[Catalyst] Dispatching with Chained vs HTTP method

Adam Clarke adam.clarke at strategicdata.com.au
Wed May 7 06:30:12 BST 2008

On 07/05/2008, at 11:05 AM, Toby Corkindale wrote:

> Ah, I was thinking of transactions vs a REST API, eg:
>    PUT /user/1234/account_balance?subtract=1
>    POST /user/4567/account_balance?add=1
> Since those are two separate HTTP requests, and REST specifically  
> states you
> cannot maintain state on the server, how would you perform those two
> operations inside a transaction?
> (My "solution" is to implement it in one request, like:
>    PUT /user/1234/money_transfer?user=4567;amount=1
> However that is not CRUD-like, nor a direct mapping of DBIC  
> functionality to

The solution suggested in "Restful Web Services" is to POST to a  
"factory" resource which creates you with a transaction resource. e.g.  
"POST /transactions/account-transfer" returns "Location:  / 
transactions/account-transfer/11a5", where the 11a5 is a unique  
transaction identifier.

Then "PUT /transactions/account-transfer/11a5/accounts/checking/11",  
where 11 is the account identifier. The body carries the transaction  
details, in the example the balances are adjusted absolutely, i.e.  
"balance=150". A similar PUT is sent for the other account.

Once the required components of the transaction have been PUT it is  
possible to rollback by DELETEing the transaction resource or commit  
it by putting "committed=true" to the resource.

While seeming a bit fiddly, it does keep the state on the client and  
allows the client to make (at least some of) the commit / rollback  
decision rather than (only) the server.


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