Java's Getters And Setters are evil, JavaFX Script's not always

The reaction for the posts Getters and setters: an antipattern. JavaBeans and OO and Summary: Public getters and setters should be considered as an antipattern caused some interesting discussions and comments. There was one common sense: exposing private attributes over getters and setters is neither objectoriented, nor domain driven style. An interesting solution for this problem offers JavaFX script, sample:


A class customer with 2 members and one update method:


import java.lang.System;

class Customer{

private attribute firstName: String?;

private attribute lastName: String?;

operation update(newFirstName:String,newLastName:String);

}

 

operation Customer.update(newFirstName:String,newLastName:String){

firstName = newFirstName;

lastName = newLastName;

}


The interesting part of the source code are "Replace Trigger" which can be associated with attributes: 


trigger on Customer.firstName[oldValue] = newValue{

System.out.println("Old value was: {oldValue}, the new value is: {newValue}");

}

 

trigger on Customer.lastName[oldValue] = newValue{

System.out.println("Old value was: {oldValue}, the new value is: {newValue}");

}

 

The construction of an FX object:

 

var dukeCustomer = Customer{

firstName: "duke"

lastName: "mighty"

};



Causes the following output:


Old value was: , the new value is: duke
Old value was: , the new value is: mighty


The call of the following update method: 


dukeCustomer.update('java','javafx');


writes the lines below:


Old value was: duke, the new value is: java
Old value was: mighty, the new value is: javafx



So JavaFX Script allows, only if neccessary, the definition of "interceptors" called triggers, which can be used for validation etc.

I like the idea, because most of the Java-Getters/Setters are empty. I'm curious, why these triggers aren't called "update aspects".

It would be much better for the marketing :-).

The method update isn't necessary, it is also allowed to access the attributes directly. It seem's like JavaFX now ignores the "private" keyword...


Hint: to see the system output from the JavaFXPad, you have to activate the "Java Console" in the JNLP settings (System Settings, Java under Windows).


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Comments:

The getters and setters debate has been raging for awhile now. Not sure where I stand but interesting twise with the JavaFX factor.

Posted by JavaDonkey on June 01, 2007 at 06:52 PM CEST #

Sort of unrelated but I'm also impressed by the integration of database concepts... It's clear the design team around F3/JavaFX (Christopher only?) are well-rounded, in-the-trenches type of people.

Posted by Ivan on June 01, 2007 at 07:12 PM CEST #

I just came here because I read your J1 presentation where you discuss binding JPA objects to UI using 295... I was very surprised to see something like that, have you tried this?
295 requires property change listeners in order to build proper two way binding, that doesn't seem like a good idea to add into a JPA object (PropertyChangeSupport objects). Yet I didn't see any mention of that in the presentation.

Anyway, regarding getters and setters have you seen my bean properties project?

It pretty much addresses most of the issues and I think solves them more elegantly than F3 (arguably the syntax could be improved).

Posted by Shai Almog on June 03, 2007 at 12:21 AM CEST #

Hi Shai,

the problem with J1-presentation is the 1 hour limit :-). I used Eclipse's Beans Binding, my own jakarta commons beanutils based solution and I'm also experimenting with Beans Binding. PropertyChangeSupport stuff is not perfect, but can be easily generated (see Netbeans 6 -> Java Desktop Application). A two-way binding is only needed in case there are more than one view interested in one domain projects. The JavaFX solution surprised me - it is interesting.
I'm already curious about your solution!

thank you for your comment,

adam

Posted by Adam Bien on June 03, 2007 at 11:50 AM CEST #

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