functionobject.java

java中比较著名的js引擎当属mozilla开源的rhino

            Method method = methods[i];
            if (method != null && name.equals(method.getName())) {
                if (found != null) {
                    throw Context.reportRuntimeError2(
                        "msg.no.overload", name,
                        method.getDeclaringClass().getName());
                }
                found = method;
            }
        }
        return found;
    }

    /**
     * Returns all public methods declared by the specified class. This excludes
     * inherited methods.
     *
     * @param clazz the class from which to pull public declared methods
     * @return the public methods declared in the specified class
     * @see Class#getDeclaredMethods()
     */
    static Method[] getMethodList(Class clazz) {
        Method[] methods = null;
        try {
            // getDeclaredMethods may be rejected by the security manager
            // but getMethods is more expensive
            if (!sawSecurityException)
                methods = clazz.getDeclaredMethods();
        } catch (SecurityException e) {
            // If we get an exception once, give up on getDeclaredMethods
            sawSecurityException = true;
        }
        if (methods == null) {
            methods = clazz.getMethods();
        }
        int count = 0;
        for (int i=0; i < methods.length; i++) {
            if (sawSecurityException
                ? methods[i].getDeclaringClass() != clazz
                : !Modifier.isPublic(methods[i].getModifiers()))
            {
                methods[i] = null;
            } else {
                count++;
            }
        }
        Method[] result = new Method[count];
        int j=0;
        for (int i=0; i < methods.length; i++) {
            if (methods[i] != null)
                result[j++] = methods[i];
        }
        return result;
    }

    /**
     * Define this function as a JavaScript constructor.
     * <p>
     * Sets up the "prototype" and "constructor" properties. Also
     * calls setParent and setPrototype with appropriate values.
     * Then adds the function object as a property of the given scope, using
     *      <code>prototype.getClassName()</code>
     * as the name of the property.
     *
     * @param scope the scope in which to define the constructor (typically
     *              the global object)
     * @param prototype the prototype object
     * @see org.mozilla.javascript.Scriptable#setParentScope
     * @see org.mozilla.javascript.Scriptable#setPrototype
     * @see org.mozilla.javascript.Scriptable#getClassName
     */
    public void addAsConstructor(Scriptable scope, Scriptable prototype)
    {
        ScriptRuntime.setFunctionProtoAndParent(this, scope);
        setImmunePrototypeProperty(prototype);

        prototype.setParentScope(this);

        final int attr = ScriptableObject.DONTENUM  |
                         ScriptableObject.PERMANENT |
                         ScriptableObject.READONLY;
        defineProperty(prototype, "constructor", this, attr);

        String name = prototype.getClassName();
        defineProperty(scope, name, this, ScriptableObject.DONTENUM);

        setParentScope(scope);
    }

    /**
     * @deprecated Use {@link #getTypeTag(Class)}
     * and {@link #convertArg(Context, Scriptable, Object, int)}
     * for type convertion.
     */
    public static Object convertArg(Context cx, Scriptable scope,
                                    Object arg, Class desired)
    {
        int tag = getTypeTag(desired);
        if (tag == JAVA_UNSUPPORTED_TYPE) {
            throw Context.reportRuntimeError1
                ("msg.cant.convert", desired.getName());
        }
        return convertArg(cx, scope, arg, tag);
    }

    /**
     * Performs conversions on argument types if needed and
     * invokes the underlying Java method or constructor.
     * <p>
     * Implements Function.call.
     *
     * @see org.mozilla.javascript.Function#call(
     *          Context, Scriptable, Scriptable, Object[])
     */
    public Object call(Context cx, Scriptable scope, Scriptable thisObj,
                       Object[] args)
    {
        Object result;
        boolean checkMethodResult = false;

        if (parmsLength < 0) {
            if (parmsLength == VARARGS_METHOD) {
                Object[] invokeArgs = { cx, thisObj, args, this };
                result = member.invoke(null, invokeArgs);
                checkMethodResult = true;
            } else {
                boolean inNewExpr = (thisObj == null);
                Boolean b = inNewExpr ? Boolean.TRUE : Boolean.FALSE;
                Object[] invokeArgs = { cx, args, this, b };
                result = (member.isCtor())
                         ? member.newInstance(invokeArgs)
                         : member.invoke(null, invokeArgs);
            }

        } else {
            if (!isStatic) {
                Class clazz = member.getDeclaringClass();
                if (!clazz.isInstance(thisObj)) {
                    boolean compatible = false;
                    if (thisObj == scope) {
                        Scriptable parentScope = getParentScope();
                        if (scope != parentScope) {
                            // Call with dynamic scope for standalone function,
                            // use parentScope as thisObj
                            compatible = clazz.isInstance(parentScope);
                            if (compatible) {
                                thisObj = parentScope;
                            }
                        }
                    }
                    if (!compatible) {
                        // Couldn't find an object to call this on.
                        throw ScriptRuntime.typeError1("msg.incompat.call",
                                                       functionName);
                    }
                }
            }

            Object[] invokeArgs;
            if (parmsLength == args.length) {
                // Do not allocate new argument array if java arguments are
                // the same as the original js ones.
                invokeArgs = args;
                for (int i = 0; i != parmsLength; ++i) {
                    Object arg = args[i];
                    Object converted = convertArg(cx, scope, arg, typeTags[i]);
                    if (arg != converted) {
                        if (invokeArgs == args) {
                            invokeArgs = (Object[])args.clone();
                        }
                        invokeArgs[i] = converted;
                    }
                }
            } else if (parmsLength == 0) {
                invokeArgs = ScriptRuntime.emptyArgs;
            } else {
                invokeArgs = new Object[parmsLength];
                for (int i = 0; i != parmsLength; ++i) {
                    Object arg = (i < args.length)
                                 ? args[i]
                                 : Undefined.instance;
                    invokeArgs[i] = convertArg(cx, scope, arg, typeTags[i]);
                }
            }

            if (member.isMethod()) {
                result = member.invoke(thisObj, invokeArgs);
                checkMethodResult = true;
            } else {
                result = member.newInstance(invokeArgs);
            }

        }

        if (checkMethodResult) {
            if (hasVoidReturn) {
                result = Undefined.instance;
            } else if (returnTypeTag == JAVA_UNSUPPORTED_TYPE) {
                result = cx.getWrapFactory().wrap(cx, scope, result, null);
            }
            // XXX: the code assumes that if returnTypeTag == JAVA_OBJECT_TYPE
            // then the Java method did a proper job of converting the
            // result to JS primitive or Scriptable to avoid
            // potentially costly Context.javaToJS call.
        }

        return result;
    }

    /**
     * Return new {@link Scriptable} instance using the default
     * constructor for the class of the underlying Java method.
     * Return null to indicate that the call method should be used to create
     * new objects.
     */
    public Scriptable createObject(Context cx, Scriptable scope) {
        if (member.isCtor() || parmsLength == VARARGS_CTOR) {
            return null;
        }
        Scriptable result;
        try {
            result = (Scriptable) member.getDeclaringClass().newInstance();
        } catch (Exception ex) {
            throw Context.throwAsScriptRuntimeEx(ex);
        }

        result.setPrototype(getClassPrototype());
        result.setParentScope(getParentScope());
        return result;
    }

    boolean isVarArgsMethod() {
        return parmsLength == VARARGS_METHOD;
    }

    boolean isVarArgsConstructor() {
        return parmsLength == VARARGS_CTOR;
    }

    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException
    {
        in.defaultReadObject();
        if (parmsLength > 0) {
            Class[] types = member.argTypes;
            typeTags = new byte[parmsLength];
            for (int i = 0; i != parmsLength; ++i) {
                typeTags[i] = (byte)getTypeTag(types[i]);
            }
        }
        if (member.isMethod()) {
            Method method = member.method();
            Class returnType = method.getReturnType();
            if (returnType == Void.TYPE) {
                hasVoidReturn = true;
            } else {
                returnTypeTag = getTypeTag(returnType);
            }
        }
    }

    private static final short VARARGS_METHOD = -1;
    private static final short VARARGS_CTOR =   -2;

    private static boolean sawSecurityException;

    public static final int JAVA_UNSUPPORTED_TYPE = 0;
    public static final int JAVA_STRING_TYPE      = 1;
    public static final int JAVA_INT_TYPE         = 2;
    public static final int JAVA_BOOLEAN_TYPE     = 3;
    public static final int JAVA_DOUBLE_TYPE      = 4;
    public static final int JAVA_SCRIPTABLE_TYPE  = 5;
    public static final int JAVA_OBJECT_TYPE      = 6;

    MemberBox member;
    private String functionName;
    private transient byte[] typeTags;
    private int parmsLength;
    private transient boolean hasVoidReturn;
    private transient int returnTypeTag;
    private boolean isStatic;
}