This requires a
little background. For a while now I
have been interested in getting APEX to print directly to a Zebra Printer. Now there are a few printing solutions
available to APEX and I dare not compare to those but in my primary field of
Asset Management we always have a need for direct printing to a very
specialized set of devices; namely Zebra Printers.
A year ago I found
my first solution, and it’s pretty ugly for me and I wasn’t really secure in
publishing it since it has its own issues.
In the last few days I had occasion to revisit the solution and try
again. Time has the benefit of
perspective and so I have another solution as well, yet not the one I was
looking for.
Those who know me,
know that APEX is not my primary skillset.
I’m passionate about it but in my daily life IBM Maximo pays the
bills. Within this system in recent
version came an ability to script some components via Javascript and or Python
(in the form of the Jython library). So
I was looking originally for a way to print these labels from Maximo using this
type of scripting and have mostly found the solution, and might have a final
once IBM finishes troubleshooting a python issue I keep running up against.
To compensate for
this I set up a VM with Oracle XE and created a patch solution using PL/SQL
triggered Python to send ZPL2 code to the printers to get results. Now I dislike using more disparate tech than
required to get the job done but at the time this was it. I came back to this solution and had a minute
to do some thinking and had an idea. Research
showed me that Oracle had a package that did similar work to the Python “socket”
module, which is my current issue in Maximo.
What this knowledge did do is provide a super simple solution to my
complex problem for Oracle and APEX. I
ran with it and today had a stunningly fast printing of my example tags.
This solution takes
a lot from other’s work and twists it to my goal and I will try to give credit
where credit is due.
The first task is to
get the ZPL code for the label to be able to print it. I have always preferred to not write my own
ZPL since it 1500 page reference should speak for itself on how complex it can
get. Instead I use the Zebra Designer and then print the design to a file and then
just grabbing the ZPL code to be used.
The gif below shows that export.
Now that you have the
ZPL, you have to get it to the printer.
PL/SQL-Batch-Python-ZPL Printing
Ugh! Just looking at that string is hard.
From Oracle it is
possible to trigger a python script from pl/sql through DBMS_SCHEDULER. From there the job triggers a .CMD, .BAT, .SH
(for unix) which triggers the python script to do the work. There is less explanation here than there code
I am releasing on gitlab to let you see how it’s done.
Essentially the
package has a set of DBMS_SCHEDULER creation procedures that use some metadata
tables to send parameters to the python script that does the printer
communication. It’s ugly but effective.
PL/SQL-ZPL Printing
This solution came
down to a single line in the python documentation here: https://docs.python.org/3/library/socket.html
“module
provides access to the BSD socket interface”
From there I
searched for BSD Oracle and came to the ‘Pavan’ archive article on
UTL_TCP.
The solution presented
here takes this example directly and twists it slightly to do what I was doing
in the Python script.
At the end of all
this I found a better solution than I originally had and this one really looks
like it can help. If you are interested
grab it, add it to your toolset and get back to work.
As a final note this blog is titled "Precision Guesswork". If what you see here isn't pretty that's why.
Cheers!
Resources:
Labelary
(great place to see ZPL results and to tweak your labels)
Zebra
Designer (demo Licenses can be acquired here)
ZPLII (The
great big book of everything)
python Docs
(socket) (Where this tangent started)
utl_tcp
(credit where it is due)
