You should realize that the LHS ("when") and RHS ("then") are different and use different syntaxes.
The RHS is essentially java... you can't use ":" and "from".

Also.. "Event(..) from .." is a pattern - a filter that tries to match existing objects asserted in the WM.
What you need there is to create a new Event.. just do it the way you would in Java.

You will have to learn to read error messages, too.
What the error is trying to say, is that it interpreted the Event( .. ) statement as a method call,
which is of course undefined.

On 03/10/2014 08:19 PM, Sandhya Sree wrote:
i tried this :

rule "new file"
when
    FileData($old : fileOld, $new : fileNew, fileOld != fileNew)
    $newFile : String( this not memberOf $old ) from $new
then   
    
event : Event("file added", filename, new Date()) from $plus
    Event.listOfEvents.add(event);
    event.display(); 
end


this gives the following error:
The method Event(String, File, Date) is undefined for the type Rule_new_file_0c90fff8d9b74b439ab79971b13b75ac
 Syntax error on token "from", ; expected
 $plus cannot be resolved to a type
 Syntax error on token ".", ; expected
 listOfEvents cannot be resolved


On Tue, Mar 11, 2014 at 12:09 AM, Davide Sottara <dsotty@gmail.com> wrote:
"from" will iterate for you, exactly like "accumulate" counted the events.
If you need more details, please consult the documentation



On 03/10/2014 07:29 PM, Sandhya Sree wrote:
The problem here is even if multiple files are added, there is only one event object created. i want to have like say if 3 new files are added, 3 event objects must be created, and all three event objects must be added to List<Event> listOfEvents. 


Thanks.


On Mon, Mar 10, 2014 at 11:48 PM, Davide Sottara <dsotty@gmail.com> wrote:
The "accumulates" should not be in the "then" part of a rule (see my previous email).
That rule gave you two lists, in the variables $plus and $mins, that you can use in the consequence.

If you need to process each file separately, you may want to do something like this:

rule "new file"
when
    FileData($old : fileOld, $new : fileNew, fileOld != fileNew)
    $newFile : String( this not memberOf $old ) from $new
then  
   // create new event for a new file : new Event(...)
   // add to list : Event.listOfEvents.add(...)
end

You'll need another rule for the files that have been removed.

Notice that your Event class has no way to distinguish "added" from "removed" files, you may want to
add a boolean or something there.
Best
Davide


On 03/10/2014 07:04 PM, 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.

i also have another class called Event which is as follows:
public class Event {
public static String name;
private  File source;
private  Date timeStamp;
        public  static  List<Event> listOfEvents = new ArrayList<Event>();
 
public Event(String name, File source, Date timeStamp) {
this.name = name;
this.source = source;
this.timeStamp = timeStamp;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public File getSource() {
return source;
}
public void setSource(File source) {
this.source = source;
}
public Date getTimeStamp() {
return timeStamp;
}
public void setTimeStamp(Date timeStamp) {
this.timeStamp = timeStamp;
}

now i have to compare these two lists(fileOld and fileNew) in a rule file and if they are not equal i have to create an event object for every file added and deleted and put it in the List<Event> listOfEvents.

here is my rule file:

rrule "files are equal"
    when 
         FileData( fileOld == fileNew)
    then
       System.out.println("files are equal");
    end


rule "files not equal"
when
    FileData($old : fileOld, $new : fileNew, fileOld != fileNew)
    
then
   accumulate( $s : String( this not memberOf $old ) from $new, $plus : collectList( $s ) ) 
   accumulate( $t : String( this not memberOf $new ) from $old, $mins : collectList( $t ) ) 
   System.out.println("files added:" + $plus ); 
   System.out.println( "files deleted:" + $mins );
end



how can i loop through each of the file added or deleted and create an Event Class object for every file added and deleted  and finally add all the created objects to List<Event> listOfEvents..


Thanks.


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