different instance.
Could you post the complete aspect declaration, so that we can see which
instantiation rule you are using?
Hope this helps,
Simone
neo anderson wrote:
Thank you very much. Now I am able to obtain EntityManager whilst method
setEntityManager get called.
But a new question: how can I assign the captured variable e.g.
EntityManager to the variable in an Aspect? For instance,
... aspect AbstractionTransaction ...{
private EntityManager manager;
void around(EntityManager manager): obtainEntityManager(manager) &&
cflow(tx()){
System.out.println("manager:"+manager); // manager instance is not null
this.manager = manager; // but assign to the member of
aspect seemingly does not work
proceed(manager);
}
}
My AbstractTransaction aspect contains a variable manager and I would like
to assign when the setEntityManager get called. Because in the example of
Aspectj in Action, the method intercepted will return Connection, which is
different from the method I have. Is there any chance to assign the variable
so that I can apply entitymanager to the pointcut when scope() is executed?
Or what is the right way to do this?
Object around(): scope(){
System.out.println("===========> EntityManager:"+manager); // after
assigned, it is still null
Object result = proceed();
return result;
}
Sorry if this question is too newbie. I search on the internet and read
again the book Aspectj in Action, but seems there is no such explain.
Thanks for patiently answer my question.
I appreciate it.
Andy Clement wrote:
The method you are intercepting (setEntityManager) has a void return
type, so your advice should too. The proceed() call you are using
will ensure your replacement is passed to the setEntityManager call.
Andy
2009/11/4 neo anderson <javadeveloper999@xxxxxxxxxxx>:
Hi Mark & Andy. Thanks for your reply. I really appreciate your help.
I change to use args, but now it thorws message:
[error] incompatible return type applying to method-call(void
example.AccountDao.setEntityManager(example.EntityManager))
[error] incompatible return type applying to method-call(void
example.AccountDao.setEntityManager(example.EntityManager))
dao.setEntityManager(PersistenceCreator.createEntityManagerFactory().createEntityManager());
[warning] advice defined in example.AbstractTransaction has not been
applied
[Xlint:adviceDidNotMatch]
I check the syntax and read the example in e.g.
http://books.google.com.tw/books?id=AKuBlJGl7iUC&pg=PA54&lpg=PA54&dq=aspectj+call+args&source=bl&ots=58KGnyCZiN&sig=5gNdHoekFrDXJne3pVe6UO5tiYQ&hl=zh-TW&ei=kNbxSqTEBumgjAfdnp2WAQ&sa=X&oi=book_result&ct=result&resnum=6&ved=0CB0Q6AEwBQ#v=onepage&q=4-2%20capturing%20the%20parameter%20values%20passed%20on%20a%20method%20call&f=false
The way to capture the EntityManager looks correct.
public pointcut(EntityManager manager): call(*
AccountDao.setEntityManager(EntityManger)) && args(manager);
Is there any place I may go wrong? I test to move the .aj files and
compile
.java source. Everthing works fine. I am confused.
I appreciate any suggestion.
Thank you very much.
Mark Cooke-6 wrote:
Hi,
It's been a while since I've used AspectJ in anger but as no-one else
has
replied yet...
I'd say you probably want "args(manager)" instead of "target(manager)"
in
the obtainEntityManager pointcut.
The target of the call will be an AccountDAO, not an EntityManager.
See
http://www.eclipse.org/aspectj/doc/released/progguide/semantics-joinPoints.html
HTH!
Mark.
--- On Wed, 4/11/09, neo anderson <javadeveloper999@xxxxxxxxxxx> wrote:
From: neo anderson <javadeveloper999@xxxxxxxxxxx>
Subject: [aspectj-users] A transaction question
To: aspectj-users@xxxxxxxxxxx
Date: Wednesday, 4 November, 2009, 12:09
I am learning how to modulize transaction using aspectj,
but encounter a
problem that EntityManager I try to capture is always null.
The compiler
issues message saying that the advice can not be applied.
as below:
... advice defined in example.AbstractTransaction has not
been applied
[Xlint:adviceDidNotMatch]
What should I change so that I can capture the
EntityManager while it is
created (whilst calling to
AccountDao.setEntityManager(..))?
Thanks for help.
Main.java
package example;
public class Main{
public static void main(String args[]){
Main m = new Main();
m.process();
}
void process(){
AccountDao dao = new
AccountDao();
dao.setEntityManager(PersistenceCreator.createEntityManagerFactory().createEntityManager());
User u = new
User("1", "Smith");
u.setAddress("123
Test Road, London.");
dao.save(u);
dao.list();
}
}
AccountDao.java
package example;
import java.util.List;
import java.util.ArrayList;
public class AccountDao{
private EntityManager manager;
private static List<User> database
= new ArrayList<User>();
public void
setEntityManager(EntityManager manager){
this.manager =
manager;
}
public void save(User user){
database.add(user);
}
public void list(){
for(User u :
database){
System.out.println(">>>[AccountDao.java]"+u);
}
}
}
User.java
package example;
public class User{
private String id;
private String name;
private String address;
public User(String id, String name){
this.id = id;
this.name = name;
}
public String getId(){
return this.id;
}
public String getName(){
return this.name;
}
public String getAddress(){
return this.address;
}
public void setAddress(String address){
this.address =
address;
}
public String toString(){
return "<User
[id:"+id+"][name:"+name+"][address:"+address+"]>";
}
}
PersistenceCreator.java
package example;
public class PersistenceCreator{
private static EntityManagerFactory
factory;
public static EntityManagerFactory
createEntityManagerFactory(){
if(null == factory)
factory = new EntityManagerFactory();
return factory;
}
}
EntityManagerFactory.java
package example;
public class EntityManagerFactory{
private static EntityManager manager;
public static EntityManager
createEntityManager(){
if(null == manager){
manager = new EntityManager();
}
return manager;
}
}
EntityManager.java
package example;
public class EntityManager{
}
AbstractTransaction.aj
package example;
public abstract aspect AbstractTransaction
percflow(scope()){
private EntityManager manager;
protected abstract pointcut tx();
protected pointcut
obtainEntityManager(EntityManager manager): call(*
example.AccountDao.setEntityManager(EntityManager))
&& target(manager);
protected pointcut scope(): tx()
&& !cflowbelow(tx());
Object around(): scope(){
System.out.println("EntityManager:"+manager);// always null
Object result =
proceed();
return result;
}
EntityManager around(EntityManager
manager): obtainEntityManager(manager)
&& cflow(tx()){
if(null == manager){
manager = proceed(manager);
}
return manager;
}
}
AccountTransaction.aj
package example;
public aspect AccountTransaction extends
AbstractTransaction{
protected pointcut tx(): execution(*
example.Main.process());
}
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--
Simone Gianni CEO Semeru s.r.l. Apache Committer
http://www.simonegianni.it/
