Java APIs for Nashorn - Scripting in Java: Integrating with Groovy and JavaScript - page 315

The following snippet of code creates a Nashorn engine using a class filter, which is
an instance of the ClassFilter interface, to restrict the usage of any classes from the
com.jdojo package and its subpackages. Notice that the ClassFilter interface was
added in JDK8u40; it is not available in JDK8:

NashornScriptEngineFactory factory = new NashornScriptEngineFactory();
ScriptEngine engine = factory.getScriptEngine(clsName -> clsName.
startsWith("com.jdojo"));

ClassFilter is a functional interface. Its method is passed the fully qualified name
of the Java class that the Nashorn script is trying to use. If the method returns true , the
class can be used in the script; otherwise, the class cannot be used in the script.

■ If you do not want any Java classes to be exposed in scripts, you can use clsName
-> false as the lambda expression for the ClassFilter . Using a Java class in the script
that is restricted by the ClassFilter throws a java.lang.ClassNotFound exception.

Tip

The following is a list of the overloaded versions of the getScriptEngine() method
of the NashornScriptEngineFactory class:
•

ScriptEngine getScriptEngine()

•

ScriptEngine getScriptEngine(String... args)

•

ScriptEngine getScriptEngine(ClassFilter classFilter)

•

ScriptEngine getScriptEngine(ClassLoader appLoader)

•

ScriptEngine getScriptEngine(String[] args, ClassLoader
appLoader)

•

ScriptEngine getScriptEngine(String[] args, ClassLoader
appLoader, ClassFilter classFilter)

Sharing the Engine Globals
By default, the Nashorn engine maintains the global objects per script context. In this
discussion, the term “globals” means the global variables and declarations stored in the
global scope of the Nashorn script, which you refer to by this in the top-level scripts.
Do not mix up the global scope bindings in the script context with the globals in the
script. The script globals are searched first when you reference any variables or create
variables in your script. If you reference a variable in a script that is not found in the script
globals, the engine will search for it in the global scope bindings of the script context. For
example, the script objects Object , Math , String , and so on are part of the script globals.
Consider the program and its output in Listing 12-1.