-------------- Original message ----------------------
From: "Jacob Mathew" <[EMAIL PROTECTED]>
> I'm looking for documentation on implementing functions that can be
> used in EL in jsf pages. Maybe I'm missing something, but the best
> info I can find is that the a FunctionMapper object is used to resolve
> functions that show up in EL. But how can I define my own
> FunctionMapper? how do I set it? Can the default FunctionMapper be
> configured through an config file? I can't seem to find any info on
> this. Any reference will be much appreciated.
>
Using the EL functions in JSP is simpler than trying to use them in late bound
EL in JSF. First you need to create a static function and then register it in
a TLD [3]. Next, add the namespace to the page [4].
For example:
<c:set value="${tfun:formatDate(tfun:currentDate(), 'MM/dd/yyyy')}"
Invoking custom functions using JSF EL is more difficult. You can create your
own function mapper [1] and then use the ELContextWrapper [2] to register the
function mapper [1].
Using it would look something like this:
FacesContext context = FacesContext.getCurrentInstance();
// load function mapper with static methods from the TagFunctions
Method[] functions = TagFunctions.class.getMethods();
FunctionMapperImpl fm = new FunctionMapperImpl();
for (int i = 0; i < functions.length; i++)
{
if (Modifier.isStatic(functions[i].getModifiers()) &&
!Modifier.isNative(functions[i].getModifiers()))
{
String name = functions[i].getName();
fm.mapFunction("tfun", name, functions[i]);
}
}
//create an el context that implements a custom FunctionMapper; JSF 1.2
//RI implements a no-op function mapper
ELContextWrapper elContext =
new ELContextWrapper(context.getELContext(), fm);
// grap a reference to the EL factory
ExpressionFactory ef = context.getApplication().getExpressionFactory();
//create a value expression using the custom EL context wrapper
ValueExpression vs =
ef.createValueExpression(elContext,
"#{tfun:formatDate(tfun:currentDate(), 'MM/dd/yyyy')}",
String.class);
// return the value of the custom method el
return (String) vs.getValue(elContext);
}
[1]
https://svn.apache.org/viewvc/shale/framework/trunk/shale-test/src/main/java/org/apache/shale/test/el/MockFunctionMapper.java?view=markup
[2]
https://svn.apache.org/viewvc/tomcat/jasper/tc6.0.x/src/share/org/apache/jasper/el/ELContextWrapper.java?view=markup
[3]
<function>
<description>
Returns a formated date using the specified pattern.
</description>
<name>formatDate</name>
<function-class>demo.tfun.TagFunctions</function-class>
<function-signature>java.lang.String formatDate(java.util.Date,
java.lang.String)</function-signature>
<example>
tfun:formatDate( date , "MM/dd/yyyy")
</example>
</function>
[4]
<%@ taglib uri="http://demo.tfun"; prefix="tfun"%>
> -Jacob
