> Hi, I'm relatively new to both Java and Drools. I'm trying to figure out how
> to use maps in Drools. I've looked at the thread
>
http://www.mail-archive.com/rules-users@lists.jboss.org/msg09802.html
>
>>From what I've read generally it seems best to insert objects directly
> rather than use nested accessors. So I've been experimenting with trying to
> insert a map and then checking stuff in it.
>
> I set up a simple test map of String to Integer, with just "a" as key and 1
> as value, and "b" with 2.
> Map<String, Integer> map = new HashMap<String, Integer>();
> map.put("a", 1);
> map.put("b", 2);
> String a = "a";
>
> I then inserted the map and also inserted the String a of value "a".
>
> Here's the test rule, with various things I tried commented out:
>
> rule "testing maps"
> dialect "mvel"
> when
> $str: String()
> // $m: Map( this[$str] == 1 ) # error
> // $m: Map( this.$str == 1 ) # error
> // $m: Map( this["$str"] == 1 ) # compiles but rule won't fire
> $m: Map( this["a"] == 1 ) # this works however!
> then
> System.out.println($m[$str]); #also works with String and Map objects & no
> conditions
> end
>
> It obviously doesn't like it when I try to use the String object as the key
> for the map. But it works when I use a String literal as the key. What am I
> doing wrong?
>
> Does anyone have any suggestions please, or shall I give up and either use
> eval as mentioned in
>
http://www.mail-archive.com/rules-users@lists.jboss.org/msg09716.html or use
> the map as a field of another object which I insert instead of the map (in
> fact that was my original plan!)?