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Message from discussion Scala and databases
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Konstantinos Kougios  
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 More options Nov 2 2012, 5:59 pm
From: Konstantinos Kougios <kostas.koug...@googlemail.com>
Date: Fri, 02 Nov 2012 21:58:48 +0000
Local: Fri, Nov 2 2012 5:58 pm
Subject: Re: [scala-user] Re: Scala and databases
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Thanks for the example Flavio, ok I see. Why the emphasis on
transactional memory and efficient memory usage? What apps are you
targeting?  Also what's your naming conventions for mapping to the tables?

mapperdao uses a different approach and your example would look like

class Stock(val code:String,val categories:Set[Category]) // or
List[Category] etc
class Category(val name:String,val stocks:Set[Stock])

You can too use an intermediate StockCategory entity if you prefer.

MapperDao gives direct control on persistence and transactions to client
code, i.e.

val tx = Transaction.get(txManager, Propagation.Nested,
Isolation.ReadCommited, -1)
// will insert category and insert/update related Stock in 1 transaction
val inserted = tx { () =>
     mapperDao.insert(CategoryEntity, category)

}

MapperDao supports nested transactions too along with updates/deletes.
All web frameworks are supported as mapperdao only needs a DataSource to
work. A major feature of mapperdao is support for immutable classes,
something that i.e. hibernate doesn't support, along with a typesafe DSL
for querying.

On 02/11/12 20:06, Flávio W. Brasil wrote:

> Hello.

> Activate is designed to be simple. OO is straightforward to map data
> and relations. Instead of trying to create a magical relational
> many-to-many concept, you do as should do in OO: create a relation entity.

> class Stock(var code: String) extends Entity {
> def categories = select[StockCategory].where(_.stock :==
> this).map(_.category)
> }
> class Category(var name: String) extends Entity {
> def stocks = select[StockCategory].where(_.category :== this).map(_.stock)
> }
> case class StockCategory(stock: Stock, category: Category) extends Entity

> To map the same domain using separate entity declaration and
> "implicit" many-to-many relation you have to produce much more code.
> Activate 1.1 version (to be released this month) has support for Lists
> too:

> class Person(var name: String, var contacts: List[Contact]) extends Entity

> There are characteristics that makes Activate different from Slick,
> Mapperdao, Squeryl, Hibernate, etc.
> For example: transparent persistence, optimistic locking with read and
> write validation, nested transactions, efficient memory usage, design
> by contract, migrations dsl,  relational and non relational database
> support, mass update/delete, play framework support.
> It's a new way to do persistence: simple, highly scalable and consistent.

> --
> Flávio W. Brasil
> http://activate-framework.org
> {persistence as it should be}

> On Thursday, 1 de November de 2012 at 19:43, Konstantinos Kougios wrote:

>> I had a look at activate, I couldn't find a complete example with say
>> a many-to-many relationship between 2 entities. From the table DDL to
>> mappings (if any) and some queries. Do you have a link?

>> On 01/11/12 12:52, Rafał Krzewski wrote:
>>> W dniu czwartek, 1 listopada 2012 11:50:07 UTC+1 użytkownik
>>> Konstantinos Kougios napisał:
>>>> There doesn't seem to be other ORM tools for Scala.

>>> Well, there is at least one other:
>>> https://github.com/fwbrasil/activate :)

>>> Cheers,
>>> Rafał


 
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