I was on the train this morning (usual inspiration zone-out) and got to
thinking about how in various work / business layer i access things like
DSN details or Hard-Drive locations (ie storage of xml dumps etc).
It occured to me, that maybe an object called PersistStorageBean (or maybe
even PersistBean) could be an object setup specifically for this.
The overall concept came about when I noticed that in some Models when
folk(s) use a DAO, they simply feed in DSN information (whether its DSN or
DSN,DSN_Username,DSN_Password etc). Typically most applications would
utilise a database, but in some cases its acceptable to simply store
information inside XML packets on a hard-drive (ie WDDX aswell). This
could also be mixed, in that in one case it stores information inside a
database, while in other parts it may want to store information on a
hard-drive. That or it has the typical Multiple DB DAO setup, where users
could nominate either to use a SQL storage, XML Storage or <insert your db
here> storage.
Point is, the DAO concept needs to be the only one that knows what
questions to ask for storage (ie "whats my DSN? whats my DSN Username (if
shared hosting) -OR- Where do i store serialized beans? where do i store
references etc).
I figured this is where a PersistStorageBean object could play a role,
here is some example code.
<cfscript>
var oBlogEntryBean =
createObject("component","entryBean").init(argumentCollection=arguments);
var persistStorageMemento =
this.getSingleton("model.myApp.utility.persistStorageBean").getMemento();
instance.getDAOFactory(arguments.persistType).getEntryDAO().create(persistStorageMemento,oBlogEntryBean);
</cfscript>
Now, it could simply use a Memento or a DTO for the getting information in
and out, but the point is the code above (ie Manager) doesn't have any
condition logic inside it, so it doesn't really care how information is
stored away.
The getDAOFactory() determines what type of persist layer this app will
use (either by passing in an argument or reverting to a default). Based on
this information, the appropriate DAO is slotted into place, which inside
that object is where it specifically asks the above questions (ie "if i'm
a DB, whats my DSN details -OR- If i'm a File Storage Layer, where do i
put things")
What's folks thoughts on this approach? Is it pattern abuse or will i face
problems (other then using file hard-drive systems for applications vs
databases.. but lets just say its a basic blog and its suitable for now)
eg properties inside the PersistStorageBean:
- storageLocation (location on the servers hard-drive to store files into
via the DAO's)
- datasourceName (or dsn)
- datasourceUsername (or dsn_u)
- datasourcePassword(or dsn_p)
- IsSharedHosting (You could use this property inside your DAO objects to
determine whether you need to insert the username/password for queries..
sharedhosting yes, internal no etc)
- .....
and so on....
Scott Barnes
http://www.mossyblog.com
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