Wednesday, December 16, 2009

Thing you should know about jsp:useBean Tag

* When you are using a class in the use bean tag and the class was not found in the given scope say "request", then use:bean tag will NOT throw any exceptions. Insted it will create the class and access the value in it.

* When you want to set a property to a bean, only if the bean is empty. Then your set:property tag shoud be inside the use:bean body tag as below.
So name property will be set only if the men object was not found the page scope, else the setProperty will not be executed.

* You cannot use any abstact Class as your class attribute in your use:bean tag.And the class should follow the Bean Law ;)

* When you want use Reference type to a object in a use:bean Tag, type attribute saves you.below is the example.

Person class which we declared in type attribute can be abstact and should follow the inhertance relasionship with the class attribute. Else thing will blow up ;)
* You can use only type attribute in use:bean without your class attribute ,ONLY IF a object is already avaiable in the scope with the given use:bean id.
if their no attributes aviable in the page scope with the vaue "testvariable", then thing will blow up ;)

* You can easy map the HTML form elements value, to the jsp:setProperty tag by specifying the param attribute. And you can start forgetting request.getParamenter() here after.
* You can easy set all the form HTML tag values to your bean class easly by setting param="*", it will set all the form HTML elemnts values to your bean property.
But with one CONDITION, your name in the HTML form element and the property name in the bean should match.
 * useBean tag, is used mostly to print a string value or to print the primitive types. When you want to access (or play) with a Object inside the bean. Then you need help from EL expression guy.

* We will discuss more about EL Tags in upcoming post ;). Thats it for now ...

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