List the current {@code Configuration} objects which match the filter.
Only {@code Configuration} objects with non- {@code null} properties areconsidered current. That is, {@code Configuration.getProperties()} isguaranteed not to return {@code null} for each of the returned{@code Configuration} objects.
When there is no security on then all configurations can be returned. If security is on, the caller must have ConfigurationPermission[location,CONFIGURE].
The syntax of the filter string is as defined in the {@link Filter}class. The filter can test any configuration properties including the following:
- {@code service.pid} - the persistent identity
- {@code service.factoryPid} - the factory PID, if applicable
- {@code service.bundleLocation} - the bundle location
The filter can also be {@code null}, meaning that all {@code Configuration} objects should be returned.
@param filter A filter string, or {@code null} to retrieve all{@code Configuration} objects.
@return All matching {@code Configuration} objects, or {@code null} ifthere aren't any.
@throws IOException if access to persistent storage fails
@throws InvalidSyntaxException if the filter string is invalid
@security ConfigurationPermission[c.location,CONFIGURE] Onlyconfigurations {@code c} are returned for which the caller hasthis permission