scriptableobject.java

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

    {
        Context cx = null;
        for (int i=0; i < 2; i++) {
            boolean tryToString;
            if (typeHint == ScriptRuntime.StringClass) {
                tryToString = (i == 0);
            } else {
                tryToString = (i == 1);
            }

            String methodName;
            Object[] args;
            if (tryToString) {
                methodName = "toString";
                args = ScriptRuntime.emptyArgs;
            } else {
                methodName = "valueOf";
                args = new Object[1];
                String hint;
                if (typeHint == null) {
                    hint = "undefined";
                } else if (typeHint == ScriptRuntime.StringClass) {
                    hint = "string";
                } else if (typeHint == ScriptRuntime.ScriptableClass) {
                    hint = "object";
                } else if (typeHint == ScriptRuntime.FunctionClass) {
                    hint = "function";
                } else if (typeHint == ScriptRuntime.BooleanClass
                           || typeHint == Boolean.TYPE)
                {
                    hint = "boolean";
                } else if (typeHint == ScriptRuntime.NumberClass ||
                         typeHint == ScriptRuntime.ByteClass ||
                         typeHint == Byte.TYPE ||
                         typeHint == ScriptRuntime.ShortClass ||
                         typeHint == Short.TYPE ||
                         typeHint == ScriptRuntime.IntegerClass ||
                         typeHint == Integer.TYPE ||
                         typeHint == ScriptRuntime.FloatClass ||
                         typeHint == Float.TYPE ||
                         typeHint == ScriptRuntime.DoubleClass ||
                         typeHint == Double.TYPE)
                {
                    hint = "number";
                } else {
                    throw Context.reportRuntimeError1(
                        "msg.invalid.type", typeHint.toString());
                }
                args[0] = hint;
            }
            Object v = getProperty(object, methodName);
            if (!(v instanceof Function))
                continue;
            Function fun = (Function) v;
            if (cx == null)
                cx = Context.getContext();
            v = fun.call(cx, fun.getParentScope(), object, args);
            if (v != null) {
                if (!(v instanceof Scriptable)) {
                    return v;
                }
                if (typeHint == ScriptRuntime.ScriptableClass
                    || typeHint == ScriptRuntime.FunctionClass)
                {
                    return v;
                }
                if (tryToString && v instanceof Wrapper) {
                    // Let a wrapped java.lang.String pass for a primitive
                    // string.
                    Object u = ((Wrapper)v).unwrap();
                    if (u instanceof String)
                        return u;
                }
            }
        }
        // fall through to error
        String arg = (typeHint == null) ? "undefined" : typeHint.getName();
        throw ScriptRuntime.typeError1("msg.default.value", arg);
    }

    /**
     * Implements the instanceof operator.
     *
     * <p>This operator has been proposed to ECMA.
     *
     * @param instance The value that appeared on the LHS of the instanceof
     *              operator
     * @return true if "this" appears in value's prototype chain
     *
     */
    public boolean hasInstance(Scriptable instance) {
        // Default for JS objects (other than Function) is to do prototype
        // chasing.  This will be overridden in NativeFunction and non-JS
        // objects.

        return ScriptRuntime.jsDelegatesTo(instance, this);
    }
    
    /**
     * Emulate the SpiderMonkey (and Firefox) feature of allowing
     * custom objects to avoid detection by normal "object detection"
     * code patterns. This is used to implement document.all.
     * See https://bugzilla.mozilla.org/show_bug.cgi?id=412247.
     * This is an analog to JOF_DETECTING from SpiderMonkey; see
     * https://bugzilla.mozilla.org/show_bug.cgi?id=248549.
     * Other than this special case, embeddings should return false.
     * @return true if this object should avoid object detection
     * @since 1.7R1
     */
    public boolean avoidObjectDetection() {
        return false;
    }

    /**
     * Custom <tt>==</tt> operator.
     * Must return {@link Scriptable#NOT_FOUND} if this object does not
     * have custom equality operator for the given value,
     * <tt>Boolean.TRUE</tt> if this object is equivalent to <tt>value</tt>,
     * <tt>Boolean.FALSE</tt> if this object is not equivalent to
     * <tt>value</tt>.
     * <p>
     * The default implementation returns Boolean.TRUE
     * if <tt>this == value</tt> or {@link Scriptable#NOT_FOUND} otherwise.
     * It indicates that by default custom equality is available only if
     * <tt>value</tt> is <tt>this</tt> in which case true is returned.
     */
    protected Object equivalentValues(Object value)
    {
        return (this == value) ? Boolean.TRUE : Scriptable.NOT_FOUND;
    }

    /**
     * Defines JavaScript objects from a Java class that implements Scriptable.
     *
     * If the given class has a method
     * <pre>
     * static void init(Context cx, Scriptable scope, boolean sealed);</pre>
     *
     * or its compatibility form
     * <pre>
     * static void init(Scriptable scope);</pre>
     *
     * then it is invoked and no further initialization is done.<p>
     *
     * However, if no such a method is found, then the class's constructors and
     * methods are used to initialize a class in the following manner.<p>
     *
     * First, the zero-parameter constructor of the class is called to
     * create the prototype. If no such constructor exists,
     * a {@link EvaluatorException} is thrown. <p>
     *
     * Next, all methods are scanned for special prefixes that indicate that they
     * have special meaning for defining JavaScript objects.
     * These special prefixes are
     * <ul>
     * <li><code>jsFunction_</code> for a JavaScript function
     * <li><code>jsStaticFunction_</code> for a JavaScript function that
     *           is a property of the constructor
     * <li><code>jsGet_</code> for a getter of a JavaScript property
     * <li><code>jsSet_</code> for a setter of a JavaScript property
     * <li><code>jsConstructor</code> for a JavaScript function that
     *           is the constructor
     * </ul><p>
     *
     * If the method's name begins with "jsFunction_", a JavaScript function
     * is created with a name formed from the rest of the Java method name
     * following "jsFunction_". So a Java method named "jsFunction_foo" will
     * define a JavaScript method "foo". Calling this JavaScript function
     * will cause the Java method to be called. The parameters of the method
     * must be of number and types as defined by the FunctionObject class.
     * The JavaScript function is then added as a property
     * of the prototype. <p>
     *
     * If the method's name begins with "jsStaticFunction_", it is handled
     * similarly except that the resulting JavaScript function is added as a
     * property of the constructor object. The Java method must be static.
     *
     * If the method's name begins with "jsGet_" or "jsSet_", the method is
     * considered to define a property. Accesses to the defined property
     * will result in calls to these getter and setter methods. If no
     * setter is defined, the property is defined as READONLY.<p>
     *
     * If the method's name is "jsConstructor", the method is
     * considered to define the body of the constructor. Only one
     * method of this name may be defined.
     * If no method is found that can serve as constructor, a Java
     * constructor will be selected to serve as the JavaScript
     * constructor in the following manner. If the class has only one
     * Java constructor, that constructor is used to define
     * the JavaScript constructor. If the the class has two constructors,
     * one must be the zero-argument constructor (otherwise an
     * {@link EvaluatorException} would have already been thrown
     * when the prototype was to be created). In this case
     * the Java constructor with one or more parameters will be used
     * to define the JavaScript constructor. If the class has three
     * or more constructors, an {@link EvaluatorException}
     * will be thrown.<p>
     *
     * Finally, if there is a method
     * <pre>
     * static void finishInit(Scriptable scope, FunctionObject constructor,
     *                        Scriptable prototype)</pre>
     *
     * it will be called to finish any initialization. The <code>scope</code>
     * argument will be passed, along with the newly created constructor and
     * the newly created prototype.<p>
     *
     * @param scope The scope in which to define the constructor.
     * @param clazz The Java class to use to define the JavaScript objects
     *              and properties.
     * @exception IllegalAccessException if access is not available
     *            to a reflected class member
     * @exception InstantiationException if unable to instantiate
     *            the named class
     * @exception InvocationTargetException if an exception is thrown
     *            during execution of methods of the named class
     * @see org.mozilla.javascript.Function
     * @see org.mozilla.javascript.FunctionObject
     * @see org.mozilla.javascript.ScriptableObject#READONLY
     * @see org.mozilla.javascript.ScriptableObject
     *      #defineProperty(String, Class, int)
     */
    public static void defineClass(Scriptable scope, Class clazz)
        throws IllegalAccessException, InstantiationException,
               InvocationTargetException
    {
        defineClass(scope, clazz, false, false);
    }

    /**
     * Defines JavaScript objects from a Java class, optionally
     * allowing sealing.
     *
     * Similar to <code>defineClass(Scriptable scope, Class clazz)</code>
     * except that sealing is allowed. An object that is sealed cannot have
     * properties added or removed. Note that sealing is not allowed in
     * the current ECMA/ISO language specification, but is likely for
     * the next version.
     *
     * @param scope The scope in which to define the constructor.
     * @param clazz The Java class to use to define the JavaScript objects
     *              and properties. The class must implement Scriptable.
     * @param sealed Whether or not to create sealed standard objects that
     *               cannot be modified.
     * @exception IllegalAccessException if access is not available
     *            to a reflected class member
     * @exception InstantiationException if unable to instantiate
     *            the named class
     * @exception InvocationTargetException if an exception is thrown
     *            during execution of methods of the named class
     * @since 1.4R3
     */
    public static void defineClass(Scriptable scope, Class clazz,
                                   boolean sealed)
        throws IllegalAccessException, InstantiationException,
               InvocationTargetException
    {
        defineClass(scope, clazz, sealed, false);
    }

    /**
     * Defines JavaScript objects from a Java class, optionally
     * allowing sealing and mapping of Java inheritance to JavaScript
     * prototype-based inheritance.
     *
     * Similar to <code>defineClass(Scriptable scope, Class clazz)</code>
     * except that sealing and inheritance mapping are allowed. An object
     * that is sealed cannot have properties added or removed. Note that
     * sealing is not allowed in the current ECMA/ISO language specification,
     * but is likely for the next version.
     *
     * @param scope The scope in which to define the constructor.
     * @param clazz The Java class to use to define the JavaScript objects
     *              and properties. The class must implement Scriptable.
     * @param sealed Whether or not to create sealed standard objects that
     *               cannot be modified.
     * @param mapInheritance Whether or not to map Java inheritance to
     *                       JavaScript prototype-based inheritance.
     * @return the class name for the prototype of the specified class
     * @exception IllegalAccessException if access is not available
     *            to a reflected class member
     * @exception InstantiationException if unable to instantiate
     *            the named class
     * @exception InvocationTargetException if an exception is thrown
     *            during execution of methods of the named class
     * @since 1.6R2
     */
    public static String defineClass(Scriptable scope, Class clazz,
                                     boolean sealed, boolean mapInheritance)
        throws IllegalAccessException, InstantiationException,
               InvocationTargetException
    {
        BaseFunction ctor = buildClassCtor(scope, clazz, sealed,
                                           mapInheritance);
        if (ctor == null)
            return null;
        String name = ctor.getClassPrototype().getClassName();
        defineProperty(scope, name, ctor, ScriptableObject.DONTENUM);
        return name;
    }

    static BaseFunction buildClassCtor(Scriptable scope, Class clazz,
                                       boolean sealed,
                                       boolean mapInheritance)
        throws IllegalAccessException, InstantiationException,
               InvocationTargetException
    {
        Method[] methods = FunctionObject.getMethodList(clazz);
        for (int i=0; i < methods.length; i++) {
            Method method = methods[i];
            if (!method.getName().equals("init"))
                continue;
            Class[] parmTypes = method.getParameterTypes();
            if (parmTypes.length == 3 &&
                parmTypes[0] == ScriptRuntime.ContextClass &&
                parmTypes[1] == ScriptRuntime.ScriptableClass &&
                parmTypes[2] == Boolean.TYPE &&
                Modifier.isStatic(method.getModifiers()))
            {
                Object args[] = { Context.getContext(), scope,
                                  sealed ? Boolean.TRUE : Boolean.FALSE };
                method.invoke(null, args);
                return null;
            }
            if (parmTypes.length == 1 &&
                parmTypes[0] == ScriptRuntime.ScriptableClass &&
                Modifier.isStatic(method.getModifiers()))
            {
                Object args[] = { scope };
                method.invoke(null, args);
                return null;
            }

        }

        // If we got here, there isn't an "init" method with the right
        // parameter types.

        Constructor[] ctors = clazz.getConstructors();
        Constructor protoCtor = null;
        for (int i=0; i < ctors.length; i++) {
            if (ctors[i].getParameterTypes().length == 0) {
                protoCtor = ctors[i];
                break;
            }
        }
        if (protoCtor == null) {
            throw Context.reportRuntimeError1(