Info: How is Dao doing the update?

[Vijay Venkatachalam <Vi...@citrix.com>]

Hi,

Today I came one step close to understand the way GenericDao has implemented
the update in DB.  I thought this understanding might be of use to someone who is new
to CloudStack like myself. Please read on

Observation:
                Changes  in a setter in VO would never reflect in the DB.
public setName(String name) {
# it gets stored with the contents of argument "name" not "this.name"
                this.name  = "Name: " + name;
}
Reason:
                The setter functions of a VO are intercepted and UpdateBuilder.java stores the
argument in a private list "_changes" and this is what is used to update the DB
at a later stage and *not* the object present in the member variable "this.name".

Suggestion/Fix:
                In my case I had a function like the following
                private String counterParameters;
setCounterParameters(Map map) {
                //loop through all the entry sets
                // concatenate them as a tempString  store it like the following
this.counterParameters = tempString;
}

I changed it as

# Plain vanilla function that is intercepted for update
setCounterParameters(String counterParmaaters) {
                this.counterParameters = counterParameters;
}
#custom setter which changes values
setCounterParametersForUpdate(Map map)
{
                // loop through all the entry sets
                // concatenate them as a tempString
setCounterParameters(tempString);
}

Any other Recommendation?:
                Is there a better way to get the Fix done?


Thanks,
Vijay V.

RE: Info: How is Dao doing the update?

[Alex Huang <Al...@citrix.com>]

> -----Original Message-----
> From: Vijay Venkatachalam [mailto:Vijay.Venkatachalam@citrix.com]
> Sent: Monday, September 03, 2012 4:12 AM
> To: cloudstack-dev@incubator.apache.org
> Subject: Info: How is Dao doing the update?
> 
> Hi,
> 
> Today I came one step close to understand the way GenericDao has
> implemented the update in DB.  I thought this understanding might be of use
> to someone who is new to CloudStack like myself. Please read on
> 
> Observation:
>                 Changes  in a setter in VO would never reflect in the DB.
> public setName(String name) {
> # it gets stored with the contents of argument "name" not "this.name"
>                 this.name  = "Name: " + name; }
> Reason:
>                 The setter functions of a VO are intercepted and UpdateBuilder.java
> stores the argument in a private list "_changes" and this is what is used to
> update the DB at a later stage and *not* the object present in the member
> variable "this.name".
> 
> Suggestion/Fix:
>                 In my case I had a function like the following
>                 private String counterParameters; setCounterParameters(Map map)
> {
>                 //loop through all the entry sets
>                 // concatenate them as a tempString  store it like the following
> this.counterParameters = tempString; }
> 
> I changed it as
> 
> # Plain vanilla function that is intercepted for update
> setCounterParameters(String counterParmaaters) {
>                 this.counterParameters = counterParameters; } #custom setter
> which changes values setCounterParametersForUpdate(Map map) {
>                 // loop through all the entry sets
>                 // concatenate them as a tempString
> setCounterParameters(tempString); }
> 
> Any other Recommendation?:
>                 Is there a better way to get the Fix done?
> 

Vijay,

GenericDao was developed specifically to handle only entity mapping but not relational mapping.  The idea was that relational mapping is much easier to get wrong and best left to the programmer to specifically handle.  In your case, since there's a map, seems like you really want something to handle the relational mapping.  You shouldn't handle that in one DAO but write another DAO to take care of persisting it.

--Alex