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From Helios Alonso <halo...@atg.com.uy>
Subject Re: Dynamic Expressions for Struts-EL and JSTL
Date Thu, 02 Sep 2004 14:48:14 GMT
if you have a property in any bean you can write this:

myBean.theProperty

or

myBean['theProperty']

(I didn't use it but reading a tutorial it was a big surprise for me).

So, you could change this:

>String expr = "formBean." +
>((app.LayoutObject)pageContext.getAttribute("layoutObject")).getProperty();

to this:

formBean[pageContext.layoutObject.property]

(If I understood you have a layoutObject with a property saying which 
property read from formBean).

At 08:37 02/09/2004 -0500, you wrote:

>Hello,
>
>I'm using the Struts-EL and JSTL custom tag implementations in my Web app.
>
>I want to use the c:out tag to output dynamic data.  The tricky part is I
>want to dynamically build the EL expression at runtime by building up a
>String that should be evaluated.  I don't want to output the String, I want
>the String to be evaluated by the expression engine and then that written
>out.  An example follows below.
>
>
>
><%
>//Assume that after this line runs, expr has a value of
>formBean.property.value
>//This is the expression I want evaluated
>String expr = "formBean." +
>((app.LayoutObject)pageContext.getAttribute("layoutObject")).getProperty();
>
>pageContext.setAttribute("expr", expr);
>%>
>
><c:out value="Expression Value is: ${expr}" />
>
>
>
>The c:out tag above renders the text Expression Value is:
>formBean.property.value  .
>
>This isn't what I want -- I want it to evaluate the formBean.property.value
>down to an expression, and then spit out the value of that expression
>(basically, formBean.getProperty().getValue() ).
>
>Interestingly, if I "hard code" the expression, it works:
>
><c:out value="${formBean.property.value}"/>
>
>The only problem is I need to dynamically change this expression at runtime.
>
>Can this be done?  If so, how?  I'm hoping so otherwise I'll have a mountain
>of new code to write.  Also, is there a more elegant way to do what I show
>in the example above, like using tags instead of scriptlets?  I don't care
>if I use Struts-EL tags, JSTL tags, or both.
>
>Thank you very much!!
>
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