Re: how to dynamically evaluate expression in java code running inside groovy

[Ravi]

Thanks for your explanation Jason. This helped me understand the core 
issue and I can easily find many workarounds.

Another followup question. Is it possible to execute the code within 
context? I found this article, tried to replicate in java but it 
wouldn't work. Is it possible to do something like this in Java?

http://www.sdidit.nl/2012/12/groovy-dsl-executing-scripts-within.html




On 7/8/2015 12:24 PM, Winnebeck, Jason wrote:
When you run a GroovyShell execute it is like you are creating a class
with that code in it. The “printme” variable is a local variable to the
method, so it cannot be seen outside of that method. Using Groovy
doesn’t allow you do violate the scope of Java – a class can’t know the
local variables of the method that created/called it.

You have to do what you say, that is put into the shell’s binding all of
the variables that you might possibly use, which is the common strategy
for this problem. A class to hold all of the data can be used if you
want to limit the number of bindings (i.e. some kind of state class).
The closest that you can get to what you are doing is to transform all
of the local variables you want to access into instance fields and then
set “this” into the binding.

Jason

*From:*Ravi Kapoor [mailto:ravikapoor...@gmail.com]
*Sent:* Wednesday, July 08, 2015 3:11 PM
*To:* users@groovy.incubator.apache.org
*Subject:* how to dynamically evaluate expression in java code running
inside groovy

I am trying to run my whole java project in Groovy.

I have run into an issue i.e. anytime I want to do anything dynamically,
I have to bind all possible things that may exist inside the expression.

This is very inefficient.

Instead I want to be able to pass my existing context to groovy shell.
How do I do this?

I am attaching a sample program highlighting the issue. This seems such
an easy and obvious feature, but I am so stuck here. Thanks for helping.

Ravi

--------------------------------------------------------------------------------

package com.test;

import java.util.HashMap;

import java.util.Map;

import groovy.lang.*;

public class Test {

             public static void main(String[] args) {

                         GroovyClassLoader classLoader = new
GroovyClassLoader();

             Binding binding = new Binding();

             Map<Object, Object> attributes = new HashMap<Object, Object>();

             GroovyShell shell = new GroovyShell(classLoader, binding);

             binding.setVariable("shell", shell);

                         shell.evaluate("new
com.test.Test().runInsideGroovy(shell)");

             }

             public void runInsideGroovy(GroovyShell shell) {

                         System.out.println("inside groovy");

                         String printme = "secret";

                         shell.evaluate("System.err.println(printme)");

             }

}

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