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Web Component Certification (OCEJWCD)

EL .(dot) operator

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posted 18 years ago

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If you check the HFSJ errata list on http://www.oreilly.com/catalog/headservletsjsp/errata/headservletsjsp.confirmed it says Question 17 Option C is invalid and should not be checked
....But I don't think that is correct....It is actually checked in the book though....
In fact, I did check it myself by tryin' it out on the system....If you use any of the 2 operators viz. . or [] and if you're tryin' to access a bean property which doesn't exist, then a runtime exception is thrown

[Note - We're talkin' about the condition when the bean exists(as an attribute in some scope) but the property does not...if the bean is non-existent as well, then you won't get an exception]

I would appreciate some help in this regard
[ November 28, 2006: Message edited by: Sayak Banerjee ]

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Marc Peabody

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posted 18 years ago

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It's been a while since I've run into this in the real world, but I'm pretty sure the EL simply doesn't print anything.

If you are getting a RuntimeException, it's probably from something else.

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Sayak Banerjee

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posted 18 years ago

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Thanks for your reply Mark...But here's a small piece of jsp code...You can try executing this jsp file to confirm what I mean....I've left annotations at the bottom of the page....Thanks in advance again

<html>
<body>

<jsp:useBean id="bean" class="java.lang.Object" scope="request" />

${bean.class}
${bean.lass}

</body>
</html>

class Object has a method getClass() ....${bean.class} works fine
class Object doesn't have a method getLass()....Therefore ${bean.lass} produces a Runtime Exception....You can try the two EL statements seperately to confirm the cause of the Exception
[ November 28, 2006: Message edited by: Sayak Banerjee ]

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Sreeraj G Harilal

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posted 18 years ago

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There is no need for a getter method to access class's instance object/variable for EL. But atleast you have to declare an instance variable or object of type that you want.

getter and setter is compulsory for <jsp:getProperty and <jsp:setProperty.Right?

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Marc Peabody

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posted 18 years ago

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My interpretation of "non-existant" was that the property is null, which won't print anything.

I tried your example and got an ELException, which is NOT a RuntimeException in Java EE 1.4 by the way - though it will be a RuntimeException in Java EE 5.

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Sayak Banerjee

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posted 18 years ago

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Ah...I see the point...Yup...Its an ELException indeed..not a RuntimeException....thanks for the clarification Marc

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