[ovirt-devel] Custom Properties code duplication

Mon May 5 16:08:23 UTC 2014

Hey guys (and gals),

A few patches are up for review starting at:
http://gerrit.ovirt.org/#/c/27383

In total, about 250 lines of code removed, hopefully not at the cost of
regression. I put down some reviewers as I saw fit, but everyone can
feel free to add themselves. Summary of what was done compared to the
original plan:

1. Removed said dependencies, except for DeviceCustomPropertiesUtils
that was using the capture groups features of Pattern, and thus remained
in the utils project.

2. Done.

3. Done.

4. Almost didn't touch this, it seems to involve a lot of moving parts.

Yours, Lior.

On 30/04/14 18:01, Vojtech Szocs wrote:
> Hi Lior, please find my comments inline.
> 
> 
> ----- Original Message -----
>> From: "Yair Zaslavsky" <yzaslavs at redhat.com>
>> To: "Lior Vernia" <lvernia at redhat.com>
>> Cc: devel at ovirt.org
>> Sent: Wednesday, April 30, 2014 3:28:06 PM
>> Subject: Re: [ovirt-devel] Custom Properties code duplication
>>
>>
>>
>> ----- Original Message -----
>>> From: "Lior Vernia" <lvernia at redhat.com>
>>> To: devel at ovirt.org
>>> Sent: Wednesday, April 30, 2014 3:52:16 PM
>>> Subject: [ovirt-devel] Custom Properties code duplication
>>>
>>> Hello,
>>>
>>> While adding network custom properties towards oVirt 3.5, I got to take
>>> a good look at the custom properties code in the backend and frontend.
>>> It seems to me like there's a lot of code duplication, and I would like
>>> to suggest the following refactoring:
>>>
>>> 1. Remove dependencies on Pattern/Matcher and ApacheCommons methods from
>>> *CustomPropertiesUtils.java, to make them compilable with GWT, and move
>>> these utilities to the common package. The usage of the said methods is
>>> minimal and could easily be replaced with String methods, etc.
> 
> +1
> 
>>
>>
>> In general I am in favor, but how are you going to perform the regex
>> validation of values?
>> for example , with vm custom properties, you have - sap_agent that can be
>> either true or false.
>> So you need to validate both at the client and the engine, right?
> 
> Lior mentioned above the possibility of using String methods, I assume
> by this he means java.lang.String.matches(String) and similar methods.
> 
> During GWT compilation, JRE standard String implementation is replaced
> by emulated (GWT-friendly) String implementation, which implements
> methods like matches(String) using JavaScript RegExp object. You can
> find this emulated implementation here:
> 
>   gwt-user-{version}-sources.jar/com/google/gwt/emul/java/lang/String.java
> 
> Another alternative is to use GWT's built-in regex support through
> com.google.gwt.regexp.shared.RegExp class. GWT's RegExp class has two
> implementations, default one using JRE Pattern/Matcher, emulated one
> using JavaScript RegExp object. The advantage is (mostly) consistent
> regex support on both client and server, the disadvantage is server's
> dependency on GWT JAR. (I don't think we want this.)
> 
> For simple regex matches, I'd suggest to simply go with String approach.
> 
> For complex regex matches, we can use JRE Pattern/Matcher on server,
> and emulate given implementation using GWT RegExp on client.
> 
> Note that there are (slight) differences between JRE's Pattern/Matcher
> and JavaScript's RegExp object syntax/behavior. Check GWT RegExp class
> Javadoc to see details (for simple cases, it's not a big deal, though).
> 
>>
>>>
>>> 2. Modify KeyValueModel to delegate to the common utilities instead of
>>> duplicating code, e.g. for validation.
> 
> +1
> 
> I see that KeyValueModel uses RegexValidation class that delegates to
> compat's Regex class. Just like above, default Regex class utilizes
> JRE Pattern/Matcher but client uses emuluated implementation:
> 
>   gwt-extension/src/main/java/org/ovirt/engine/ui/uioverrides/org/ovirt/engine/core/compat/Regex.java
> 
> and this emulated implementation uses GWT RegExp class.
> 
>>>
>>> 3. Move some validation, which is relevant to all custom properties
>>> (e.g. duplicate keys), from specific utils (e.g. VmPropertiesUtils) up
>>> to the shared CustomPropertiesUtils.
> 
> +1
> 
>>>
>>> 4. Optionally change the implementation of custom properties members in
>>> entities (e.g. VM) from String to Map<String, String>, which would
>>> obviate the need for different conversion methods between String/Map -
>>> (de)serialization would only be required in DB interaction.
> 
> +1
> 
>>
>> 3,4 Agreed - good points.
>>
>>>
>>> The main argument against this would be that the frontend is to be moved
>>> over the REST, and might not be written in Java much longer anyway.
> 
> :) I think there's a misunderstanding regarding our move to REST API.
> 
> The plan is to have JavaScript SDK for working with REST API (so that
> any JavaScript client can work with Engine, be it web application in
> browser, server application on node.js etc.), and for our GWT-based UI,
> generate GWT/Java overlay code that delegates (via JSNI) to JavaScript.
> 
> This is similar approach to projects like SmartGWT which are simply
> overlays (wrappers) to native JavaScript library (like SmartClient).
> 
> So the frontend code will still be GWT/Java, it will just consume
> JavaScript SDK via the above mentioned overlay code for seamless
> SDK user experience in GWT/Java context.
> 
> We may think of implementing parts of UI in JavaScript, though.
> For example, utilizing UI plugins to implement different UI parts
> as plugins, possibly by using JavaScript directly (which could use
> JavaScript SDK). However, this is something different and requires
> deeper thought.
> 
>>>
>>> However, to my understanding, there's some time until these changes take
>>> effect. And even if the frontend is to be written in JavaScript, at
>>> least initially the existing frontend code will have to still be used
>>> somehow (e.g. auto-translated to JavaScript). That is to say, this
>>> refactoring might still be beneficial for the not-so-short term.
> 
> I think this refactoring will be beneficial also in long term :)
> 
>>
>> I agree with you here.
>>
>>
>>
>>
>>>
>>> Before going through with this, I wanted to ask for your thoughts and to
>>> hear any specific objections to the proposed changes.
>>>
>>> Yours, Lior.
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>>>
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