jdk/src/share/classes/javax/script/package.html

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<p>The scripting API consists of interfaces and classes that define
Java <font size=1><sup>TM</sup></font> Scripting Engines and provides
a framework for their use in Java applications. This API is intended
for use by application programmers who wish to execute programs
written in scripting languages in their Java applications. The
scripting language programs are usually provided by the end-users of
the applications. 
</p>
<p>The main areas of functionality of <code>javax.script</code>
package include 
</p>
<ol>
	<li><p><b>Script execution</b>: Scripts
	are streams of characters used as sources for  programs executed by
	script engines. Script execution uses 
        {@link javax.script.ScriptEngine#eval eval} methods of
	{@link javax.script.ScriptEngine ScriptEngine} and methods of the 
        {@link javax.script.Invocable Invocable} interface. 
	</p>
	<li><p><b>Binding</b>: This facility
	allows Java objects to be exposed to script programs as named
	variables. {@link javax.script.Bindings Bindings} and 
        {@link javax.script.ScriptContext ScriptContext}
	classes are used for this purpose. 
	</p>
	<li><p><b>Compilation</b>: This
	functionality allows the intermediate code generated by the
	front-end of a script engine to be stored and executed repeatedly.
	This benefits applications that execute the same script multiple
	times. These applications can gain efficiency since the engines'
	front-ends only need to execute once per script rather than once per
	script execution. Note that this functionality is optional and
	script engines may choose not to implement it. Callers need to check
	for availability of the {@link javax.script.Compilable Compilable}
        interface using an <I>instanceof</I> check. 
	</p>
	<li><p><b>Invocation</b>: This
	functionality allows the reuse of intermediate code generated by a
	script engine's front-end. Whereas Compilation allows entire scripts
	represented by intermediate code to be re-executed, Invocation
	functionality allows individual procedures/methods in the scripts to
	be re-executed. As in the case with compilation, not all script
	engines are required to provide this facility. Caller has to check
	for {@link javax.script.Invocable Invocable} availability. 
	</p>
	<li><p><b>Script engine discovery and Metadata</b>: Applications
	written to the Scripting API might have specific requirements on
	script engines. Some may require a specific scripting language
	and/or version while others may require a specific implementation
	engine and/or version. Script engines are packaged in a specified
	way so that engines can be discovered at runtime and queried for
	attributes. The Engine discovery mechanism is based on the Service
	discovery mechanism described in the <b>Jar File Specification</b>.
	Script engine implementing classes are packaged in jar files that
	include a  text resource named
	<b>META-INF/services/javax.script.ScriptEngineFactory</b>. This
	resource must include a line for each 
        {@link javax.script.ScriptEngineFactory ScriptEngineFactory}
	that is packaged in the jar file. 
        {@link javax.script.ScriptEngineManager ScriptEngineManager}
	includes 
        {@link javax.script.ScriptEngineManager#getEngineFactories getEngineFactories} method to get all
	{@link javax.script.ScriptEngineFactory ScriptEngineFactory} instances 
        discovered using this mechanism. <code>ScriptEngineFactory</code> has 
        methods to query attributes about script engine.
	</p>
</ol>

@since 1.6

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