Mercurial > hg > openjdk > jigsaw > nashorn
view src/jdk/nashorn/internal/objects/NativeJava.java @ 174:5eb1427b6a6d
8011544: Allow subclassing Java classes from script without creating instances
Reviewed-by: jlaskey, sundar
author | attila |
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date | Thu, 04 Apr 2013 15:53:26 +0200 |
parents | c54e218333be |
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/* * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package jdk.nashorn.internal.objects; import static jdk.nashorn.internal.runtime.ECMAErrors.typeError; import static jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED; import java.lang.reflect.Array; import java.util.Collection; import jdk.internal.dynalink.beans.StaticClass; import jdk.internal.dynalink.support.TypeUtilities; import jdk.nashorn.internal.objects.annotations.Attribute; import jdk.nashorn.internal.objects.annotations.Function; import jdk.nashorn.internal.objects.annotations.ScriptClass; import jdk.nashorn.internal.objects.annotations.Where; import jdk.nashorn.internal.runtime.JSType; import jdk.nashorn.internal.runtime.ScriptObject; import jdk.nashorn.internal.runtime.linker.JavaAdapterFactory; /** * This class is the implementation for the {@code Java} global object exposed to programs running under Nashorn. This * object acts as the API entry point to Java platform specific functionality, dealing with creating new instances of * Java classes, subclassing Java classes, implementing Java interfaces, converting between Java arrays and ECMAScript * arrays, and so forth. */ @ScriptClass("Java") public final class NativeJava { private NativeJava() { } /** * Returns true if the specified object is a Java type object, that is an instance of {@link StaticClass}. * @param self not used * @param type the object that is checked if it is a type object or not * @return tells whether given object is a Java type object or not. * @see #type(Object, Object) */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object isType(final Object self, final Object type) { return type instanceof StaticClass; } /** * <p> * Given a name of a Java type, returns an object representing that type in Nashorn. The Java class of the objects * used to represent Java types in Nashorn is not {@link java.lang.Class} but rather {@link StaticClass}. They are * the objects that you can use with the {@code new} operator to create new instances of the class as well as to * access static members of the class. In Nashorn, {@code Class} objects are just regular Java objects that aren't * treated specially. Instead of them, {@link StaticClass} instances - which we sometimes refer to as "Java type * objects" are used as constructors with the {@code new} operator, and they expose static fields, properties, and * methods. While this might seem confusing at first, it actually closely matches the Java language: you use a * different expression (e.g. {@code java.io.File}) as an argument in "new" and to address statics, and it is * distinct from the {@code Class} object (e.g. {@code java.io.File.class}). Below we cover in details the * properties of the type objects. * </p> * <p><b>Constructing Java objects</b></p> * Examples: * <pre> * var arrayListType = Java.type("java.util.ArrayList") * var intType = Java.type("int") * var stringArrayType = Java.type("java.lang.String[]") * var int2DArrayType = Java.type("int[][]") * </pre> * Note that the name of the type is always a string for a fully qualified name. You can use any of these types to * create new instances, e.g.: * <pre> * var anArrayList = new Java.type("java.util.ArrayList") * </pre> * or * <pre> * var ArrayList = Java.type("java.util.ArrayList") * var anArrayList = new ArrayList * var anArrayListWithSize = new ArrayList(16) * </pre> * In the special case of inner classes, you need to use the JVM fully qualified name, meaning using {@code $} sign * in the class name: * <pre> * var ftype = Java.type("java.awt.geom.Arc2D$Float") * </pre> * However, once you retrieved the outer class, you can access the inner class as a property on it: * <pre> * var arctype = Java.type("java.awt.geom.Arc2D") * var ftype = arctype.Float * </pre> * <p> * You can access both static and non-static inner classes. If you want to create an instance of a non-static * inner class, remember to pass an instance of its outer class as the first argument to the constructor. * </p> * <p> * If the type is abstract, you can instantiate an anonymous subclass of it using an argument list that is * applicable to any of its public or protected constructors, but inserting a JavaScript object with functions * properties that provide JavaScript implementations of the abstract methods. If method names are overloaded, the * JavaScript function will provide implementation for all overloads. E.g.: * </p> * <pre> * var TimerTask = Java.type("java.util.TimerTask") * var task = new TimerTask({ run: function() { print("Hello World!") } }) * </pre> * <p> * Nashorn supports a syntactic extension where a "new" expression followed by an argument is identical to * invoking the constructor and passing the argument to it, so you can write the above example also as: * </p> * <pre> * var task = new TimerTask { * run: function() { * print("Hello World!") * } * } * </pre> * <p> * which is very similar to Java anonymous inner class definition. On the other hand, if the type is an abstract * type with a single abstract method (commonly referred to as a "SAM type") or all abstract methods it has share * the same overloaded name), then instead of an object, you can just pass a function, so the above example can * become even more simplified to: * </p> * <pre> * var task = new TimerTask(function() { print("Hello World!") }) * </pre> * <p> * Note that in every one of these cases if you are trying to instantiate an abstract class that has constructors * that take some arguments, you can invoke those simply by specifying the arguments after the initial * implementation object or function. * </p> * <p>The use of functions can be taken even further; if you are invoking a Java method that takes a SAM type, * you can just pass in a function object, and Nashorn will know what you meant: * </p> * <pre> * var timer = new Java.type("java.util.Timer") * timer.schedule(function() { print("Hello World!") }) * </pre> * <p> * Here, {@code Timer.schedule()} expects a {@code TimerTask} as its argument, so Nashorn creates an instance of a * {@code TimerTask} subclass and uses the passed function to implement its only abstract method, {@code run()}. In * this usage though, you can't use non-default constructors; the type must be either an interface, or must have a * protected or public no-arg constructor. * </p> * <p> * You can also subclass non-abstract classes; for that you will need to use the {@link #extend(Object, Object...)} * method. * </p> * <p><b>Accessing static members</b></p> * Examples: * <pre> * var File = Java.type("java.io.File") * var pathSep = File.pathSeparator * var tmpFile1 = File.createTempFile("abcdefg", ".tmp") * var tmpFile2 = File.createTempFile("abcdefg", ".tmp", new File("/tmp")) * </pre> * Actually, you can even assign static methods to variables, so the above example can be rewritten as: * <pre> * var File = Java.type("java.io.File") * var createTempFile = File.createTempFile * var tmpFile1 = createTempFile("abcdefg", ".tmp") * var tmpFile2 = createTempFile("abcdefg", ".tmp", new File("/tmp")) * </pre> * If you need to access the actual {@code java.lang.Class} object for the type, you can use the {@code class} * property on the object representing the type: * <pre> * var File = Java.type("java.io.File") * var someFile = new File("blah") * print(File.class === someFile.getClass()) // prints true * </pre> * Of course, you can also use the {@code getClass()} method or its equivalent {@code class} property on any * instance of the class. Other way round, you can use the synthetic {@code static} property on any * {@code java.lang.Class} object to retrieve its type-representing object: * <pre> * var File = Java.type("java.io.File") * print(File.class.static === File) // prints true * </pre> * <p><b>{@code instanceof} operator</b></p> * The standard ECMAScript {@code instanceof} operator is extended to recognize Java objects and their type objects: * <pre> * var File = Java.type("java.io.File") * var aFile = new File("foo") * print(aFile instanceof File) // prints true * print(aFile instanceof File.class) // prints false - Class objects aren't type objects. * </pre> * @param self not used * @param objTypeName the object whose JS string value represents the type name. You can use names of primitive Java * types to obtain representations of them, and you can use trailing square brackets to represent Java array types. * @return the object representing the named type * @throws ClassNotFoundException if the class is not found */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object type(final Object self, final Object objTypeName) throws ClassNotFoundException { return type(objTypeName); } private static StaticClass type(final Object objTypeName) throws ClassNotFoundException { return StaticClass.forClass(type(JSType.toString(objTypeName))); } private static Class<?> type(final String typeName) throws ClassNotFoundException { if (typeName.endsWith("[]")) { return arrayType(typeName); } return simpleType(typeName); } /** * Returns name of a java type {@link StaticClass}. * @param self not used * @param type the type whose name is returned * @return name of the given type */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object typeName(final Object self, final Object type) { if (type instanceof StaticClass) { return ((StaticClass)type).getRepresentedClass().getName(); } else if (type instanceof Class) { return ((Class<?>)type).getName(); } else { return UNDEFINED; } } /** * Given a JavaScript array and a Java type, returns a Java array with the same initial contents, and with the * specified component type. Example: * <pre> * var anArray = [1, "13", false] * var javaIntArray = Java.toJavaArray(anArray, "int") * print(javaIntArray[0]) // prints 1 * print(javaIntArray[1]) // prints 13, as string "13" was converted to number 13 as per ECMAScript ToNumber conversion * print(javaIntArray[2]) // prints 0, as boolean false was converted to number 0 as per ECMAScript ToNumber conversion * </pre> * @param self not used * @param objArray the JavaScript array. Can be null. * @param objType either a {@link #type(Object, Object) type object} or a String describing the component type of * the Java array to create. Can not be null. If undefined, Object is assumed (allowing the argument to be omitted). * @return a Java array with the copy of JavaScript array's contents, converted to the appropriate Java component * type. Returns null if objArray is null. * @throws ClassNotFoundException if the class described by objType is not found */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object toJavaArray(final Object self, final Object objArray, final Object objType) throws ClassNotFoundException { final StaticClass componentType = objType instanceof StaticClass ? (StaticClass)objType : objType == UNDEFINED ? StaticClass.forClass(Object.class) : type(objType); if (objArray == null) { return null; } Global.checkObject(objArray); return ((ScriptObject)objArray).getArray().asArrayOfType(componentType.getRepresentedClass()); } /** * Given a Java array or {@link Collection}, returns a JavaScript array with a shallow copy of its contents. Note * that in most cases, you can use Java arrays and lists natively in Nashorn; in cases where for some reason you * need to have an actual JavaScript native array (e.g. to work with the array comprehensions functions), you will * want to use this method. Example: * <pre> * var File = Java.type("java.io.File") * var listHomeDir = new File("~").listFiles() * var jsListHome = Java.toJavaScriptArray(listHomeDir) * var jpegModifiedDates = jsListHome * .filter(function(val) { return val.getName().endsWith(".jpg") }) * .map(function(val) { return val.lastModified() }) * </pre> * @param self not used * @param objArray the java array or collection. Can be null. * @return a JavaScript array with the copy of Java array's or collection's contents. Returns null if objArray is * null. */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object toJavaScriptArray(final Object self, final Object objArray) { if (objArray == null) { return null; } else if (objArray instanceof Collection) { return new NativeArray(((Collection<?>)objArray).toArray()); } else if (objArray instanceof Object[]) { return new NativeArray(((Object[])objArray).clone()); } else if (objArray instanceof int[]) { return new NativeArray(((int[])objArray).clone()); } else if (objArray instanceof double[]) { return new NativeArray(((double[])objArray).clone()); } else if (objArray instanceof long[]) { return new NativeArray(((long[])objArray).clone()); } else if (objArray instanceof byte[]) { return new NativeArray(copyArray((byte[])objArray)); } else if (objArray instanceof short[]) { return new NativeArray(copyArray((short[])objArray)); } else if (objArray instanceof char[]) { return new NativeArray(copyArray((char[])objArray)); } else if (objArray instanceof float[]) { return new NativeArray(copyArray((float[])objArray)); } else if (objArray instanceof boolean[]) { return new NativeArray(copyArray((boolean[])objArray)); } throw typeError("cant.convert.to.javascript.array", objArray.getClass().getName()); } private static int[] copyArray(final byte[] in) { final int[] out = new int[in.length]; for(int i = 0; i < in.length; ++i) { out[i] = in[i]; } return out; } private static int[] copyArray(final short[] in) { final int[] out = new int[in.length]; for(int i = 0; i < in.length; ++i) { out[i] = in[i]; } return out; } private static int[] copyArray(final char[] in) { final int[] out = new int[in.length]; for(int i = 0; i < in.length; ++i) { out[i] = in[i]; } return out; } private static double[] copyArray(final float[] in) { final double[] out = new double[in.length]; for(int i = 0; i < in.length; ++i) { out[i] = in[i]; } return out; } private static Object[] copyArray(final boolean[] in) { final Object[] out = new Object[in.length]; for(int i = 0; i < in.length; ++i) { out[i] = in[i]; } return out; } private static Class<?> simpleType(final String typeName) throws ClassNotFoundException { final Class<?> primClass = TypeUtilities.getPrimitiveTypeByName(typeName); return primClass != null ? primClass : Global.getThisContext().findClass(typeName); } private static Class<?> arrayType(final String typeName) throws ClassNotFoundException { return Array.newInstance(type(typeName.substring(0, typeName.length() - 2)), 0).getClass(); } /** * Returns a type object for a subclass of the specified Java class (or implementation of the specified interface) * that acts as a script-to-Java adapter for it. See {@link #type(Object, Object)} for a discussion of type objects, * and see {@link JavaAdapterFactory} for details on script-to-Java adapters. Note that you can also implement * interfaces and subclass abstract classes using {@code new} operator on a type object for an interface or abstract * class. However, to extend a non-abstract class, you will have to use this method. Example: * <pre> * var ArrayList = Java.type("java.util.ArrayList") * var ArrayListExtender = Java.extend(ArrayList) * var printSizeInvokedArrayList = new ArrayListExtender() { * size: function() { print("size invoked!"); } * } * var printAddInvokedArrayList = new ArrayListExtender() { * add: function(x, y) { * if(typeof(y) === "undefined") { * print("add(e) invoked!"); * } else { * print("add(i, e) invoked!"); * } * } * </pre> * We can see several important concepts in the above example: * <ul> * <li>Every specified list of Java types will have exactly one extender subclass in Nashorn - repeated invocations * of {@code extend} for the same list of types will yield the same extender type. It's a generic adapter that * delegates to whatever JavaScript functions its implementation object has on a per-instance basis.</li> * <li>If the Java method is overloaded (as in the above example {@code List.add()}), then your JavaScript adapter * must be prepared to deal with all overloads.</li> * <li>You can't invoke {@code super.*()} from adapters for now.</li> * <li>It is also possible to specify an ordinary JavaScript object as the last argument to {@code extend}. In that * case, it is treated as a class-level override. {@code extend} will return an extender class where all instances * will have the methods implemented by functions on that object, just as if that object were passed as the last * argument to their constructor. Example: * <pre> * var Runnable = Java.type("java.lang.Runnable") * var R1 = Java.extend(Runnable, { * run: function() { * print("R1.run() invoked!") * } * }) * var r1 = new R1 * var t = new java.lang.Thread(r1) * t.start() * t.join() * </pre> * As you can see, you don't have to pass any object when you create a new instance of {@code R1} as its * {@code run()} function was defined already when extending the class. Of course, you can still provide * instance-level overrides on these objects. The order of precedence is instance-level method, class-level method, * superclass method, or {@code UnsupportedOperationException} if the superclass method is abstract. If we continue * our previous example: * <pre> * var r2 = new R1(function() { print("r2.run() invoked!") }) * r2.run() * </pre> * We'll see it'll print {@code "r2.run() invoked!"}, thus overriding on instance-level the class-level behavior. * </li> * </ul> * @param self not used * @param types the original types. The caller must pass at least one Java type object of class {@link StaticClass} * representing either a public interface or a non-final public class with at least one public or protected * constructor. If more than one type is specified, at most one can be a class and the rest have to be interfaces. * Invoking the method twice with exactly the same types in the same order - in absence of class-level overrides - * will return the same adapter class, any reordering of types or even addition or removal of redundant types (i.e. * interfaces that other types in the list already implement/extend, or {@code java.lang.Object} in a list of types * consisting purely of interfaces) will result in a different adapter class, even though those adapter classes are * functionally identical; we deliberately don't want to incur the additional processing cost of canonicalizing type * lists. As a special case, the last argument can be a {@code ScriptObject} instead of a type. In this case, a * separate adapter class is generated - new one for each invocation - that will use the passed script object as its * implementation for all instances. Instances of such adapter classes can then be created without passing another * script object in the constructor, as the class has a class-level behavior defined by the script object. However, * you can still pass a script object (or if it's a SAM type, a function) to the constructor to provide further * instance-level overrides. * * @return a new {@link StaticClass} that represents the adapter for the original types. */ @Function(attributes = Attribute.NOT_ENUMERABLE, where = Where.CONSTRUCTOR) public static Object extend(final Object self, final Object... types) { if(types == null || types.length == 0) { throw typeError("extend.expects.at.least.one.argument"); } final int l = types.length; final int typesLen; final ScriptObject classOverrides; if(types[l - 1] instanceof ScriptObject) { classOverrides = (ScriptObject)types[l - 1]; typesLen = l - 1; if(typesLen == 0) { throw typeError("extend.expects.at.least.one.type.argument"); } } else { classOverrides = null; typesLen = l; } final Class<?>[] stypes = new Class<?>[typesLen]; try { for(int i = 0; i < typesLen; ++i) { stypes[i] = ((StaticClass)types[i]).getRepresentedClass(); } } catch(final ClassCastException e) { throw typeError("extend.expects.java.types"); } return JavaAdapterFactory.getAdapterClassFor(stypes, classOverrides); } }