Passing Parameters to Scripts - Scripting in Java: Integrating with Groovy and JavaScript - page 47

Summary
You can pass parameters to the script using the ScriptContext . An instance of the
Bindings interface serves as the parameter holder. The Bindings interface inherits from
the Map interface imposing a restriction that its keys must be nonempty, non-null String s.
The SimpleBinding class is an implementation of the Bindings interface. It is preferred
to use the createBindings() method of ScriptEngine to get an instance of the Bindings
interface giving ScriptEngine a chance to returned a specialized implementation of the
Bindings interface. A Bindings is associated with a scope that can be an engine scope
or a global scope. Parameters passed in the engine scope takes precedence over the
parameters passed in the global scope. Parameters passed can be local to a script engine,
local to a script execution, or global to all script engines created by a ScriptManager .
A script engine executes a script in a context that consists of four components: a set
of Bindings , where each Bindings is associated with a different scope, a Reader that is
used by the script engine to read inputs, a Writer that is used by the script engine to write
outputs, and an error Writer that is used by the script engine to write error outputs. An
instance of the ScriptContext interface represents a context for the script execution. The
SimpleScriptContext class is an implementation of the ScriptContext interface.
The set of Bindings in a context is used to pass parameters to the script. A reader
and writers in a context control input source and output destinations of the script,
respectively. For example, by setting a file writer as a writer, you can send all outputs from
a script to a file. Every ScriptEngine has a default ScriptContext that is used to execute
scripts when no ScriptContext is passed to the eval() method. The getContext()
method of ScriptEngine returns the default context of the engine. You can also pass a
separate ScriptContext with the eval() method that will be used to execute your script,
leaving the default ScriptContext of the engine untouched.