Java example source code file (NativeFunction.java)

This example Java source code file (NativeFunction.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

assertionerror, function, jsobject, list, nativefunction, object, parserexception, scriptfunction, scriptobject, source, string, stringbuilder, suppresswarnings, undefined, util

The NativeFunction.java Java example source code

/*
 * 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.util.List;

import jdk.nashorn.api.scripting.JSObject;
import jdk.nashorn.internal.objects.annotations.Attribute;
import jdk.nashorn.internal.objects.annotations.Constructor;
import jdk.nashorn.internal.objects.annotations.Function;
import jdk.nashorn.internal.objects.annotations.ScriptClass;
import jdk.nashorn.internal.parser.Parser;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.ParserException;
import jdk.nashorn.internal.runtime.PropertyMap;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.ScriptRuntime;
import jdk.nashorn.internal.runtime.Source;

/**
 * ECMA 15.3 Function Objects
 *
 * Note: instances of this class are never created. This class is not even a
 * subclass of ScriptObject. But, we use this class to generate prototype and
 * constructor for "Function".
 */
@ScriptClass("Function")
public final class NativeFunction {

    // initialized by nasgen
    @SuppressWarnings("unused")
    private static PropertyMap $nasgenmap$;

    // do *not* create me!
    private NativeFunction() {
        throw new UnsupportedOperationException();
    }

    /**
     * ECMA 15.3.4.2 Function.prototype.toString ( )
     *
     * @param self self reference
     * @return string representation of Function
     */
    @Function(attributes = Attribute.NOT_ENUMERABLE)
    public static Object toString(final Object self) {
        if (!(self instanceof ScriptFunction)) {
            throw typeError("not.a.function", ScriptRuntime.safeToString(self));
        }
        return ((ScriptFunction)self).toSource();
    }

    /**
     * ECMA 15.3.4.3 Function.prototype.apply (thisArg, argArray)
     *
     * @param self   self reference
     * @param thiz   {@code this} arg for apply
     * @param array  array of argument for apply
     * @return result of apply
     */
    @Function(attributes = Attribute.NOT_ENUMERABLE)
    public static Object apply(final Object self, final Object thiz, final Object array) {
        if (!(self instanceof ScriptFunction) && !(self instanceof JSObject)) {
            throw typeError("not.a.function", ScriptRuntime.safeToString(self));
        }

        Object[] args = null;

        if (array instanceof ScriptObject) {
            // look for array-like object
            final ScriptObject sobj = (ScriptObject)array;
            final Object       len  = sobj.getLength();
            final int n = (int)JSType.toUint32(len);

            args = new Object[n];
            for (int i = 0; i < args.length; i++) {
                args[i] = sobj.get(i);
            }
        } else if (array instanceof Object[]) {
            args = (Object[])array;
        } else if (array instanceof List) {
            final List<?> list = (List)array;
            list.toArray(args = new Object[list.size()]);
        } else if (array == null || array == UNDEFINED) {
            args = ScriptRuntime.EMPTY_ARRAY;
        } else if (array instanceof JSObject) {
            // look for array-like JSObject object
            final JSObject jsObj = (JSObject)array;
            final Object       len  = jsObj.hasMember("length")? jsObj.getMember("length") : Integer.valueOf(0);
            final int n = (int)JSType.toUint32(len);

            args = new Object[n];
            for (int i = 0; i < args.length; i++) {
                args[i] = jsObj.hasSlot(i)? jsObj.getSlot(i) : UNDEFINED;
            }
        } else {
            throw typeError("function.apply.expects.array");
        }

        if (self instanceof ScriptFunction) {
            return ScriptRuntime.apply((ScriptFunction)self, thiz, args);
        } else if (self instanceof JSObject) {
            return ((JSObject)self).call(thiz, args);
        }

        throw new AssertionError("should not reach here");
    }

    /**
     * ECMA 15.3.4.4 Function.prototype.call (thisArg [ , arg1 [ , arg2, ... ] ] )
     *
     * @param self self reference
     * @param args arguments for call
     * @return result of call
     */
    @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1)
    public static Object call(final Object self, final Object... args) {
        if (!(self instanceof ScriptFunction) && !(self instanceof JSObject)) {
            throw typeError("not.a.function", ScriptRuntime.safeToString(self));
        }

        Object thiz = (args.length == 0) ? UNDEFINED : args[0];
        Object[] arguments;

        if (args.length > 1) {
            arguments = new Object[args.length - 1];
            System.arraycopy(args, 1, arguments, 0, arguments.length);
        } else {
            arguments = ScriptRuntime.EMPTY_ARRAY;
        }

        if (self instanceof ScriptFunction) {
            return ScriptRuntime.apply((ScriptFunction)self, thiz, arguments);
        } else if (self instanceof JSObject) {
            return ((JSObject)self).call(thiz, arguments);
        }

        throw new AssertionError("should not reach here");
    }

    /**
     * ECMA 15.3.4.5 Function.prototype.bind (thisArg [, arg1 [, arg2, ...]])
     *
     * @param self self reference
     * @param args arguments for bind
     * @return function with bound arguments
     */
    @Function(attributes = Attribute.NOT_ENUMERABLE, arity = 1)
    public static Object bind(final Object self, final Object... args) {
        if (!(self instanceof ScriptFunction)) {
            throw typeError("not.a.function", ScriptRuntime.safeToString(self));
        }

        final Object thiz = (args.length == 0) ? UNDEFINED : args[0];

        Object[] arguments;
        if (args.length > 1) {
            arguments = new Object[args.length - 1];
            System.arraycopy(args, 1, arguments, 0, arguments.length);
        } else {
            arguments = ScriptRuntime.EMPTY_ARRAY;
        }

        return ((ScriptFunctionImpl)self).makeBoundFunction(thiz, arguments);
    }

    /**
     * Nashorn extension: Function.prototype.toSource
     *
     * @param self self reference
     * @return source for function
     */
    @Function(attributes = Attribute.NOT_ENUMERABLE)
    public static Object toSource(final Object self) {
        if (!(self instanceof ScriptFunction)) {
            throw typeError("not.a.function", ScriptRuntime.safeToString(self));
        }
        return ((ScriptFunction)self).toSource();
    }

    /**
     * ECMA 15.3.2.1 new Function (p1, p2, ... , pn, body)
     *
     * Constructor
     *
     * @param newObj is the new operator used for constructing this function
     * @param self   self reference
     * @param args   arguments
     * @return new NativeFunction
     */
    @Constructor(arity = 1)
    public static Object function(final boolean newObj, final Object self, final Object... args) {
        final StringBuilder sb = new StringBuilder();

        sb.append("(function (");
        final String funcBody;
        if (args.length > 0) {
            final StringBuilder paramListBuf = new StringBuilder();
            for (int i = 0; i < args.length - 1; i++) {
                paramListBuf.append(JSType.toString(args[i]));
                if (i < args.length - 2) {
                    paramListBuf.append(",");
                }
            }

            // now convert function body to a string
            funcBody = JSType.toString(args[args.length - 1]);

            final String paramList = paramListBuf.toString();
            if (! paramList.isEmpty()) {
                checkFunctionParameters(paramList);
                sb.append(paramList);
            }
        } else {
            funcBody = null;
        }

        sb.append(") {\n");
        if (args.length > 0) {
            checkFunctionBody(funcBody);
            sb.append(funcBody);
            sb.append('\n');
        }
        sb.append("})");

        final Global global = Global.instance();

        return Global.directEval(global, sb.toString(), global, "<function>", global.isStrictContext());
    }

    private static void checkFunctionParameters(final String params) {
        final Source src = new Source("<function>", params);
        final Parser parser = new Parser(Global.getEnv(), src, new Context.ThrowErrorManager());
        try {
            parser.parseFormalParameterList();
        } catch (final ParserException pe) {
            pe.throwAsEcmaException();
        }
    }

    private static void checkFunctionBody(final String funcBody) {
        final Source src = new Source("<function>", funcBody);
        final Parser parser = new Parser(Global.getEnv(), src, new Context.ThrowErrorManager());
        try {
            parser.parseFunctionBody();
        } catch (final ParserException pe) {
            pe.throwAsEcmaException();
        }
    }
}