Thanks again Jeremias. Your help much appreciated.

I have made the PDFEncryptionJCE class pass itself as source into PDFEventListener.warnRevision3PermissionsIgnored() which gets passed onto the PDFEventProducer.

Yes I am indeed calling PDFEventListener.warnRevision3PermissionsIgnored() from the PDFEncryptionJCE class. The call is originating from the init() method. A bit of debugging and a fresh mind this morning revealed that getDocumentSafely() is throwing an exception as the returned document is null. (That was getting swallowed up and the InvocationTargetException thrown instead that I got at the end of Friday.) So I think your last paragraph is applicable in that PDFEncryptionManager will need to be modified to set the PDF immediately as you say. So my next step is to work out how I should do that...

Thanks!

-Mike

On 14/05/11 10:42, Jeremias Maerki wrote:
On 13.05.2011 17:06:56 Michael Rubin wrote:
Thanks for your reply. I have now added the getter and setter to
PDFDocument as shown below and added 'this.pdfDoc.setEventListener(new
PDFLibraryEventAdapter(getUserAgent().getEventBroadcaster());' to
PDFDocumentHandler.startDocument() (last line inside the try block). Now
I can get the listener from the PDFEncryptionJCE class. However what do
I do with it?
You call your PDFEventListener.warnRevision3PermissionsIgnored() method.

And how does this relate to the producer class and the
EventBroadcaster that I am trying to get hold of?
It doesn't. That's part of the decoupling. The PDFEncryptionJCE should
know nothing of the EventProducer or EventBroadcaster.

Maybe the attached UML helps a bit (I don't usually do UML so I'm not
sure I've made any mistakes).

In your first reply you said to create the Listener and Producer
interfaces. Based on the FontEvent* classes, both of these had an event
definition for their events. But in the latest reply you are saying not
to put my event in the new PDFEventListener? That would make it an empty
interface then if I understand right. So what would its purpose be? I
can't seem to do anything with it.
Sorry for the confusion here. I didn't remember that there was already
an EventProducer in org.apache.fop.render.pdf. So adding a new
EventProducer doesn't make much sense. Instead your
warnRevision3PermissionsIgnored() should be added to the existing one.
No new EventProducer is necessary (and I didn't notice that at first).

Following discussion with a colleague (Vincent) I left the listener
method in (but without the source) and made the call to that to kick off
the event. However now I get an InvocationTargetException when I try to
get the PDF Doc in order to invoke the listener event method. Looking at
the stack trace it happens when I call the
PDFDocument.getDocumentSafely() method. It seems when debugging to be
PDFEncryptionManager.newInstance() where the error is occurring, the 3rd
line calling makeMethod.invoke(...). (I attempted to run the build ant
script and then refresh eclipse but this didn't make any difference.)
I can't help much with that InvocationTargetException. Maybe if you
posted a patch so I could reproduce it....

I will continue with this on Monday. Any further pointers in the
meantime very much appreciated.

There are two questions that come from my colleague:

1. What is the source object for? And do we need it referenced in the
Listener? Or just the producer?
My original idea was that this object gives the event handler a chance
to intercept and modify the object that is the event origin. In most
cases, it will certainly be ignored but someone might find it handy. And
to have it in the producer means you also have to have it in the
PDFEventListener. See also java.util.EventObject from which
org.apache.fop.events.Event is derived.

2. Why should we get the PDFDocument object from the Encryption class?
It's a PDFObject, right? So it should already have the PDFDocument. That
makes access to the PDFEventListener easy.

Should the listener not be passed into the Encryption class via its
constructor rather than having to go fetch the listener?
Both are valid ways but since I expect the PDFDocument to already be set,
I see no point in giving more information that can otherwise be easily
accessed. Well, it could be that your event happens before the
PDFDocument is set on that object (see PDFDocument.setEncryption()). In
that case PDFEncryptionManager might have to be changed to pass in the
PDFDocument immediately. Or you pass in the PDFEventListener, although I
find the former more useful and flexible.

Thanks!

-Mike


On 12/05/11 21:29, Jeremias Maerki wrote:
On 12.05.2011 10:44:41 Michael Rubin wrote:
Thanks a lot for your response Jeremias. I have now done the following:

- Added 'void warnRevision3PermissionsIgnored(Object source);' (and its 
javadoc) to PDFEventProducer in the org.apache.fop.render.pdf package and added 
a corresponding entry to the xml. Removed the 
org.apache.fop.pdf.PDFEventProducer class and xml.
- Created org.apache.fop.pdf.PDFEventListener interface containing just 'void 
warnRevision3PermissionsIgnored(Object source);'.
- Created PDFLibraryEventAdaptor in the org.apache.fop.render.pdf package that 
extends the PDFEventListener. (Currently just contains my new event. Should I 
also add the existing 2 render.pdf events to this class?)
Or do it the other way around: add your new event to PDFEventProcuder.
Doesn't make sense to have two.
    I can also see how to obtain the PDFDocument object from the
PDFEncryptionJCE class via the getDocumentSafely() method. But I am not sure 
how to get the event broadcaster from that object. How is this done?
public class PDFDocument {

[..]

      private PDFEventListener listener;

[..]

      public void setListener(PDFEventListener listener) {
          this.listener = listener;
      }

      PDFEventListener getListener() {
          return this.listener;
      }
[..]

That's the simples way and should probably be sufficient. If we wanted
to get fancy, we could handle a List<PDFEventListener>.

In PDFDocumentHandler.startDocument():
this.pdfDoc.setEventListener(new 
PDFLibraryEventAdapter(getUserAgent().getEventBroadcaster());

So, the PDFDocument doesn't actually get an EventBroadcaster.
PDFDocument calls the PDFLibraryEventAdapter and that one in turn calls
the EventBroadcaster. Nicely decoupled.


Thanks!

-Mike


On 11/05/11 19:46, Jeremias Maerki wrote:
Hi Michael

Creating a new EventBroadcaster is obviously wrong. The idea is that the
user can get events for each FOP rendering run separately (unlike
logging where concurrent runs get mixed up). So you have to get hold of
that EventBroadcaster applicable to the current rendering run. Obviously,
you don't have access to the FOUserAgent in the PDF library. That is
intentional because the PDF library should remain reasonably independent
of as much FOP code as possible for the case that we ever factor it out
into a separate component/module or move it to XML Graphics Commons.

My suggestion is to follow a similar path as done in
org.apache.fop.fonts: Create an interface for the events coming out of
the PDF library (see FontEventListener). Let's call it PDFEventListener
or something like that and put it in the org.apache.fop.pdf package.
Then move your PDFEventProducer (corresponds to FontEventProducer) into
org.apache.fop.render.pdf as this package makes the glue between FOP and
PDF output. Then create a PDFLibraryEventAdapter (implements PDFEventListener)
in the org.apache.fop.render.pdf package (corresponds to
FontEventAdapter). The PDFLibraryEventAdapter will get the
EventBroadcaster from the PDFDocumentHandler which is responsible for
instantiating the PDFDocument and PDFLibraryEventAdapter. The adapter is
then added as listener to a List<PDFEventListener>    that you can add to
PDFDocument. From PDFEncryptionJCE you should have access to the
PDFDocument via the getDocumentSafely() method. That nicely decouples
FOP's event subsystem from the PDF library.

HTH

On 11.05.2011 15:47:49 Michael Rubin wrote:
?Hello there. I have been busy implementing 128 bit PDF encryption for FOP. I 
have already got it working successfully but one issue remains that I have a 
question about.

In the org.apache.fop.pdf.PDFEncriptionJCE.init() method there is one place where I want 
to broadcast an event message. I looked 
athttp://xmlgraphics.apache.org/fop/trunk/events.html  to learn about events. However it 
just shows "EventBroadcaster broadcaster = [get it from somewhere];" and 
doesn't show how I should be getting the broadcaster. After looking in the code in the 
AFP package for existing examples I put together the following which seems to work on 
testing:

FopFactory fopFactory = FopFactory.newInstance();
FOUserAgent agent = fopFactory.newFOUserAgent();
EventBroadcaster eventBroadcaster = agent.getEventBroadcaster();
PDFEventProducer eventProducer = 
PDFEventProducer.Provider.get(eventBroadcaster);
eventProducer.warnRevision3PermissionsIgnored(this);

This creates a new FopFactory, from which I create a new FOUserAgent, from 
which I can get the event broadcaster to supply to my event producer. (I had to 
create a PDFEventProducer which extends EventProducer. Plus 
PDFEventProducer.xml which contains the message mapping.)

In this case the EventBroadcaster will be created new every time so I am not 
sure existing listeners will pick up. So is there a recommended way that I can 
get an existing event broadcaster to use? Or is the above way the correct way 
to do it after all?

Version of FOP is v1.0. Platform is Ubuntu Linux, running from within the 
Eclipse IDE.

Thanks!

-Mike





Michael Rubin
Developer

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