Passing Parameters to Scripts - Scripting in Java: Integrating with Groovy and JavaScript - page 28

At this point, you can visualize the state of the ScriptContext instance as shown in
Figure 3-1 .
Figure 3-1. A pictorial view of an instance of the SimpleScriptContext class
You can perform several operations on a ScriptContext . You can set a different
value for an already stored key using the setAttribute(String name, Object value,
int scope) method. You can remove a key-value pair using the removeAttribute(String
name, int scope) method for a specified key and a scope. You can get the value of a key
in the specified scope using the getAttribute(String name , int scope) method.
The most interesting thing that you can do with a ScriptContext is to retrieve a
key value without specifying its scope using its getAttribute(String name) method. A
ScriptContext searches for the key in the engine scope Bindings first. If it is not found in
the engine scope, the Bindings in the global scope is searched. If the key is found in these
scopes, the corresponding value from the scope, in which it is found first, is returned. If
neither scope contains the key, null is returned.
In your example, you have stored the key named year in the engine scope as well as
in the global scope. The following snippet of code returns 1969 for the key year from the
engine scope as the engine scope is searched first. The return type of the getAttribute()
method is Object .
// Get the value of the key year without specifying the scope.
// It returns 1969 from the Bindings in the engine scope.
int yearValue = (Integer)ctx.getAttribute("year");
You have stored the key named name only in the global scope. If you attempt to
retrieve its value, the engine scope is searched first, which does not return a match.
Subsequently, the global scope is searched and the value "Boni" is returned, as shown:
// Get the value of the key named name without specifying the scope.
// It returns "Boni" from the Bindings in the global scope.
String nameValue = (String)ctx.getAttribute("name");