[rules-users] Possible to use functions in DRL when dialect is mvel?

[Stephen Masters]

Okay Wolfgang ... you asked for it. Here's a version which takes it pretty much to the minimum.

The error I see is "Unable to resolve method using strict-mode: mypackage.CloneMessage.cloneMessage(mypackage.Message)"

However, the error is only seen when I use mvel dialect. The working Java dialect rule is also included below.

Note that when I re-wrote the example function to take a common type such as String as argument, then the mvel version worked. It's when the argument is a declared type that it fails.

Thanks for taking a look,

Steve



file - MessageFact.drl

    package mypackage

    declare Message
        Text: String
    end



file - CloneMessage.drl

    package mypackage

    function Message cloneMessage(Message originalMessage) {

        Message newMessage = new Message();
        newMessage.setText(originalMessage.getText());
        return newMessage;

    }



file - SayHelloRuleJava.drl

    package mypackage

    rule "Say hello"
        dialect "java"
        lock-on-active true
        when
            # Always
        then
            Message originalMessage = new Message();
            originalMessage.setText("Hello, World!");

            Message clonedMessage = cloneMessage(originalMessage);

            insert(clonedMessage);
    end



file - SayHelloRuleMvel.drl

    package mypackage

    rule "Say hello"
        dialect "mvel"
        lock-on-active true
        when
            # Always
        then
            Message originalMessage = new Message();
            originalMessage.Text = "Hello, World!";

            Message clonedMessage = cloneMessage(originalMessage);

            insert(clonedMessage);
    end



On Jun 19, 2012, at 12:27 PM, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:

Can you please provide an example where and how you import and use a
DRL function so that it works/doesn't work with MVEL/Java?

-W


On 19/06/2012, Stephen Masters <stephen.masters at me.com> wrote:
> Hi folks,
>
> Is it possible to refer to DRL functions from a DRL when the dialect is
> mvel?
>
> I have been working on unit tests for a rule that were consistently failing
> due to not being able to find the function that should be imported. Having
> tried various formats (the documentation is rather unhelpful here) for the
> import, I thought I'd see what happened if I just switched to the Java
> dialect. Suddenly it worked without even needing an import statement.
>
> Unfortunately, this forces me to switch from the neat ...
> newFact.Property = otherFact.Property
> ... to the rather ugly Java-style
> newFact.setProperty(otherFact.getProperty())
>
> So I would quite like to know if there is an undocumented (or
> well-hidden-documented) mechanism for using functions when in mvel dialect.
> Or am I stuck with switching to Java?
>
> Thanks in advance for any pointers anybody can provide,
>
> Steve
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