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From "Kwok, Grace" <grace.k...@msci.com>
Subject [jexl] setFunctions and JexlContext
Date Wed, 01 Feb 2012 01:19:36 GMT
Hi,
Could someone explain to me what this mean in actual code?
setFunctions
If the entry value is a class that has one contructor taking a JexlContext as argument, an
instance of the namespace will be created at evaluation time. It might be a good idea to derive
a JexlContext to carry the information used by the namespace to avoid variable space pollution
and strongly type the constructor with this specialized JexlContext.

http://commons.apache.org/jexl/apidocs/index.html

I would like my function to be able to access one of the variable set in the JexlContext.
It sound like I should do something like this.

Public class FunctionClass

{
                Public FunctionClass(JexlContext jexlContext)
                {....}

                Public doSomethingWithVariableA()
                {...}
}

JexlContext jc = new MapContext();
Map<String, Object> funcs = new HashMap<String, Object>();
funcs.put(null, new FunctionClass(jc));
CustomJexlEngine jexl = new JexlEngine();
jexl.setFunctions(funcs);
Jc.put("a", "myPreciousValue");
Expression e11 = jexl.createExpression("doSomethingWithVariableA()");
Object result1 = e11.evaluate(jc);

Then my methods in FunctionClass can access the jexlContext and access variable "a".  However,
I don't understand the paragraph about "avoiding variable space pollution".


Thanks, Grace




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