[Zope] Experiment: Pyjamas with Zope

20 Dec 2008

      So, I have a need to put together a more elaborate web page.  Lots of 
pop-up dialog boxes and dynamically-updated choice lists.  How to do that?

I take a look at Pyjamas http://pyjs.org. Pretty cool.

Here's the theory.  Write fancy application web page in python using the 
Pyjamas/GWT API, then "compile" it to javascript.  Serve it through 
zope, which will handle auth/auth.  Client-server communication flows 
through json-rpc calls.  What could possibly go wrong?

First-off, just a simple test-of-concept.  Edit the JSONRPCExample.py 
file in the examples/jsonrpc folder that came with pyjamas.

I'll locate the jsonrpc service in zope's containment root, so I change 
the uri in EchoServicePython from "/services/EchoService.py" to "/". 
That's all I need to change.  Compile it using the handy "build.sh" 
that's in the same folder.  Look in the "output" folder and see what we got.

Wow. a bunch of files.

JSONRPCExample.IE6.cache.html
Mozilla.cache.html
OldMoz.cache.html
Opera.cache.html
Safari.cache.html
JSONRPCExample.html
JSONRPCExample.nocache.html
corner_dialog_bottomleft.png
corner_dialog_bottomleft_black.png
corner_dialog_bottomright.png
corner_dialog_bottomright_black.png
corner_dialog_edge.png
corner_dialog_edge_black.png
corner_dialog_topleft.png
corner_dialog_topleft_black.png
corner_dialog_topright.png
corner_dialog_topright_black.png
history.html
pygwt.js
tree_closed.gif
tree_open.gif
tree_white.gif

I'm lazy, so instead of doing a bunch of resource or view directives in 
ZCML, I let my paste.ini do the handling.

[app:pyjs1]
use=egg:Paste#static
document_root=/home/jwashin/projects/pyjamas/pyjamas-0.4/examples/jsonrpc/output

then, I link that in with the composite app.

[composite:Paste.Main]
use = egg:Paste#urlmap
/ = zope
/images = images
/pyjs1 = pyjs1

Now, to get to JSONRPCExample.html, I need to go to 
http://website/pyjs1/JSONRPCExample.html

But first, I need to actually handle the json-rpc requests in zope.

Make a servicetest.py.  Almost exactly similar to EchoService.py in the 
output/services folder.

from zif.jsonserver.jsonrpc import MethodPublisher
class Services(MethodPublisher):
     def echo(self, msg):
         return msg
     def reverse(self, msg):
         return msg[::-1]
     def uppercase(self, msg):
         return msg.upper()
     def lowercase(self, msg):
         return msg.lower()

Now, a ZCML incantation.

<jsonrpc:view
     for="zope.app.folder.interfaces.IRootFolder"
     permission="zope.Public"
     methods="echo reverse uppercase lowercase"
     class = ".servicetest.Services"
     />

Start zope, and go to http://website/pyjs1/JSONRPCExample.html

Nice page.  Click the "Send to Python Service" button.

Server Error or Invalid Response: ERROR 0 - Server Error or Invalid Response

Damn.

Pull up tcpwatch and see what we are getting.  Aha.  pyjamas app is 
sending jsonrpc with a content-type of 
application/x-www-form-urlencoded, so zope is not handing it off to 
zif.jsonserver for handling.

Fix pyjamas or let zif.jsonserver handle this content-type?

In zif.jsonserver's configure.zcml, in the "publisher" directive, add 
application/x-www-form-urlencoded to mimetypes.

Restart zope. Go to http://website/pyjs1/JSONRPCExample.html

It works.

Change permissions in the jsonrpc:view directive.  Restart zope.

Go to the page.  Page loads.  Push the button, and I get a Basic HTTP 
Authentication dialog.  Nice.

Overall Results:  So far, so good. :)

- Jim Washington