nativejavaobject.java

這是一個javascript 的 interpreter是了解 web browser的好材料

                value = ((Wrapper)value).unwrap();
                if (type.isInstance(value))
                    return value;
                reportConversionError(value, type);
            }
            else if (type.isInterface() && value instanceof Callable) {
                // Try to use function as implementation of Java interface.
                //
                // XXX: Curently only instances of ScriptableObject are
                // supported since the resulting interface proxies should
                // be reused next time conversion is made and generic
                // Callable has no storage for it. Weak references can
                // address it but for now use this restriction.
                if (value instanceof ScriptableObject) {
                    ScriptableObject so = (ScriptableObject)value;
                    Object key = Kit.makeHashKeyFromPair(
                        COERCED_INTERFACE_KEY, type);
                    Object old = so.getAssociatedValue(key);
                    if (old != null) {
                        // Function was already wrapped
                        return old;
                    }
                    Context cx = Context.getContext();
                    Object glue
                        = InterfaceAdapter.create(cx, type, (Callable)value);
                    // Store for later retrival
                    glue = so.associateValue(key, glue);
                    return glue;
                }
                reportConversionError(value, type);
            } else {
                reportConversionError(value, type);
            }
            break;
        }

        return value;
    }

    private static Object coerceToNumber(Class type, Object value)
    {
        Class valueClass = value.getClass();

        // Character
        if (type == Character.TYPE || type == ScriptRuntime.CharacterClass) {
            if (valueClass == ScriptRuntime.CharacterClass) {
                return value;
            }
            return new Character((char)toInteger(value,
                                                 ScriptRuntime.CharacterClass,
                                                 Character.MIN_VALUE,
                                                 Character.MAX_VALUE));
        }

        // Double, Float
        if (type == ScriptRuntime.ObjectClass ||
            type == ScriptRuntime.DoubleClass || type == Double.TYPE) {
            return valueClass == ScriptRuntime.DoubleClass
                ? value
                : new Double(toDouble(value));
        }

        if (type == ScriptRuntime.FloatClass || type == Float.TYPE) {
            if (valueClass == ScriptRuntime.FloatClass) {
                return value;
            }
            else {
                double number = toDouble(value);
                if (Double.isInfinite(number) || Double.isNaN(number)
                    || number == 0.0) {
                    return new Float((float)number);
                }
                else {
                    double absNumber = Math.abs(number);
                    if (absNumber < Float.MIN_VALUE) {
                        return new Float((number > 0.0) ? +0.0 : -0.0);
                    }
                    else if (absNumber > Float.MAX_VALUE) {
                        return new Float((number > 0.0) ?
                                         Float.POSITIVE_INFINITY :
                                         Float.NEGATIVE_INFINITY);
                    }
                    else {
                        return new Float((float)number);
                    }
                }
            }
        }

        // Integer, Long, Short, Byte
        if (type == ScriptRuntime.IntegerClass || type == Integer.TYPE) {
            if (valueClass == ScriptRuntime.IntegerClass) {
                return value;
            }
            else {
                return new Integer((int)toInteger(value,
                                                  ScriptRuntime.IntegerClass,
                                                  Integer.MIN_VALUE,
                                                  Integer.MAX_VALUE));
            }
        }

        if (type == ScriptRuntime.LongClass || type == Long.TYPE) {
            if (valueClass == ScriptRuntime.LongClass) {
                return value;
            } else {
                /* Long values cannot be expressed exactly in doubles.
                 * We thus use the largest and smallest double value that
                 * has a value expressible as a long value. We build these
                 * numerical values from their hexidecimal representations
                 * to avoid any problems caused by attempting to parse a
                 * decimal representation.
                 */
                final double max = Double.longBitsToDouble(0x43dfffffffffffffL);
                final double min = Double.longBitsToDouble(0xc3e0000000000000L);
                return new Long(toInteger(value,
                                          ScriptRuntime.LongClass,
                                          min,
                                          max));
            }
        }

        if (type == ScriptRuntime.ShortClass || type == Short.TYPE) {
            if (valueClass == ScriptRuntime.ShortClass) {
                return value;
            }
            else {
                return new Short((short)toInteger(value,
                                                  ScriptRuntime.ShortClass,
                                                  Short.MIN_VALUE,
                                                  Short.MAX_VALUE));
            }
        }

        if (type == ScriptRuntime.ByteClass || type == Byte.TYPE) {
            if (valueClass == ScriptRuntime.ByteClass) {
                return value;
            }
            else {
                return new Byte((byte)toInteger(value,
                                                ScriptRuntime.ByteClass,
                                                Byte.MIN_VALUE,
                                                Byte.MAX_VALUE));
            }
        }

        return new Double(toDouble(value));
    }


    private static double toDouble(Object value)
    {
        if (value instanceof Number) {
            return ((Number)value).doubleValue();
        }
        else if (value instanceof String) {
            return ScriptRuntime.toNumber((String)value);
        }
        else if (value instanceof Scriptable) {
            if (value instanceof Wrapper) {
                // XXX: optimize tail-recursion?
                return toDouble(((Wrapper)value).unwrap());
            }
            else {
                return ScriptRuntime.toNumber(value);
            }
        }
        else {
            Method meth;
            try {
                meth = value.getClass().getMethod("doubleValue", 
                		                          (Class [])null);
            }
            catch (NoSuchMethodException e) {
                meth = null;
            }
            catch (SecurityException e) {
                meth = null;
            }
            if (meth != null) {
                try {
                    return ((Number)meth.invoke(value, 
                    		                    (Object [])null)).doubleValue();
                }
                catch (IllegalAccessException e) {
                    // XXX: ignore, or error message?
                    reportConversionError(value, Double.TYPE);
                }
                catch (InvocationTargetException e) {
                    // XXX: ignore, or error message?
                    reportConversionError(value, Double.TYPE);
                }
            }
            return ScriptRuntime.toNumber(value.toString());
        }
    }

    private static long toInteger(Object value, Class type,
                                  double min, double max)
    {
        double d = toDouble(value);

        if (Double.isInfinite(d) || Double.isNaN(d)) {
            // Convert to string first, for more readable message
            reportConversionError(ScriptRuntime.toString(value), type);
        }

        if (d > 0.0) {
            d = Math.floor(d);
        }
        else {
            d = Math.ceil(d);
        }

        if (d < min || d > max) {
            // Convert to string first, for more readable message
            reportConversionError(ScriptRuntime.toString(value), type);
        }
        return (long)d;
    }

    static void reportConversionError(Object value, Class type)
    {
        // It uses String.valueOf(value), not value.toString() since
        // value can be null, bug 282447.
        throw Context.reportRuntimeError2(
            "msg.conversion.not.allowed",
            String.valueOf(value),
            JavaMembers.javaSignature(type));
    }

    private void writeObject(ObjectOutputStream out)
        throws IOException
    {
        out.defaultWriteObject();

        out.writeBoolean(isAdapter);
        if (isAdapter) {
            if (adapter_writeAdapterObject == null) {
                throw new IOException();
            }
            Object[] args = { javaObject, out };
            try {
                adapter_writeAdapterObject.invoke(null, args);
            } catch (Exception ex) {
                throw new IOException();
            }
        } else {
            out.writeObject(javaObject);
        }

        if (staticType != null) {
            out.writeObject(staticType.getClass().getName());
        } else {
            out.writeObject(null);
        }
    }

    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException
    {
        in.defaultReadObject();

        isAdapter = in.readBoolean();
        if (isAdapter) {
            if (adapter_readAdapterObject == null)
                throw new ClassNotFoundException();
            Object[] args = { this, in };
            try {
                javaObject = adapter_readAdapterObject.invoke(null, args);
            } catch (Exception ex) {
                throw new IOException();
            }
        } else {
            javaObject = in.readObject();
        }

        String className = (String)in.readObject();
        if (className != null) {
            staticType = Class.forName(className);
        } else {
            staticType = null;
        }

        initMembers();
    }

    /**
     * The prototype of this object.
     */
    protected Scriptable prototype;

    /**
     * The parent scope of this object.
     */
    protected Scriptable parent;

    protected transient Object javaObject;

    protected transient Class staticType;
    protected transient JavaMembers members;
    private transient Hashtable fieldAndMethods;
    private transient boolean isAdapter;

    private static final Object COERCED_INTERFACE_KEY = new Object();
    private static Method adapter_writeAdapterObject;
    private static Method adapter_readAdapterObject;

    static {
        // Reflection in java is verbose
        Class[] sig2 = new Class[2];
        Class cl = Kit.classOrNull("org.mozilla.javascript.JavaAdapter");
        if (cl != null) {
            try {
                sig2[0] = ScriptRuntime.ObjectClass;
                sig2[1] = Kit.classOrNull("java.io.ObjectOutputStream");
                adapter_writeAdapterObject = cl.getMethod("writeAdapterObject",
                                                          sig2);

                sig2[0] = ScriptRuntime.ScriptableClass;
                sig2[1] = Kit.classOrNull("java.io.ObjectInputStream");
                adapter_readAdapterObject = cl.getMethod("readAdapterObject",
                                                         sig2);

            } catch (Exception ex) {
                adapter_writeAdapterObject = null;
                adapter_readAdapterObject = null;
            }
        }
    }

}