Java example source code file (JSONFunctions.java)

This example Java source code file (JSONFunctions.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

callable, globalobject, jsonfunctions, jsonparser, literalnode, methodhandle, node, object, objectnode, runtimeexception, scriptfunction, scriptobject, string, threading, threads, unarynode, util

The JSONFunctions.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.runtime;

import java.lang.invoke.MethodHandle;
import java.util.Iterator;
import java.util.concurrent.Callable;
import jdk.nashorn.internal.ir.LiteralNode;
import jdk.nashorn.internal.ir.Node;
import jdk.nashorn.internal.ir.ObjectNode;
import jdk.nashorn.internal.ir.PropertyNode;
import jdk.nashorn.internal.ir.UnaryNode;
import jdk.nashorn.internal.parser.JSONParser;
import jdk.nashorn.internal.parser.TokenType;
import jdk.nashorn.internal.runtime.arrays.ArrayIndex;
import jdk.nashorn.internal.runtime.linker.Bootstrap;

/**
 * Utilities used by "JSON" object implementation.
 */
public final class JSONFunctions {
    private JSONFunctions() {}

    private static final Object REVIVER_INVOKER = new Object();

    private static MethodHandle getREVIVER_INVOKER() {
        return ((GlobalObject)Context.getGlobal()).getDynamicInvoker(REVIVER_INVOKER,
                new Callable<MethodHandle>() {
                    @Override
                    public MethodHandle call() {
                        return Bootstrap.createDynamicInvoker("dyn:call", Object.class,
                            ScriptFunction.class, ScriptObject.class, String.class, Object.class);
                    }
                });
    }

    /**
     * Returns JSON-compatible quoted version of the given string.
     *
     * @param str String to be quoted
     * @return JSON-compatible quoted string
     */
    public static String quote(final String str) {
        return JSONParser.quote(str);
    }

    /**
     * Parses the given JSON text string and returns object representation.
     *
     * @param text JSON text to be parsed
     * @param reviver  optional value: function that takes two parameters (key, value)
     * @return Object representation of JSON text given
     */
    public static Object parse(final Object text, final Object reviver) {
        final String     str     = JSType.toString(text);
        final JSONParser parser  = new JSONParser(
                new Source("<json>", str),
                new Context.ThrowErrorManager());

        Node node;

        try {
            node = parser.parse();
        } catch (final ParserException e) {
            throw ECMAErrors.syntaxError(e, "invalid.json", e.getMessage());
        }

        final ScriptObject global = Context.getGlobalTrusted();
        Object unfiltered = convertNode(global, node);
        return applyReviver(global, unfiltered, reviver);
    }

    // -- Internals only below this point

    // parse helpers

    // apply 'reviver' function if available
    private static Object applyReviver(final ScriptObject global, final Object unfiltered, final Object reviver) {
        if (reviver instanceof ScriptFunction) {
            assert global instanceof GlobalObject;
            final ScriptObject root = ((GlobalObject)global).newObject();
            root.addOwnProperty("", Property.WRITABLE_ENUMERABLE_CONFIGURABLE, unfiltered);
            return walk(root, "", (ScriptFunction)reviver);
        }
        return unfiltered;
    }

    // This is the abstract "Walk" operation from the spec.
    private static Object walk(final ScriptObject holder, final Object name, final ScriptFunction reviver) {
        final Object val = holder.get(name);
        if (val instanceof ScriptObject) {
            final ScriptObject     valueObj = (ScriptObject)val;
            final Iterator<String> iter     = valueObj.propertyIterator();

            while (iter.hasNext()) {
                final String key        = iter.next();
                final Object newElement = walk(valueObj, key, reviver);

                if (newElement == ScriptRuntime.UNDEFINED) {
                    valueObj.delete(key, false);
                } else {
                    setPropertyValue(valueObj, key, newElement, false);
                }
            }
        }

        try {
             // Object.class, ScriptFunction.class, ScriptObject.class, String.class, Object.class);
             return getREVIVER_INVOKER().invokeExact(reviver, holder, JSType.toString(name), val);
        } catch(Error|RuntimeException t) {
            throw t;
        } catch(final Throwable t) {
            throw new RuntimeException(t);
        }
    }

    // Converts IR node to runtime value
    private static Object convertNode(final ScriptObject global, final Node node) {
        assert global instanceof GlobalObject;

        if (node instanceof LiteralNode) {
            // check for array literal
            if (node.tokenType() == TokenType.ARRAY) {
                assert node instanceof LiteralNode.ArrayLiteralNode;
                final Node[] elements = ((LiteralNode.ArrayLiteralNode)node).getValue();

                // NOTE: We cannot use LiteralNode.isNumericArray() here as that
                // method uses symbols of element nodes. Since we don't do lower
                // pass, there won't be any symbols!
                if (isNumericArray(elements)) {
                    final double[] values = new double[elements.length];
                    int   index = 0;

                    for (final Node elem : elements) {
                        values[index++] = JSType.toNumber(convertNode(global, elem));
                    }
                    return ((GlobalObject)global).wrapAsObject(values);
                }

                final Object[] values = new Object[elements.length];
                int   index = 0;

                for (final Node elem : elements) {
                    values[index++] = convertNode(global, elem);
                }

                return ((GlobalObject)global).wrapAsObject(values);
            }

            return ((LiteralNode<?>)node).getValue();

        } else if (node instanceof ObjectNode) {
            final ObjectNode   objNode  = (ObjectNode) node;
            final ScriptObject object   = ((GlobalObject)global).newObject();

            for (final PropertyNode pNode: objNode.getElements()) {
                final Node         valueNode = pNode.getValue();

                final String name = pNode.getKeyName();
                final Object value = convertNode(global, valueNode);
                setPropertyValue(object, name, value, false);
            }

            return object;
        } else if (node instanceof UnaryNode) {
            // UnaryNode used only to represent negative number JSON value
            final UnaryNode unaryNode = (UnaryNode)node;
            return -((LiteralNode<?>)unaryNode.rhs()).getNumber();
        } else {
            return null;
        }
    }

    // add a new property if does not exist already, or else set old property
    private static void setPropertyValue(final ScriptObject sobj, final String name, final Object value, final boolean strict) {
        final int index = ArrayIndex.getArrayIndex(name);
        if (ArrayIndex.isValidArrayIndex(index)) {
            // array index key
            sobj.defineOwnProperty(index, value);
        } else if (sobj.getMap().findProperty(name) != null) {
            // pre-existing non-inherited property, call set
            sobj.set(name, value, strict);
        } else {
            // add new property
            sobj.addOwnProperty(name, Property.WRITABLE_ENUMERABLE_CONFIGURABLE, value);
        }
    }

    // does the given IR node represent a numeric array?
    private static boolean isNumericArray(final Node[] values) {
        for (final Node node : values) {
            if (node instanceof LiteralNode && ((LiteralNode<?>)node).getValue() instanceof Number) {
                continue;
            }
            return false;
        }
        return true;
    }
}