August 2000 - Zope-Dev

permissions/authorization on non ZClass/product objects
by Karl Anderson 03 Aug '00

03 Aug '00

I'm having trouble with permissions and Python class instances that aren't part of the Zope permission mechanism. I'm creating plain Python class instances in the Python baseclass of a ZClass, and storing them in a list on the baseclass. The baseclass instantiates these instances and appends them to its list. The class is defined in the baseclass .py file. A method on the baseclass returns this list of instances, and I'm iterating over them in DTML and looking at their attributes - or trying to. I get an authorization prompt, which always gives me an auth error, even though the user can look at the ZClass that's returning the instances. I'm able to get around this by registering the plain Python class as a base class, subclassing them with a ZClass, and instantiating ZClass instances instead of baseclass instances. It seems like overkill, though (and I always thought that instantiating ZClasses in python was confusing). I don't need to expose methods or restrict access, just open the attributes to be used as DTML variables. Are there ways to do this without making full-fledged ZClasses out of my classes? Are there guidelines in general for using non-Zopish subobjects that get used by the publishing process? -- Karl Anderson kra(a)monkey.org http://www.pobox.com/~kra/

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Abstract ZClasses
by Dieter Maurer 02 Aug '00

02 Aug '00

I would find an abstract ZClass (or Meta ZClass) concept very nice (and useful). I would like to use it, e.g., for a general hieararchical view on relational databases. The view allows browsing (via the tree tag) and selection of one or more items. Most can be implemented independantly of the specific hierarchical relation inside the database. A few parameters and the SQL method are dependant on the database tables. A few others are still more specific, e.g. tree display style and single/multiple selection. Thus, I would prefer the following structure: HV: generic Hierarchical View -- abstract defines the interface and a minimal set of required properties and methods implements most of the functions HV_T1, HV_T2, ...: Hierarchical View specialized for a specific hierarchical relation this (standard) ZClasses define the SQL method and instantiate some parameters of HV i_T1_1, i_T2_2, ...: Instances of HV_T1 more specializations (parameters, presentation methods). Most can be done with the current ZClass architecture: the intermediate ZClasses HV_T1, ... are all derived from ZClass HV. The instances are instances of the intermediate ZClasses. There are 2 exceptions: * HV_T1 cannot specialize properties of HV. They can be specialized in the instances of HV_T1, but it would be nice, if it could be done in the class, if all/most instances share the same value. Workaround: do it in the HV_T1 constructor. * Instances can override property values but not methods. Trying to add a method overriding a default class behaviour results in an "Id already exists" error. Workaround: give the overriding method a different name and let the default method look whether something overriding exists. What do you think about abstract (or Meta) ZClasses? Dieter

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MethodGeddon
by Chris Withers 02 Aug '00

02 Aug '00

http://www.zope.org/Wikis/zope-dev/MethodGeddon Just been reading about this and I was wondering how is coming along... Is it in the fishbowl under another name or should it be in the fishbowl? Shane, would the argument list be a management tab for methods? That sounds cool to me :-) I reckon 'self' should always be the equivalent of the python 'self' or not exist to avoid confusion. I guess that means it wouldn't get used much since it would be the actual method-object (and I thought that was an oxymoron ;-) but with the possibility opf things like __render__ and __call__, who knows... The argument list would be great, 'cos you could then be able to specify additional arguments of type 'binding' which might be any of the following from you list: (select by dropdown? ;-) > Bind to the object containing a method, > Bind to the object that acquired a method, and possibly > Bind to the object containing the method in the context of the object that acquired the method, and maybe even > When a method is defined in a ZClass, bind to the instance in such a way that attribute lookup is performed in the baseclasses of the class defining the method (aka bind to "super"). So you could get to any or all of those as you need in your method. Of course, new users wouldn't have to worry about this until they needed to do something that used it. The other option would be to have these automatically bound to certain names (like _ is now) but perhaps that would be more confusing? Thoughts and comments would be great :-) cheers, Chris

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topics for products
by ethan mindlace fremen 01 Aug '00

01 Aug '00

Zopatistas! The product page is now topic-ized. Please check your product to ensure that it's in the categories you want it to be in. A product can have more than one topic. If there is any flamage/suggestions regarding chosen topics, please send to zope-web(a)zope.org -- ethan mindlace fremen Zopatista Community Liason Abnegate I!

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[Zope] App isolation
by Jacques Exelrud 01 Aug '00

01 Aug '00

Not sure if this list is the best place to put such question but here it is... I need to develop what would be a product if only Zope was the target. As it´s not I was thinking what could I do to not need to build such app twice: I came to 2 options both involving building a server of some kind and using Python to connect to this server. 1st Build the app as a COM server (the target OS is Windows) and using Python support build an interface to this COM server as a Zope product 2nd Build the app as a XMLRPC server and using Python support build an interface to this XMLRPC server The second options is better because I´m not attached to any platform but, as I said, that´s not an issue right now. Good options would be having a JVM running "inside" Zope so that jave objects could be accessed by it or SOAP Zope support beeing ready... Any sugestions on any of those or a 3rd option ? Thanks in advance, Jacques

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RE: [Zope-dev] [Zope] App isolation
by Brian Lloyd 01 Aug '00

01 Aug '00

> I´m waiting for Zope´s support to SOAP but while it´s not > there I´m > tetsing a COM object that will handle the SOAP communication > and will be > calling this component using win32com moudle with Python. In > fact that´s > what I´m testing right now but untill now this COM object is > not building > the right SOAP message and based on that it´s not working. > Do you know when we are supposed to have SOAP support on Zope ? While it is something that we definitely want to see, SOAP support is currently not actively being worked on so I can't give any kind of timeframe. It is really a resource issue - the best way to give this priority is for those interested and motivated is to get together and start this as a project on dev.zope.org. I'll be happy to help out in any way I can as well. Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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ZOracle LOB Questions
by Alexander Schad 01 Aug '00

01 Aug '00

Hello! i have Oracle 8.1.6 ZOracleDA 2.2 installed with Zope 2.1.6 on a red hat linux machine. i have an oracle table with one column containing blobs. Now i have the following problems: 1. How can i retrieve data from that table in zope or in python (syntax) ? 2. How can i insert data to that table ? i need the zope syntax something like: insert into blob_table values ('<dtml-var image>') ??? or the python syntax i have written a little script: import DCOracle, sys, os, DCOracle.dbi dbc = DCOracle.Connect('mozdb_dba/mozdb_dba') cur = dbc.cursor() fn = open('test_img.jpg','rb') data = fn.read() fn.close() param = DCOracle.dbi.dbiRaw(data) cur.execute('select blobcol from blobtable') dat = cur.fetchone() cur.close() dbc.close() print dat when i try to execute it i get the following error: Traceback (innermost last): File "blobtest.py", line 12, in ? dat = cur.fetchone() File "DCOracle/ociCurs.py", line 339, in fetchone self._error() File "DCOracle/ociCurs.py", line 109, in _error raise error, (rc, oci_.OracleErrorMessage(self._c.lda, rc)) oci.error: (24813, 'ORA-24813: cannot send or receive an unsupported LOB\012') 3. Is there a way to call a stored procedure or function that actually return values ? i succeeded in retrieving one particular value out of a table but when i try a function like : select * from some_table i fail... 4. Changes.txt: Z Oracle DA Releases 2.2.0 Added a small feature that allows you to access LOBs in the Oracle database. To do this, you must have your maximum number of results set to '1'. Otherwise, it won't work. i don't know what this is referring to. where should i make this change? Ciao, Alex -------------------------------------------------------------------------- Alexander G. Schad (Programmer) beehive elektronische medien gmbh -------------------------------------------------------------------------- mailto:ags@beehive.de mailto:service@beehive.de http://www.beehive.de fon: (+49 30) 84 78 20 fax: (+49 30) 84 78 22 99

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MySQL Transaction Support
by Monty Taylor 01 Aug '00

01 Aug '00

We were talking about this a while back and I believe came to a consensus about having two different ZMySQL adapters, one for transactions, one for not. However, since each table can have a different type, this might not bode too well for someone that needs a connection to draw from one table with BDB and one without. If you look at the output of the mysqldump utility, using --opt, it shows both server version and table type. I think we should be able to add a function to _mysql.c that would expose that information on a per-table basis. We could then make the call as to whether the sever supports transactions or not. A question would be, what should the commit/rollback mechanism decide to do when the transaction deals with tables of both types. I would suggest a default behavior of not allowing transactions in a mixed type situation, with a way to set an overriding option to allow the rollbackable table to be rolled back and leave the other as is. Hopefully the application designed wouldn't cause that kind of insanity, but hey, if they want to, they'll find a way. Does anyone have any thoughts on this approach? Baring any blaring negative comments, I'll start working on knocking up something like this. Monty

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Ids starting with _
by Chris Withers 01 Aug '00

01 Aug '00

Dieter Maurer wrote: > > I wonder why starting folders with _ is so bad in Zope? > In the time, when everything was allowed what was not explicitely > forbidden, an easy way was necessary to forbid access. Jim > (and, therefore, Zope) used: > > anything starting with "_" is private: no DTML access, no Web access. > > Now, with the change to a security policy "Everything is > forbidden when not explicitely allowed", the need for > such a rule based on naming dwindles. Maybe, it will disappear > sometime in the future. Maybe this is something for dev.zope.org? cheers, Chris

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RE: [Zope-dev] Using other than NullResource to handle HTTP PUT
by Brian Lloyd 01 Aug '00

01 Aug '00

> I'm developing, in python, some classes whose instances to be > published by Zope, one of which is folder-like, i.e. is can contain > instances. I want HTTP PUT requests which will create new object > instances within instances of this folder-like class to be handled by > a PUT function I define. I cannot identify the "right" way to do > this, or at least a way which doesn't involve hacking the standard > Zope code to have my PUT function handle the operation. > > The normal behaviour of Zope appears to be to create an instance of > the NullResource class and call the PUT function on that. This then > proceeds to create a DTMLDocument, Image or File instance which is > not what I need to happen; I want to have instances of one of my own > classes created instead. Hi Richard, If you look at the OFS.ObjectManager.ObjectManager class, you'll see that it overrides __getitem__ and returns a NullResource object if the requested key is not found as an actual subobject. The reason for that is that for the purposes of WebDAV (and plain old HTTP 1.1 PUT) we want traversal to a non-existant URL to retrieve an object that can understand a PUT command. To achieve this, we want to create a NullResource "on the fly" and return it if a non-existant subobject is requested. Note that we *only want this to happen during URL traversal*. To make this happen, we take advantage of the way that the traversal machinery looks for subobject. Lets say you have a URL /products/spam and that the publisher has already found the 'products' object (which is a Folder-like object). What the publisher does with the 'products' object to try to find the 'spam' subobject is: o see if the object has an '__bobo_traverse__' method, and if so, call it passing the REQUEST and the name it is trying to look up. The value returned from this method will be used as the subobject. This gives container-like objects a hook to return 'on the fly' objects. o if no __bobo_traverse__, try to do a getattr() on the object with the given name. If this succeeds, the result is used as the subobject. o if getattr() fails, try to do a getitem (object['name']) to get the subobject. This gives container-like objects another opportunity to provide a hook by implementing an __getitem__ method to perform the name lookup and return the right thing. The default implementation of __getitem__ in ObjectManager provides HTTP PUT and DAV support for containers: def __getitem__(self, key): v=self._getOb(key, None) if v is not None: return v if hasattr(self, 'REQUEST'): request=self.REQUEST method=request.get('REQUEST_METHOD', 'GET') if not method in ('GET', 'POST'): return NullResource(self, key, request).__of__(self) raise KeyError, key So - the short story is that the way you should go about implementing a custom handler for your collections is to override __getitem__ with your own custom handler. Your handler probably could just subclass NullResource in fact, overriding the PUT method to do what you want. > btw am I alone in struggling to understand the python classes > underlying Zope's operation and how these classes work/ineract? I've > read a lot of source code but still feel I have only the vaguest > grasp of the theory of operation of the whole thing. Ho hum. You are certainly not alone :^) Any large codebase really needs a "10,000 foot view" map to help people understand the individual bumps in the terrain in context at ground level. That is something that we are currently missing with Zope (though there are "partial maps" around in the form of UML models of certain parts like ZODB). That is something I'd like to work toward on dev.zope.org in the future. Hope this helps! Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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