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Synchronous HD Items and Values [message #1631599]

Mon, 23 February 2015 17:01

Eclipse User

Hello,
I have a scenario where we need to get the hd item tags and values synchronously rather using the listeners?

1. Are listeners the "only" way to get the data? If not, can you please provide the class or a sample that can be achieved synchronously. Any already existing tests would be grateful.

2. I am following your HMI HD Client and trying to see if you already have something like this.

Thanks for the great project!!!

krishna

Re: Synchronous HD Items and Values [message #1632867 is a reply to message #1631599]

Tue, 24 February 2015 09:32

Eclipse User

Hi,

yes, right now listeners are the only way for Java. There still is the HTTP interface which is synchronous.

However it is pretty easy to make an asynchronous call synchronous by just waiting for the listener to notify the state change to complete.

Jens

Re: Synchronous HD Items and Values [message #1633230 is a reply to message #1632867]

Tue, 24 February 2015 14:05

Eclipse User

Thanks Jen for the prompt reply - will try that!!!

Krishna

Re: Synchronous HD Items and Values [message #1633249 is a reply to message #1633230]

Tue, 24 February 2015 14:22

Eclipse User

Jen,
I see that the query has an update state notification, is there a similiar one for item retreival. I would like to know when am done retreiving the items/tags. I am looking at ListItemListener and only see ListChanged?

Appreciate it,

Krishna

Re: Synchronous HD Items and Values [message #1634597 is a reply to message #1633249]

Wed, 25 February 2015 05:52

Eclipse User

Hi,

you mean for DA items?

Jens

On 02/24/2015 08:22 PM, Krishna KK wrote:
> Jen,
> I see that the query has an update state notification, is there a
> similiar one for item retreival. I would like to know when am done
> retreiving the items/tags. I am looking at ListItemListener and only see
> ListChanged?
>
> Appreciate it,
>
> Krishna

Re: Synchronous HD Items and Values [message #1635040 is a reply to message #1634597]

Wed, 25 February 2015 10:39

Eclipse User

Jen,
Sorry, I meant HD items. Here is the code that am referring to:

import org.eclipse.scada.hd.ItemListListener;
import org.eclipse.scada.hd.client.Connection;
import org.eclipse.scada.hd.data.HistoricalItemInformation;

public class ItemListObserver implements ItemListListener
{

private final Map<String, HistoricalItemInformation> items = new HashMap<String, HistoricalItemInformation> ();

public ItemListObserver ( final Connection connection)
{
synchronized ( this )
{
connection.addListListener ( this );
}
}

@Override
public void listChanged ( final Set<HistoricalItemInformation> addedOrModified, final Set<String> removed, final boolean full )
{
handleUpdate ( addedOrModified, removed, full );
}

Is there a way for me to find if the retrieval is complete in the ItemListListener or should I be using a different approach?

Appreciate your help,

Regards,
Krishna

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