[jboss-dev-forums] [JBoss OSGi Development] - Re: Use Drools for the Bundle Resolver

[tirelli]

If you want to check that there is no other WireCandidate besides the one matched, you could use "not":


  | rule "Use WireCandidate"
  | when
  |     $import : ImportPackage( exporter == null )
  |     $wc : WireCandidate( importPackage == $import )
  |     not( WireCandidate( this != $wc, importPackage == $import ) )
  | then
  |     System.out.println("Use WireCandidate " + $wc.getImportPackage() + " --> " + $wc.getExportPackage());
  |     modify ( $wc.getImportPackage() ) { setExporter( $wc.getExportPackage() ) };
  |     retract ( $wc );
  | end
  | 

Now, if you want a more general way of counting instances, use the count() function on accumulate:


  | rule "Use WireCandidate"
  | when
  |     $import : ImportPackage( exporter == null )
  |     $wc : WireCandidate( importPackage == $import )
  |     // checks if the is exactly 1 instance
  |     Number( intValue == 1 ) from accumulate( 
  |                 $c : WireCandidate( importPackage == $import ),
  |                 count($c) )
  | then
  |     System.out.println("Use WireCandidate " + $wc.getImportPackage() + " --> " + $wc.getExportPackage());
  |     modify ( $wc.getImportPackage() ) { setExporter( $wc.getExportPackage() ) };
  |     retract ( $wc );
  | end
  | 

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