[Zope] Re: [Zope-dev] help me convert from j2ee to zope

[Nitin Borwankar]

Having been forced to use EJB's on a project or three ( Weblogic, 
Websphere, JBoss) and having chosen to use Zope where I have had the 
choice, let me add my 2c worth.

a) Run from EJB's as fast as you can - Zope is the only current 
alternative with any "out of the box"  functionality - actually Zope has 
far far more than any other alternative.  Python is far more 
expressive/productive than Java ( I make my living programming Java ) 
and you can leverage both using  Jython for rapid prototyping using Java 
classes from the Jython prompt.   If you meet an EJB on the road kill it.

b) As far as Session Beans are concerned one difference is that Session 
Beans carry a transactional context that  for the life of the Session
     Session beans are pooled by the container and can be stateful or 
stateless.  If you use stateful session beans, you have to do lots of 
low level  nonsense to manage paged results of SQL queries in J2EE,  
ZSQL methods do all this for you rather nicely.  On the other hand EJB 
containers transparently "passivate"  quiescent sessions and re-activate 
them as needed, maintaining session state.  This is a second order 
optimization that may mean nothing in practice.
ZODB has transactions and you'll need to manage them in ways analogous 
to session beans - you'll have to get "inside" Zope (AFAIK) for that -  
I don't believe  the transaction boundaries are that visible at the 
higher level programming interfaces.  ( I may be wrong here and just 
missing something)

c)  Session beans have a transaction attribute (declarative) that the 
container uses to determine what happens when you call a session bean 
method from another one and one or both are involved in a transaction.  
Should the call result in a new separate transaction, or should the 
called method be included in the callers transaction etc.... are 
determined by these attributes.  Zope doesn't have this level of 
granular control but the reality of J2EE is that the power of this 
metaphor is rarely used in practice as it is too hard to keep all these 
transactions consistent in a large app - so mostly default settings or a 
small subset of the available settings are used > 90% of the time.  In 
Zope the transaction interactions will have to be designed and 
programmatically managed by you rather than declared and then left to 
the container.  Depending on the complexity of your app's transactions 
this may be the largest pain point.

That's my 2c worth - for my 4c worth send me another email :-)

Nitin Borwankar



Paul Winkler wrote:

>On Sat, Jan 24, 2004 at 09:11:29PM -0500, Ryan Boder wrote:
>  
>
>>On Sat, Jan 24, 2004 at 04:28:24PM +0100, Clemens Robbenhaar wrote:
>>    
>>
>>> Usually You should have some persistent object around by the Zope
>>>framework when handling request. If doing an XML-RPC call You are already
>>>talking to some persistent object given to You by the ZPublisher. I am
>>>not sure what is the appropriate equivalent of a session bean in J2EE if
>>>looking at Zope.
>>>      
>>>
>>Not knowing much about Zope, I would assume that a session bean is similar
>>to a non-persistent Zope product, while an entity bean is similar to a
>>persistent Zope product.
>>    
>>
>
>I don't know beans about beans, but from the reading I have done,
>that sounds reasonable.
> 
>  
>
>>>From what I have read about Zope, J2EE and Zope offer very similar services
>>to developers. Straight from the Oreilly EJB book, EJB offers: 
>>concurrency, transactions, persistence, 
>>    
>>
>
>yes, yes, and yes
>
>  
>
>>distributed objects (RPC),
>>    
>>
>
>yes, in a couple of ways. ZEO allows the same zope app to run on
>multiple servers from a single persistence storage.
>Zope also supports XML-RPC. 
>
>  
>
>>naming,
>>    
>>
>
>i don't know what that means.
>
>  
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>>and role based security.
>>    
>>
>
>yes
>
>  
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>>From what I have read Zope offers these same services to products.
>>
>>At first glance it seems like I should be able to just re-implement my EJBs
>>as Zope products and it would work out quite well. Although the Zope
>>developers have said otherwise so I'm not sure.
>>    
>>
>
>What did they say?
>So far you haven't said anything that makes me think Zope is not
>a good fit. 
>
>But a quick translation from EJB to Zope may get
>you something that *works*, but it is likely to be poorly
>designed from a Zope point of view. Before I got my current
>job, the team "translated" a bunch of dynamic content and presentation
>from Weblogic to Zope. It is rather ugly and after 2 years we
>are still stuck with it due to time constraints.
>By comparison, another site which they built from scratch in Zope
>before I was hired, is much nicer to work with.
>
>So, you may want to learn a bit about zope and re-think your architecture 
>before you come up with something maintainable.
> 
>  
>
>>Also I have noticed other similarities (keep in mind I am a Zope novice, so
>>don't take this as fact):
>>JSP == ZPT
>>    
>>
>
>aside from a totally different language design, yes,
>they serve more or less the same purposes.
>
>  
>
>>Servlets == script (python) objects
>>    
>>
>
>hmm, I don't know enough about servlets to judge.
>
>Script (python) is poorly named. They're callable objects,
>kind of like functions, whose code is stored in the zodb and is 
>editable through the web. There are many security restrictions on 
>what Scripts can and cannot do: many modules cannot be imported,
>you cannot define a persistent class in a Script, etc.
>
>Treat them as context-sensitive functions, good for quickly
>implementing small bits of logic.
> 
>  
>
>>I can only see 2 BIG differences in Zope and J2EE...
>>
>>1. Java vs Python (I like Python better) 
>>    
>>
>
>yes, you are one of us :-)
>
>  
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>>My only real reservation is that Zope seems very stuck on making everything
>>a web interface. Personally I don't like web interfaces for most things. I
>>would like to write my programs so that they use the XML-RPC publishing and
>>integrate my client programs with user programs such as eclipse and
>>openoffice.org. For example, one thing I am working on is a requirements
>>management system that stores the data in an application server (hopefully
>>Zope) but the users write their requirements documents in openoffice and
>>openoffice interacts with the app server to store the requirements. I want
>>the main user interface to be openoffice for that, not the web.
>>    
>>
>
>You certainly *can* do that, either using XML-RPC or a "REST" style:
>http://webservices.xml.com/pub/a/ws/2002/02/06/rest.html
>
>  
>