Here's a start, please anyone correct me if I've made any mistakes...
public class ListLDM extends LoadableDetachableModel<List> {
private String id;
public ListLDM(List l, String id) {
//constructor with primed model
super(l);
this.id = id;
}
public ListLDM(String id) {
//constructor with empty model
this.id = id;
}
@Override
protected List load() {
return service.getList(id);
}
}
From: John Owen <[email protected]>
To: "[email protected]" <[email protected]>
Date: 02/28/2011 05:35 PM
Subject: RE: Perfomance of IDataProvider
An example with a list would be quite useful.
Regards
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Monday, February 28, 2011 3:10 PM
To: [email protected]
Subject: Re: Perfomance of IDataProvider
If I understand where you are going I completely agree the example is a
little misleading. Some ways to think about it differently...
"id" is synonymous with "a small sub-set of the entire result-set which
can be used to rehydrate the detached model"
The model is the data you want to provide to a repeater for instance, so
this can be a single Contact model (one query for each row) or a
ContactList (one query per page with pagination). Retrieving a list
instead of each contact individually would be more efficient.
If you need an example let me know...
From: Juansoft <[email protected]>
To: [email protected]
Date: 02/28/2011 03:53 PM
Subject: Re: Perfomance of IDataProvider
First render thanks for your replies.
@vov: If i use this:
public IModel<Entity> model(Entity entity)
{
return new Model<Entity>(entity);
}
In this case the memory footprint of the session grows because you return
Model object that is not a transient object(or this is what I've read in
wicket documentation...!!) . ¿This means that if you dataview have 100
rows
you have 100 Model<Entity> stored in your session?
¿To avoid this do not exist LoadableDetachableModel what is detached after
page rendering?
@James Carman:
This is the aspect of the most LoadableDetachableModel used in DataView
examples. Specifically in wicket official examples. For each row in
DataView
this create new DetachableContactModel , store his ID. After in method
populateItem of Dataview, getModelObject() call result in direct call to
DetachableContactModel.load() that again return object to a database.
Using hibernate this object is cached (or so I have understood), but if
use
hand made DAO (like me) that simply query and return a POJO populated this
result in more database conections and querys! Am I right?
public class DetachableContactModel extends LoadableDetachableModel
{
private long id;
protected ContactsDatabase getContactsDB()
{
return DatabaseLocator.getDatabase();
}
/**
* @param c
*/
public DetachableContactModel(Contact c)
{
this(c.getid())
}
/**
* @param id
*/
public DetachableContactModel(long id)
{
if (id == 0)
{
throw new IllegalArgumentException();
}
this.id = id;
}
/**
* @see java.lang.Object#hashCode()
*/
public int hashCode()
{
return Long.valueOf(id).hashCode();
}
/**
* used for dataview with ReuseIfModelsEqualStrategy item reuse
strategy
*
* @see org.apache.wicket.markup.repeater.ReuseIfModelsEqualStrategy
* @see java.lang.Object#equals(java.lang.Object)
*/
public boolean equals(final Object obj)
{
if (obj == this)
{
return true;
}
else if (obj == null)
{
return false;
}
else if (obj instanceof DetachableContactModel)
{
DetachableContactModel other = (DetachableContactModel)obj;
return other.id == this.id;
}
return false;
}
/**
* @see org.apache.wicket.model.LoadableDetachableModel#load()
*/
@Override
protected Object load()
{
// loads contact from the database
return getContactsDB().get(id);
}
}
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