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+ − 1 <!--
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+ − 2 Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
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+ − 3 DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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+ − 5 This code is free software; you can redistribute it and/or modify it
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+ − 24 -->
+ − 25 <body>
+ − 26 <p>
+ − 27 Nashorn is a runtime environment for programs written in ECMAScript 5.1.
+ − 28 </p>
+ − 29 <h1>Usage</h1>
+ − 30 <p>
+ − 31 The recommended way to use Nashorn is through the <a href="http://jcp.org/en/jsr/detail?id=223" target="_top">JSR-223
+ − 32 "Scripting for the Java Platform"</a> APIs found in the {@link javax.script} package. Usually, you'll obtain a
+ − 33 {@link javax.script.ScriptEngine} instance for Nashorn using:
+ − 34 <pre>
+ − 35 import javax.script.*;
+ − 36 ...
+ − 37 ScriptEngine nashornEngine = new ScriptEngineManager().getEngineByName("nashorn");
+ − 38 </pre>
+ − 39 and then use it just as you would any other JSR-223 script engine. See
+ − 40 <a href="jdk/nashorn/api/scripting/package-summary.html">{@code jdk.nashorn.api.scripting}</a> package
+ − 41 for details.
+ − 42 <p>
+ − 43 <h1>Compatibility</h1>
+ − 44 Nashorn is 100% compliant with the <a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm"
+ − 45 target="_top">ECMA-262 Standard, Edition 5.1</a>. It requires a Java Virtual Machine that implements the
+ − 46 <a href="http://jcp.org/en/jsr/detail?id=292" target="_top">JSR-292 "Supporting Dynamically Typed Languages on the Java
+ − 47 Platform"</a> specification (often referred to as "invokedynamic"), as well as the already mentioned JSR-223.
+ − 48 <h1>Interoperability with the Java platform</h1>
+ − 49 <p>
+ − 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 <p>
+ − 58 <h2>Java collection handling</h2>
+ − 59 <p>
+ − 60 Native Java arrays and {@link java.util.List}s support indexed access to their elements through the property accessors,
+ − 61 and {@link java.util.Map}s support both property and element access through both dot and square-bracket property
+ − 62 accessors, with the difference being that dot operator gives precedence to object properties (its fields and properties
+ − 63 defined as {@code getXxx} and {@code setXxx} methods) while the square bracket operator gives precedence to map
+ − 64 elements. Native Java arrays expose the {@code length} property.
+ − 65 <p>
+ − 66 <h2>ECMAScript primitive types</h2>
+ − 67 <p>
+ − 68 ECMAScript primitive types for number, string, and boolean are represented with {@link java.lang.Number},
+ − 69 {@link java.lang.CharSequence}, and {@link java.lang.Boolean} objects. While the most often used number type is
+ − 70 {@link java.lang.Double} and the most often used string type is {@link java.lang.String}, don't rely on it as various
+ − 71 internal optimizations cause other subclasses of {@code Number} and internal implementations of {@code CharSequence} to
+ − 72 be used.
+ − 73 <p>
+ − 74 <h2>Type conversions</h2>
+ − 75 <p>
+ − 76 When a method on a Java object is invoked, the arguments are converted to the formal parameter types of the Java method
+ − 77 using all allowed ECMAScript conversions. This can be surprising, as in general, conversions from string to number will
+ − 78 succeed according to Standard's section 9.3 "ToNumber" and so on; string to boolean, number to boolean, Object to
+ − 79 number, Object to string all work. Note that if the Java method's declared parameter type is {@code java.lang.Object},
+ − 80 Nashorn objects are passed without any conversion whatsoever; specifically if the JavaScript value being passed is of
+ − 81 primitive string type, you can only rely on it being a {@code java.lang.CharSequence}, and if the value is a number, you
+ − 82 can only rely on it being a {@code java.lang.Number}. If the Java method declared parameter type is more specific (e.g.
+ − 83 {@code java.lang.String} or {@code java.lang.Double}), then Nashorn will of course ensure the required type is passed.
+ − 84 <p>
+ − 85 <h2>SAM types</h2>
+ − 86 <p>
+ − 87 As a special extension when invoking Java methods, ECMAScript function objects can be passed in place of an argument
+ − 88 whose Java type is so-called "single abstract method" or "SAM" type. While this name usually covers single-method
+ − 89 interfaces, Nashorn is a bit more versatile, and it recognizes a type as a SAM type if all its abstract methods are
+ − 90 overloads of the same name, and it is either an interface, or it is an abstract class with
+ − 91 a no-arg constructor. The type itself must be public, while the constructor and the methods can be either public or
+ − 92 protected. If there are multiple abstract overloads of the same name, the single function will serve as the shared
+ − 93 implementation for all of them, <em>and additionally it will also override any non-abstract methods of the same name</em>.
+ − 94 This is done to be consistent with the fact that ECMAScript does not have the concept of overloaded methods.
+ − 95 <p>
+ − 96 <h2>The {@code Java} object</h2>
+ − 97 Nashorn exposes a non-standard global object named {@code Java} that is the primary API entry point into Java
+ − 98 platform-specific functionality. You can use it to create instances of Java classes, convert from Java arrays to native
+ − 99 arrays and back, and so on. The methods on the objects are directly implemented by public static methods on the class
+ − 100 <a href="jdk/nashorn/internal/objects/NativeJava.html">{@code NativeJava}</a>, see that class for details on what
+ − 101 functionality is available.
+ − 102 <h2>Representations of Java types</h2>
+ − 103 The method <a href="jdk/nashorn/internal/objects/NativeJava.html#type(java.lang.Object,%20java.lang.Object)">
+ − 104 {@code Java.type(typeName)}</a> takes a name of a type, and returns an object representing a Java type. You can
+ − 105 use that object to both create new instances of Java classes, as well as to access static fields and methods on them.
+ − 106 The type object is distinct from the {@code java.lang.Class} object, which represents the reflective run-time type
+ − 107 identity and doesn't carry i.e. static members. Again, see the link for {@code NativeJava} above for details.
+ − 108 <h2>Other non-standard built-in objects</h2>
+ − 109 In addition to {@code Java}, Nashorn also exposes some other non-standard built-in objects:
+ − 110 <a href="jdk/nashorn/internal/objects/NativeJSAdapter.html">{@code JSAdapter}</a>,
+ − 111 <a href="jdk/nashorn/internal/objects/NativeJavaImporter.html">{@code JavaImporter},
+ − 112 <a href="jdk/nashorn/internal/runtime/NativeJavaPackage.html">{@code Packages}.</a>
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+ − 113 </body>