Hope this helps,
Simone

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/

On Nov 2, 2009, at 5:53 PM, Andy Clement wrote:

but that adds in a declare statement

Just to say, if you annotate the ITD, that will be on the introduced
target method - you don't need an additional 'declare @method'.

From a Roo project:

@javax.persistence.Id
@javax .persistence .GeneratedValue(strategy=javax.persistence.GenerationType.AUTO)
@javax.persistence.Column(name="id")
private java.lang.Long Pet.id;

cheers,
Andy

2009/11/2 Dave Whittaker <dave@xxxxxxxxxx>:

Just thought I'd throw in here with a case where I've ran into problems with
this... JPA. If you have common fields you want to inject into an entity
you might try to do something like

private String CommonInterface.commonField

And expect at runtime that will result in a db column named common_field, or
whatever else your naming strategy comes up with. Sure you could use the
@Column annotation and explicitly give it a name, but that adds in a declare
statement and it is definitely a bit confusing when you first run across the
issue. JPA is not the only framework to do this type of reflection these
days, Seam's @In injection is another one that tries to determine a value
based on the name of the field.

Of course i imagine this was done to avoid naming collisions when you
receive fields from multiple ITDs and I'm not sure I see a better solution.

On Nov 2, 2009, at 5:03 PM, Andrew Eisenberg wrote:

Hi,

The ajc$interField$mypack_mysubpack_MyAspect$id is internal and not
expected to be directly referenced in the source code. It is only
needed for the byte code (i.e., you should not be concerned with it).
All you need to know is that the declaration declares an Integer field
'id' on MyClass that is private to the aspect (ie- it is not
accessible anywhere outside the aspect).

Unless you require knowledge about the byte code, the byte code name
should not be of concern to you. However, if you do require knowledge
about the byte code, please explain what that is and perhaps we can
help you.

--a

On Mon, Nov 2, 2009 at 2:45 PM, db <dbconrado@xxxxxxxxx> wrote:

Hi All,

I have an intertype declaration like this:

private Integer MyClass.id;

but, when it was compiled/weaved, this attribute receive the name:
ajc$interField$mypack_mysubpack_MyAspect$id.
I want MyClass receive an id attribute and not a ajc$...$id attribute.
How to do it?

Thanks!

PS: Sorry for my poor English. It isn't my native language :).

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