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Posted to dev@felix.apache.org by "Clement Escoffier (JIRA)" <ji...@apache.org> on 2009/05/01 09:13:30 UTC

[jira] Commented: (FELIX-1114) callback after configuration change needed

    [ https://issues.apache.org/jira/browse/FELIX-1114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12704909#action_12704909 ] 

Clement Escoffier commented on FELIX-1114:
------------------------------------------

Hi, 

There is not such method right now. But for the time being you can inject your properties inside a Dictionary or a Map. The setter method of this property will be called when a reconfiguration occurs. 
However this solution does not work with the configuration admin as config admin's configuration does not support map/dictionary properties.

I agree that such kind of method can be useful. But a couple of questions need to be answered before:

1) What kind of argument do you need in the updated method ? It will makes sense to push all the properties like:
@Updated
public void updatedConfiguration(Dictionary properties)
{
  // put changed configuration in use
}

2) Should this method be called at each configuration and reconfiguration (so, both at the beginning and at each reconfiguration) ? 


IMHO, such method must not create a POJO object if none exist, so it means that the method will be called after every configuration/reconfiguration only if a pojo object exist or wait for an object creation (and then be called ).

Clement


> callback after configuration change needed
> ------------------------------------------
>
>                 Key: FELIX-1114
>                 URL: https://issues.apache.org/jira/browse/FELIX-1114
>             Project: Felix
>          Issue Type: Improvement
>          Components: iPOJO
>    Affects Versions: iPOJO-1.2.0
>            Reporter: Ron Koerner
>
> It often occurs that a configuration/property change requires some work to be done. If only a single property is affected method injection can be used.
> If multiple properties are changed and these changes are kind of an atomic transaction, there is no (sensible) way to tell the service to use the new values.
> Imagine a service listening on a port and writing the output to a file. The service has the two string properties "port" and "file". When the service is validated, it opens a listening port and a writable file according to the properties. Now imagine it is either dangerous to have a port input written to the wrong file or opening ports and files is very costly or there is already an object doing the work for us but it needs to be constructed with port number and filename and cannot be changed at runtime. Therefore we cannot use method injection like
> @Property(name="port")
> public void setPort(String port)
> {
>    incomingSocket.close();
>    incomingSocket=new IncomingSocket(port);
> }
> because that is costly and leaves the possibility to have things written to the wrong file.
> Therefore something like
> @Updated
> public void updatedConfiguration()
> {
>   // put changed configuration in use
> }
> is needed. The method annotated with @Updated (or specified in XML) is to called after all the configuration changes are done.
> Right now, the only way is to stop and start the service since only one ManagedService per PID is recognized by ConfigurationAdmin.

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