[rules-users] problem with drools

[Sandhya Sree]

thanks Davide. that was really helping.
i get the output displayed twice.
what can i do about it.


On Fri, Feb 28, 2014 at 8:50 PM, Davide Sottara <dsotty at gmail.com> wrote:

>  There are a few errors in the rules
>
> 1)
> not FileData( fileOld == fileNew )
> will fire either 1) when there is a FileData with different lists OR 2)
> when there is no FileData at all in the workingMemory
>
> 2)
> the rule should not compile, unless fileOld and fileNew are STATIC fields
> of the class FileData. Is this the case? If so, why?
> The problem is that the rule will fire also when there is no FileData in
> the WM, so calling the function there is pointless
>
> Your rule should be rewritten as : (notice that the != operator is
> overloaded, so it correctly computes "not equals")
>
> FileData( fileOld != fileNew )
>
> 3) To do what you want, you don't even need the function - if you prefer
> to use functions and code, consider dropping Drools.
> A possible rule-based approach to your problem is this:
>
> rule "Deltas"
> when
>     FileData( $old : fileOld, $new : fileNew, fileOld != fileNew )
>     accumulate( $s : String( this not memberOf $old ) from $new, $plus :
> collectList( $s ) )
>     accumulate( $t : String( this not memberOf $new ) from $old, $mins :
> collectList( $t ) )
> then
>     System.out.println( $plus );
>     System.out.println( $mins );
> end
>
> The other rule is fine.
>
> Best
> Davide
>
>
>
> On 02/28/2014 09:54 AM, Sandhya Sree wrote:
>
> hi,
> im new to drools..im trying to create a project as follows. i have a class
> called Monitor  which monitors a folder and creates two lists called
> fileOld( which is the list of filenames in that folder at time t1)  and
> fileNew(which is the list of filenames in that folder at time t2). i have
> another class called FileData which contains two members fileOld and
> fileNew (list of strings) with getters,setters and constructor. fileOld and
> fileNew from Monitor Class are passed to FileData class.
>
>  now i have to compare these two lists in a rule file and if they are not
> equal i have to print the lists of files added/ deleted. how to do this in
> drools.
>
>  here is my rule file:
>
>  rule "files are equal"
>
>     when
>         FileData(fileOld == fileNew)
>
>     then
>        System.out.println("files are equal");
>
>
>  end
>
>  rule "files not equal"
>
>    when
>         not FileData(fileOld == fileNew)
>     then
>        System.out.println("files are not equal");
>        difference(FileData.getFileOld(),FileData.getFileNew());
>
>  end
>
>
>  function void difference(List fileOld, List fileNew)
> {
>
>
>     ArrayList<String> add = new ArrayList<String>(fileNew);
>    add.removeAll(fileOld);
>    System.out.println("files Added: " + add);
>
>     ArrayList<String> remove = new ArrayList<String>(fileOld);
>    remove.removeAll(fileNew);
>    System.out.println("files Removed: " + remove);
> }
>
>
>  but this displays the following error...
>
>  Rule Compilation error : [Rule name='files not equal']
> Cannot make a static reference to the non-static method getFileOld() from
> the type FileData
> Cannot make a static reference to the non-static method getFileNew() from
> the type FileData
>
>
>
>  what can be done??
>
>
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