Passing Parameters to Scripts - Scripting in Java: Integrating with Groovy and JavaScript - page 38

■ By default, all scriptengines that a ScriptEngineManager creates share its
Bindings as their global scope Bindings . if you use the setBindings() method of a
ScriptEngine to set its global scope Bindings or if you use the setBindings() method of
a ScriptEngineManager to set its Bindings , you break the “globalness” chain as discussed
in this section. to keep the “globalness” chain intact, you should always use the put()
method of the ScriptEngineManager to add key-value pairs to its Bindings . to remove a
key-value pair from the global scope of all scriptengines created by a ScriptEngineManager ,
you need to get the reference of the Bindings using the getBindings() method of the
ScriptEngineManager and use the remove() method on the Bindings .

Tip

Using a Custom ScriptContext
In the previous section, you saw that each ScriptEngine has a default script context. The
get() , put() , getBindings() , and setBindings() methods of the ScriptEngine operate
on its default ScriptContext . When no ScriptContext is specified to the eval() method
of the ScriptEngine , the default context of the engine is used. The following two versions
of the eval() method of the ScriptEngine use its default context to execute the script:
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Object eval(String script)

Object eval(Reader reader)
You can pass a Bindings to the following two versions of the eval() method:
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Object eval(String script, Bindings bindings)

Object eval(Reader reader, Bindings bindings)
These versions of the eval() method do not use the default context of the
ScriptEngine . They use a new ScriptContext whose engine scope Bindings is the one
passed to these methods and the global scope Bindings is the same as for the default
context of the engine. Note that these two versions of the eval() method keep the default
context of the ScriptEngine untouched.
You can pass a ScriptContext to the following two versions of the eval() method:
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Object eval(String script, ScriptContext context)

Object eval(Reader reader, ScriptContext context)
These versions of the eval() method use the specified context to execute the script.
They keep the default context of the ScriptEngine untouched.

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