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  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
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  25 
  26 /**
  27 Provides the implementation of Nashorn script engine and 
  28 the runtime environment for programs written in ECMAScript 5.1.
  29 <p>
  30 Nashorn is a runtime environment for programs written in ECMAScript 5.1.
  31 </p>
  32 <h1>Usage</h1>
  33 The recommended way to use Nashorn is through the <a href="http://jcp.org/en/jsr/detail?id=223" target="_top">JSR-223
  34 "Scripting for the Java Platform"</a> APIs found in the {@link javax.script} package. Usually, you'll obtain a
  35 {@link javax.script.ScriptEngine} instance for Nashorn using:
  36 <pre>
  37 import javax.script.*;
  38 ...
  39 ScriptEngine nashornEngine = new ScriptEngineManager().getEngineByName("nashorn");
  40 </pre>
  41 and then use it just as you would any other JSR-223 script engine. See
  42 <a href="jdk/nashorn/api/scripting/package-summary.html">{@code jdk.nashorn.api.scripting}</a> package
  43 for details.
  44 <h1>Compatibility</h1>
  45 Nashorn is 100% compliant with the <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm"
  46 target="_top">ECMA-262 Standard, Edition 5.1</a>. It requires a Java Virtual Machine that implements the
  47 <a href="http://jcp.org/en/jsr/detail?id=292" target="_top">JSR-292 "Supporting Dynamically Typed Languages on the Java
  48 Platform"</a> specification (often referred to as "invokedynamic"), as well as the already mentioned JSR-223.
  49 <h1>Interoperability with the Java platform</h1>
  50 In addition to being a 100% ECMAScript 5.1 runtime, Nashorn provides features for interoperability of the ECMAScript
  51 programs with the Java platform. In general, any Java object put into the script engine's context will be visible from
  52 the script. In terms of the standard, such Java objects are not considered "native objects", but rather "host objects",
  53 as defined in section 4.3.8. This distinction allows certain semantical differences in handling them compared to native
  54 objects. For most purposes, Java objects behave just as native objects do: you can invoke their methods, get and set
  55 their properties. In most cases, though, you can't add arbitrary properties to them, nor can you remove existing
  56 properties.
  57 <h2>Java collection handling</h2>
  58 Native Java arrays and {@link java.util.List}s support indexed access to their elements through the property accessors,
  59 and {@link java.util.Map}s support both property and element access through both dot and square-bracket property
  60 accessors, with the difference being that dot operator gives precedence to object properties (its fields and properties
  61 defined as {@code getXxx} and {@code setXxx} methods) while the square bracket operator gives precedence to map
  62 elements. Native Java arrays expose the {@code length} property.
  63 <h2>ECMAScript primitive types</h2>
  64 ECMAScript primitive types for number, string, and boolean are represented with {@link java.lang.Number},
  65 {@link java.lang.CharSequence}, and {@link java.lang.Boolean} objects. While the most often used number type is
  66 {@link java.lang.Double} and the most often used string type is {@link java.lang.String}, don't rely on it as various
  67 internal optimizations cause other subclasses of {@code Number} and internal implementations of {@code CharSequence} to
  68 be used.
  69 <h2>Type conversions</h2>
  70 When a method on a Java object is invoked, the arguments are converted to the formal parameter types of the Java method
  71 using all allowed ECMAScript conversions. This can be surprising, as in general, conversions from string to number will
  72 succeed according to Standard's section 9.3 "ToNumber" and so on; string to boolean, number to boolean, Object to
  73 number, Object to string all work. Note that if the Java method's declared parameter type is {@code java.lang.Object},
  74 Nashorn objects are passed without any conversion whatsoever; specifically if the JavaScript value being passed is of
  75 primitive string type, you can only rely on it being a {@code java.lang.CharSequence}, and if the value is a number, you
  76 can only rely on it being a {@code java.lang.Number}. If the Java method declared parameter type is more specific (e.g.
  77 {@code java.lang.String} or {@code java.lang.Double}), then Nashorn will of course ensure the required type is passed.
  78 <h2>SAM types</h2>
  79 As a special extension when invoking Java methods, ECMAScript function objects can be passed in place of an argument
  80 whose Java type is so-called "single abstract method" or "SAM" type. While this name usually covers single-method
  81 interfaces, Nashorn is a bit more versatile, and it recognizes a type as a SAM type if all its abstract methods are
  82 overloads of the same name, and it is either an interface, or it is an abstract class with
  83 a no-arg constructor. The type itself must be public, while the constructor and the methods can be either public or
  84 protected. If there are multiple abstract overloads of the same name, the single function will serve as the shared
  85 implementation for all of them, <em>and additionally it will also override any non-abstract methods of the same name</em>.
  86 This is done to be consistent with the fact that ECMAScript does not have the concept of overloaded methods.
  87 <h2>The {@code Java} object</h2>
  88 Nashorn exposes a non-standard global object named {@code Java} that is the primary API entry point into Java
  89 platform-specific functionality. You can use it to create instances of Java classes, convert from Java arrays to native
  90 arrays and back, and so on.
  91 <h2>Other non-standard built-in objects</h2>
  92 In addition to {@code Java}, Nashorn also exposes some other non-standard built-in objects:
  93 {@code JSAdapter}, {@code JavaImporter}, {@code Packages}
  94 
  95 @provides javax.script.ScriptEngineFactory
  96 @moduleGraph
  97 @since 9
  98  */
  99 module jdk.scripting.nashorn {
 100     requires java.logging;
 101     requires transitive java.scripting;
 102     requires jdk.dynalink;
 103 
 104     exports jdk.nashorn.api.scripting;
 105     exports jdk.nashorn.api.tree;
 106 
 107     exports jdk.nashorn.internal.runtime to
 108         jdk.scripting.nashorn.shell;
 109     exports jdk.nashorn.internal.objects to
 110         jdk.scripting.nashorn.shell;
 111     exports jdk.nashorn.tools to
 112         jdk.scripting.nashorn.shell;
 113 
 114     provides javax.script.ScriptEngineFactory
 115         with jdk.nashorn.api.scripting.NashornScriptEngineFactory;
 116 
 117     provides jdk.dynalink.linker.GuardingDynamicLinkerExporter
 118         with jdk.nashorn.api.linker.NashornLinkerExporter;
 119 }