[rules-dev] Fine Grained Property Change Listeners (Slot Specific)

[Geoffrey De Smet]

Hi Mario,

Here are a few suggestions

1) Fail fast in this case:
> this annotation has no effect if the corresponding pattern's type 
> hasn't been annotated with @PropSpecific
Fail Fast with an exception like this:
   throw new IllegalStateException("The factClass (" + factClass + ") 
has a property (" + property + ") that has a @Modifies annotation, but 
the class isn't annotated with @PropSpecific.");
If for a later version, we receive user input that there is actually a 
good case where @Modifies exists without @PropSpecific, we can always 
allow it (vica versa is not possible).

2) @Modifies( "firstName, lastName" ) should not put the comma (,) 
inside the quotes. Go for:
   @Modifies( "firstName", "lastName" )
   or @ModifiesCombination( @Modifies("firstName"), @Modifies("lastName") )
The last way might look a bit strange, but it's a common practice, for 
example in JPA-hibernate:
   
http://docs.jboss.org/hibernate/core/4.0/javadocs/org/hibernate/annotations/ColumnTransformers.html
   
http://docs.jboss.org/hibernate/core/4.0/javadocs/org/hibernate/annotations/ColumnTransformer.html
That last way won't break when there are additional properties on the 
@Modifies annotations (while the other approaches will):
    @ModifiesCombination( @Modifies("firstName", whenImplementsInterface 
= FirstNameable.class), @Modifies("lastName", whenImplementsInterface = 
LastNameable.class) )

3) What's the point of doing a @PropSpecific on a field instead of a class?
> declare Person
>     @propSpecific
>     firstName : String

4) I also believe we should stick to Java naming conventions [1] as 
close as possible because the main target audience to start using our 
drools jars is the java programmers audience.
The stranger our stuff looks to them, the more likely they 'll try to 
write "a simple solution" themselves instead of using our "complex" 
framework.
4a) Like Edson says: start with a capital like all other annotations.
> * I think we should keep the property names consistent between the 
> java and the declare element, so I suggest you use uppercase for both 
> (@PropSpecific).
4b) The naming conventions also state not to abbreviate to fast, so I 'd 
prefer @PropertySpecific over @PropSpecific


[1] Oracle's Java coding conventions, which are the base for JBoss's 
coding conventions:
http://www.oracle.com/technetwork/java/codeconv-138413.html

Op 17-01-12 20:20, Mario Fusco schreef:
> Hi all,
>
> just a quick recap of what I did until now to check if we are all on 
> the same page and also agree with the naming convention I used.
>
> The property specific feature is off by default in order to make the 
> behavior of the rule engine backward compatible with the former 
> releases. If you want to activate it on a specific bean you have to 
> annotate it with @propSpecific. This annotation works both on drl type 
> declarations:
>
> declare Person
>     @propSpecific
>     firstName : String
>     lastName : String
> end
>
> and on Java classes:
>
> @PropSpecific
> public static class Person {
>     private String firstName;
>     private String lastName;
> }
>
> Moreover on Java classes you can also annotate any method to say that 
> its invocation actually modifies other properties. For instance in the 
> former Person class you could have a method like:
>
> @Modifies( "firstName, lastName" )
> public void setName(String name) {
>     String[] names = name.split("\\s");
>     this.firstName = names[0];
>     this.lastName = names[1];
> }
>
> That means that if a rule has a RHS like the following:
>
> modify($person) { setName("Mario Fusco") }
>
> it will correctly recognize that both the firstName and lastName have 
> been modified and act accordingly. Of course the @Modifies annotation 
> on a method has no effect if the declaring class isn't  annotated with 
> @PropSpecific.
>
> The third annotation I have introduced is on patterns and allows you 
> to modify the inferred set of properties "listened" by it. So, for 
> example, you can annotate a pattern in the LHS of a rule like:
>
> Person( firstName == $expectedFirstName ) @watch( lastName ) // --> 
> listens for changes on both firstName (inferred) and lastName
> Person( firstName == $expectedFirstName ) @watch( * ) // --> listens 
> for all the properties of the Person bean
> Person( firstName == $expectedFirstName ) @watch( lastName, !firstName 
> ) // --> listens for changes on lastName and explicitly exclude firstName
> Person( firstName == $expectedFirstName ) @watch( *, !age ) // --> 
> listens for changes on all the properties except the age one
>
> Once again this annotation has no effect if the corresponding 
> pattern's type hasn't been annotated with @PropSpecific.
>
> I've almost finished with the development of this feature (at the 
> moment I am missing the compile-time check of the properties named in 
> the @watch annotation together with some more exhaustive tests), so if 
> you think that I misunderstood something or there is room for any 
> improvement (or you just don't like the annotation's names I chose) 
> please let me know as soon as possible.
>
> Mario
>
>
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-- 
With kind regards,
Geoffrey De Smet

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