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From John Burwell <>
Subject Re: code formatting for enums
Date Fri, 19 Jul 2013 13:33:06 GMT

I expect that renaming an enum value to be a minor change (i.e. once the codebase compiles,
the change is good).  However, i can say I am surprised to learn that such an operation could
break the API and/or corrupt that database.  To my mind, this issue has nothing to do with
developer choice.  Instead, our architecture needs to recognize that an enumerated value may
have multiple representations dependent on the context (e.g. CloudStack HTTP API, AWS API,
UI, code, database, etc), and provide mechanisms to perform transformations between them when
they need to differ.  From a persistence perspective, we need to should be keying off of a
value that is unlikely to change (e.g. an artificial ID).  I would submit that Java enumeration
value names, as code symbols, are subject to an unacceptable level of change to be used for


On Jul 18, 2013, at 8:49 PM, Frank Zhang <> wrote:

> Yes it's brittle.  I assume "law of least astonishment" here means reducing learning
curve of 
> developers and the changes they made should not surprise user. To achieve this the code
> provide very flexibility to developer. However, I am thinking of such kind of flexibility
is really needed, isn't it?
> Currently "Convention over configuration" which sacrifices flexibility for simplicity
is getting more and more
> popular. If we can state clearly to developers on constructing data structure from database
tables to API responses, we are 
> achieving great simplicity and overall coding convention.
> Sometimes, it's better off offering only choice to developer and don't make them think.
Anyway, a [DISCUSS] thread is necessary.
>> -----Original Message-----
>> From: John Burwell []
>> Sent: Thursday, July 18, 2013 4:39 PM
>> To:
>> Subject: Re: code formatting for enums
>> Alex and Frank,
>> In terms of conventions, the APIs exposed Java SDK and many other common
>> APIs following this convention.  Hence, the reason for my suggestion.
>> The notion that changing an enum key can break the API and/or database
>> persistence feels a bit brittle.  In particular, it doesn't conform to the Law of
>> Least Surprise.  It feels like we should have a transformation mechanism from
>> the API endpoint to an enum value, and employ foreign, artificial keys to code
>> tables in schema.  This conversation has expanded a bit, and it seems
>> appropriate to open a new [DISCUSS] thread to delve into it further.  Do y'all
>> agree?
>> Thanks,
>> -John
>> On Jul 18, 2013, at 7:19 PM, Frank Zhang <> wrote:
>>> Those enums cannot be simply considered as internal data structures where
>> code convention applies to, they should be considered in API level.
>>> Most CloudStack API responses retrieve its fields from xxxVO classes
>>> which represent database table. In our example, enum State directly
>>> maps to UserVmResponse. state. Then the most important factor of name
>> convention is user experience where Running is more user friendly than
>> IS_RUNNING or whatever all capitalized sentence splitting by underscore.
>>> And any changes to those existing enum should be thought twice, as it relates
>> to API compatibility.
>>> Though we can introduce some mapping layer between internal enum and
>>> API response, I don't see any benefits if the only reason is to follow some
>> name convention.
>>>> -----Original Message-----
>>>> From: Alex Huang []
>>>> Sent: Thursday, July 18, 2013 3:55 PM
>>>> To:
>>>> Subject: RE: code formatting for enums
>>>> Actually, that's more of a C/C++ coding convention.  (Speaking of
>>>> which, please don't use "I" to start interfaces.)
>>>> I prefer to have enums as follows
>>>> Public class Vm {
>>>> enum State {
>>>> IsRunning,
>>>> Stopped,
>>>> }
>>>> }
>>>> I generally like to write Vm.State.IsRunning  in the code.  It's readable
>> clear.
>>>> As opposed to Vm.State.IS_RUNNING which is a little less readable.
>>>> But the thing I've seen people do is just using IS_RUNNING or
>>>> State.IsRunning which often becomes confusing.  I'm more against that
>>>> then all caps and underscore.
>>>> My $.02.  I will caution that any change to existing enums, we have
>>>> to think about how it maps to the database.  If the VO object stores
>>>> the enum, you'll have to either upgrade the database or add methods
>>>> to the enum so that when storing it, it becomes the same.
>>>> --Alex
>>>>> -----Original Message-----
>>>>> From: John Burwell []
>>>>> Sent: Thursday, July 18, 2013 12:33 PM
>>>>> To:
>>>>> Subject: Re: code formatting for enums
>>>>> All,
>>>>> Another thing I have noticed is that enum values are not capitalized.
>>>>> General coding convention is that enum values are declared in all
>>>>> caps using an underscore to separate words.  I notice that our
>>>>> coding conventions are silent on enumerations.  Any opposition to
>>>>> adding this rule to our coding conventions?
>>>>> Thanks,
>>>>> -John
>>>>> On Jul 17, 2013, at 12:24 PM, Alex Huang <>
>>>>>> That's because the first rule of auto-formatting is do no harm.
>>>>>> The formatter is set not to screw with lines that are already
>>>>>> wrapped
>>>>> assuming the previous developer intended it that way.
>>>>>> --Alex
>>>>>>> -----Original Message-----
>>>>>>> From: Daan Hoogland []
>>>>>>> Sent: Wednesday, July 17, 2013 8:23 AM
>>>>>>> To: dev
>>>>>>> Subject: Re: code formatting for enums
>>>>>>> thanks,
>>>>>>> it doesn't correct back to the one per line format, but at least
>>>>>>> it doesn't garble the enum when right anymore.
>>>>>>> On Wed, Jul 17, 2013 at 4:24 PM, Alex Huang
>>>>>>> <>
>>>>> wrote:
>>>>>>>> Windows->Preferences
>>>>>>>> Java->Formatter
>>>>>>>> Click on Edit in Active Profiles
>>>>>>>> Line Wrapping tab
>>>>>>>> Look for 'enum' declaration->Constants Select Wrap all
>>>>>>>> every element on a new line in the "Line Wrapping policy:"
>>>>>>>> down
>>>>>>>> --Alex
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: Daan Hoogland []
>>>>>>>>> Sent: Wednesday, July 17, 2013 6:22 AM
>>>>>>>>> To: dev
>>>>>>>>> Subject: code formatting for enums
>>>>>>>>> H,
>>>>>>>>> I am working on Networks with the eclipse.epf file loaded.
>>>>>>>>> the enum BroadcastDomainType gets saved as
>>>>>>>>>      Native(null, null), Vlan("vlan", Integer.class),
>>>>>>>>>              String.class), LinkLocal(null, null), Vnet("vnet",
>>>>>>>> Long.class), Storage(
>>>>>>>>>              "storage", Integer.class), Lswitch("lswitch",
>>>>>>>> String.class), Mido(
>>>>>>>>>              "mido", String.class), Pvlan("pvlan",
>>>>>>>>> String.class),
>>>>>>>> UnDecided(
>>>>>>>>>              null, null);
>>>>>>>>> instead of
>>>>>>>>>      Native(null, null),
>>>>>>>>>      Vlan("vlan", Integer.class),
>>>>>>>>>      Vswitch("vs", String.class),
>>>>>>>>>      LinkLocal(null, null),
>>>>>>>>>      Vnet("vnet", Long.class),
>>>>>>>>>      Storage("storage", Integer.class),
>>>>>>>>>      Lswitch("lswitch", String.class),
>>>>>>>>>      Mido("mido", String.class),
>>>>>>>>>      Pvlan("pvlan", String.class),
>>>>>>>>>      UnDecided(null, null);
>>>>>>>>> anybody know how to fix this?
>>>>>>>>> thanks,
>>>>>>>>> Daan

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