Re: [aspectj-users] Serialization aspect problem

["Eric Bodden" <eric.bodden@xxxxxxxxxxxxxx>]

Hi, Neil.

"f" is a local variable. It's scope is restricted to the advice
declaration. If you want to store the serialized object somewhere you
have to either do this manually (How otherwise would AJ know where to
store f?) or, depending on the context, you may use an around-advice
and return f from that advice to pass it back to the calling context.

Eric

On 19/12/2007, neil loughran <loughran@xxxxxxxxxxxxxxxx> wrote:
> Hi all
>
> I'm trying to figure out what exactly is wrong with my pointcut/advice for a
> serialisation aspect.
>
> The code below is fairly simple but captures the problem I have.  Basically
> I create an object of type Foo and set Foo.x to Foobar. My aspect has two
> advice.. one for capturing instantiation of Foo and the other for capturing
> setX on Foo objects.
>
> On instantiation of Foo, I attempt to load a serialised file (Foo.ser).  If
> it doesn't exist then an exception is thrown but the program carries on as
> usual.  When I setX the second advice serializes the Foo object as file
> Foo.ser.
>
> Therefore when I run the program a second time I expect the Foo.ser file to
> load and the contents loaded to the Foo object.  However, for some reason I
> can't seem to show the loaded value in FooDriver only in the aspect.
> Therefore, I am assuming my first advice is incorrectly written and the
> loaded content is lost outside of the aspect.  I have tried a few different
> varieties of around/after returning advice to no avail.
>
> Can anyone spot the mistake in the first advice... it's driving me nuts!
>
> Many thanks
> Neil Loughran
>
>
>
> import java.io.*;
>
> class FooDriver  {
>     public static void main(String args[])  {
>         Foo f = new Foo();
>         System.out.println("[FooDriver] x = "+f.getX()); // always null!!?
>
>         f.setX("Foobar");
>     }
> }
>
> class Foo  {
>     public String x;
>     public void setX(String _x)  {
>         x = _x;
>     }
>
>     public String getX() {
>                 return x;
>         }
> }
>
> aspect MyAspect  {
>     declare parents: Foo implements Serializable;
>     String filename = "Foo.ser";
>
>     // problematic advice?
>     after(Foo f): this(f) && execution (Foo.new())  {
>         try  {
>             f = (Foo) SerializeObject.load(filename);
>             System.out.println("[MyAspect] x = "+f.getX()); // works fine
> here!
>         }
>
>         catch(Exception e)  {
>             System.out.println("File not found "+ e);
>         }
>     }
>
>     after(Foo f): this(f) && execution(public void Foo.setX(String))  {
>         System.out.println("Setting");
>         try  {
>             SerializeObject.save(f,filename);
>         }
>
>         catch(IOException e)  {
>             System.out.println("File not found "+ e);
>         }
>     }
> }
>
> class SerializeObject  {
>     public static void save(Object obj, String filename) throws IOException
> {
>           System.out.println("Saving file: "+filename);
>         ObjectOutputStream objstream = new ObjectOutputStream(new
> FileOutputStream(filename));
>         objstream.writeObject(obj);
>         objstream.close();
>     }
>
>     public static Object load(String filename) throws Exception  {
>         System.out.println("Loading file: "+filename);
>         ObjectInputStream objstream = new ObjectInputStream(new
> FileInputStream(filename));
>         Object obj = objstream.readObject();
>         objstream.close();
>         return obj;
>     }
> }
>
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-- 
Eric Bodden
Sable Research Group
McGill University, Montréal, Canada