Scoping in embedded groovy scripts - scripting

Question

In my app, I use Groovy as a scripting language. To make things easier for my customers, I have a global scope where I define helper classes and constants.
Currently, I need to run the script (which builds the global scope) every time a user script is executed:
context = setupGroovy();
runScript( context, "global.groovy" ); // Can I avoid doing this step every time?
runScript( context, "user.groovy" );
Is there a way to setup this global scope once and just tell the embedded script interpreter: "Look here if you can't find a variable"? That way, I could run the global script once.
Note: Security is not an issue here but if you know a way to make sure the user can't modify the global scope, that's an additional plus.

Answer 1

Shamelessly stolen from groovy.codehaus :
The most complete solution for people
who want to embed groovy scripts into
their servers and have them reloaded
on modification is the
GroovyScriptEngine. You initialize the
GroovyScriptEngine with a set of
CLASSPATH like roots that can be URLs
or directory names. You can then
execute any Groovy script within those
roots. The GSE will also track
dependencies between scripts so that
if any dependent script is modified
the whole tree will be recompiled and
reloaded.
Additionally, each time you run a
script you can pass in a Binding that
contains properties that the script
can access. Any properties set in the
script will also be available in that
binding after the script has run. Here
is a simple example:
/my/groovy/script/path/hello.groovy:
output = "Hello, ${input}!"
import groovy.lang.Binding;
import groovy.util.GroovyScriptEngine;
String[] roots = new String[] { "/my/groovy/script/path" };
GroovyScriptEngine gse = new GroovyScriptEngine(roots);
Binding binding = new Binding();
binding.setVariable("input", "world");
gse.run("hello.groovy", binding);
System.out.println(binding.getVariable("output"));
This will print "Hello, world!".
Found: here
Would something like that work for you?

Answer 2

A simple solution is to use the code from groovy.lang.GroovyShell: You can precompile the script like so:
GroovyCodeSource gcs = AccessController.doPrivileged( new PrivilegedAction<GroovyCodeSource>() {
public GroovyCodeSource run() {
return new GroovyCodeSource( scriptCode, fileName, GroovyShell.DEFAULT_CODE_BASE );
}
} );
GroovyClassLoader loader = AccessController.doPrivileged( new PrivilegedAction<GroovyClassLoader>() {
public GroovyClassLoader run() {
return new GroovyClassLoader( parentLoader, CompilerConfiguration.DEFAULT );
}
} );
Class<?> scriptClass = loader.parseClass( gcs, false );
That's was the expensive part. Now use InvokeHelper to bind the compiled code to a context (with global variables) and run it:
Binding context = new javax.script.Binding();
Script script = InvokerHelper.createScript(scriptClass, context);
script.run();