context.java

java中比较著名的js引擎当属mozilla开源的rhino

    /**
     * Create an array with a specified initial length.
     * <p>
     * @param scope the scope to create the object in
     * @param length the initial length (JavaScript arrays may have
     *               additional properties added dynamically).
     * @return the new array object
     */
    public final Scriptable newArray(Scriptable scope, int length)
    {
        NativeArray result = new NativeArray(length);
        ScriptRuntime.setObjectProtoAndParent(result, scope);
        return result;
    }

    /**
     * Create an array with a set of initial elements.
     *
     * @param scope the scope to create the object in.
     * @param elements the initial elements. Each object in this array
     *                 must be an acceptable JavaScript type and type
     *                 of array should be exactly Object[], not
     *                 SomeObjectSubclass[].
     * @return the new array object.
     */
    public final Scriptable newArray(Scriptable scope, Object[] elements)
    {
        if (elements.getClass().getComponentType() != ScriptRuntime.ObjectClass)
            throw new IllegalArgumentException();
        NativeArray result = new NativeArray(elements);
        ScriptRuntime.setObjectProtoAndParent(result, scope);
        return result;
    }

    /**
     * Get the elements of a JavaScript array.
     * <p>
     * If the object defines a length property convertible to double number,
     * then the number is converted Uint32 value as defined in Ecma 9.6
     * and Java array of that size is allocated.
     * The array is initialized with the values obtained by
     * calling get() on object for each value of i in [0,length-1]. If
     * there is not a defined value for a property the Undefined value
     * is used to initialize the corresponding element in the array. The
     * Java array is then returned.
     * If the object doesn't define a length property or it is not a number,
     * empty array is returned.
     * @param object the JavaScript array or array-like object
     * @return a Java array of objects
     * @since 1.4 release 2
     */
    public final Object[] getElements(Scriptable object)
    {
        return ScriptRuntime.getArrayElements(object);
    }

    /**
     * Convert the value to a JavaScript boolean value.
     * <p>
     * See ECMA 9.2.
     *
     * @param value a JavaScript value
     * @return the corresponding boolean value converted using
     *         the ECMA rules
     */
    public static boolean toBoolean(Object value)
    {
        return ScriptRuntime.toBoolean(value);
    }

    /**
     * Convert the value to a JavaScript Number value.
     * <p>
     * Returns a Java double for the JavaScript Number.
     * <p>
     * See ECMA 9.3.
     *
     * @param value a JavaScript value
     * @return the corresponding double value converted using
     *         the ECMA rules
     */
    public static double toNumber(Object value)
    {
        return ScriptRuntime.toNumber(value);
    }

    /**
     * Convert the value to a JavaScript String value.
     * <p>
     * See ECMA 9.8.
     * <p>
     * @param value a JavaScript value
     * @return the corresponding String value converted using
     *         the ECMA rules
     */
    public static String toString(Object value)
    {
        return ScriptRuntime.toString(value);
    }

    /**
     * Convert the value to an JavaScript object value.
     * <p>
     * Note that a scope must be provided to look up the constructors
     * for Number, Boolean, and String.
     * <p>
     * See ECMA 9.9.
     * <p>
     * Additionally, arbitrary Java objects and classes will be
     * wrapped in a Scriptable object with its Java fields and methods
     * reflected as JavaScript properties of the object.
     *
     * @param value any Java object
     * @param scope global scope containing constructors for Number,
     *              Boolean, and String
     * @return new JavaScript object
     */
    public static Scriptable toObject(Object value, Scriptable scope)
    {
        return ScriptRuntime.toObject(scope, value);
    }

    /**
     * @deprecated
     * @see #toObject(Object, Scriptable)
     */
    public static Scriptable toObject(Object value, Scriptable scope,
                                      Class staticType)
    {
        return ScriptRuntime.toObject(scope, value);
    }

    /**
     * Convenient method to convert java value to its closest representation
     * in JavaScript.
     * <p>
     * If value is an instance of String, Number, Boolean, Function or
     * Scriptable, it is returned as it and will be treated as the corresponding
     * JavaScript type of string, number, boolean, function and object.
     * <p>
     * Note that for Number instances during any arithmetic operation in
     * JavaScript the engine will always use the result of
     * <tt>Number.doubleValue()</tt> resulting in a precision loss if
     * the number can not fit into double.
     * <p>
     * If value is an instance of Character, it will be converted to string of
     * length 1 and its JavaScript type will be string.
     * <p>
     * The rest of values will be wrapped as LiveConnect objects
     * by calling {@link WrapFactory#wrap(Context cx, Scriptable scope,
     * Object obj, Class staticType)} as in:
     * <pre>
     *    Context cx = Context.getCurrentContext();
     *    return cx.getWrapFactory().wrap(cx, scope, value, null);
     * </pre>
     *
     * @param value any Java object
     * @param scope top scope object
     * @return value suitable to pass to any API that takes JavaScript values.
     */
    public static Object javaToJS(Object value, Scriptable scope)
    {
        if (value instanceof String || value instanceof Number
            || value instanceof Boolean || value instanceof Scriptable)
        {
            return value;
        } else if (value instanceof Character) {
            return String.valueOf(((Character)value).charValue());
        } else {
            Context cx = Context.getContext();
            return cx.getWrapFactory().wrap(cx, scope, value, null);
        }
    }

    /**
     * Convert a JavaScript value into the desired type.
     * Uses the semantics defined with LiveConnect3 and throws an
     * Illegal argument exception if the conversion cannot be performed.
     * @param value the JavaScript value to convert
     * @param desiredType the Java type to convert to. Primitive Java
     *        types are represented using the TYPE fields in the corresponding
     *        wrapper class in java.lang.
     * @return the converted value
     * @throws EvaluatorException if the conversion cannot be performed
     */
    public static Object jsToJava(Object value, Class desiredType)
        throws EvaluatorException
    {
        return NativeJavaObject.coerceTypeImpl(desiredType, value);
    }

    /**
     * @deprecated
     * @see #jsToJava(Object, Class)
     * @throws IllegalArgumentException if the conversion cannot be performed.
     *         Note that {@link #jsToJava(Object, Class)} throws
     *         {@link EvaluatorException} instead.
     */
    public static Object toType(Object value, Class desiredType)
        throws IllegalArgumentException
    {
        try {
            return jsToJava(value, desiredType);
        } catch (EvaluatorException ex) {
            IllegalArgumentException
                ex2 = new IllegalArgumentException(ex.getMessage());
            Kit.initCause(ex2, ex);
            throw ex2;
        }
    }

    /**
     * Rethrow the exception wrapping it as the script runtime exception.
     * Unless the exception is instance of {@link EcmaError} or
     * {@link EvaluatorException} it will be wrapped as
     * {@link WrappedException}, a subclass of {@link EvaluatorException}.
     * The resulting exception object always contains
     * source name and line number of script that triggered exception.
     * <p>
     * This method always throws an exception, its return value is provided
     * only for convenience to allow a usage like:
     * <pre>
     * throw Context.throwAsScriptRuntimeEx(ex);
     * </pre>
     * to indicate that code after the method is unreachable.
     * @throws EvaluatorException
     * @throws EcmaError
     */
    public static RuntimeException throwAsScriptRuntimeEx(Throwable e)
    {
        while ((e instanceof InvocationTargetException)) {
            e = ((InvocationTargetException) e).getTargetException();
        }
        // special handling of Error so scripts would not catch them
        if (e instanceof Error) {
            throw (Error)e;
        }
        if (e instanceof RhinoException) {
            throw (RhinoException)e;
        }
        throw new WrappedException(e);
    }

    /**
     * Tell whether debug information is being generated.
     * @since 1.3
     */
    public final boolean isGeneratingDebug()
    {
        return generatingDebug;
    }

    /**
     * Specify whether or not debug information should be generated.
     * <p>
     * Setting the generation of debug information on will set the
     * optimization level to zero.
     * @since 1.3
     */
    public final void setGeneratingDebug(boolean generatingDebug)
    {
        if (sealed) onSealedMutation();
        generatingDebugChanged = true;
        if (generatingDebug && getOptimizationLevel() > 0)
            setOptimizationLevel(0);
        this.generatingDebug = generatingDebug;
    }

    /**
     * Tell whether source information is being generated.
     * @since 1.3
     */
    public final boolean isGeneratingSource()
    {
        return generatingSource;
    }

    /**
     * Specify whether or not source information should be generated.
     * <p>
     * Without source information, evaluating the "toString" method
     * on JavaScript functions produces only "[native code]" for
     * the body of the function.
     * Note that code generated without source is not fully ECMA
     * conformant.
     * @since 1.3
     */
    public final void setGeneratingSource(boolean generatingSource)
    {
        if (sealed) onSealedMutation();
        this.generatingSource = generatingSource;
    }

    /**
     * Get the current optimization level.
     * <p>
     * The optimization level is expressed as an integer between -1 and
     * 9.
     * @since 1.3
     *
     */
    public final int getOptimizationLevel()
    {
        return optimizationLevel;
    }
    
    /**
     * Set the current optimization level.
     * <p>
     * The optimization level is expected to be an integer between -1 and
     * 9. Any negative values will be interpreted as -1, and any values
     * greater than 9 will be interpreted as 9.
     * An optimization level of -1 indicates that interpretive mode will
     * always be used. Levels 0 through 9 indicate that class files may
     * be generated. Higher optimization levels trade off compile time
     * performance for runtime performance.
     * The optimizer level can't be set greater than -1 if the optimizer
     * package doesn't exist at run time.
     * @param optimizationLevel an integer indicating the level of
     *        optimization to perform
     * @since 1.3
     *
     */
    public final void setOptimizationLevel(int optimizationLevel)
    {
        if (sealed) onSealedMutation();
        if (optimizationLevel == -2) {
            // To be compatible with Cocoon fork
            optimizationLevel = -1;
        }
        checkOptimizationLevel(optimizationLevel);
        if (codegenClass == null)
            optimizationLevel = -1;
        this.optimizationLevel = optimizationLevel;
    }

    public static boolean isValidOptimizationLevel(int optimizationLevel)
    {
        return -1 <= optimizationLevel && optimizationLevel <= 9;
    }

    public static void checkOptimizationLevel(int optimizationLevel)
    {
        if (isValidOptimizationLevel(optimizationLevel)) {
            return;
        }
        throw new IllegalArgumentException(
            "Optimization level outside [-1..9]: "+optimizationLevel);
    }

    /**
     * Returns the maximum stack depth (in terms of number of call frames) 
     * allowed in a single invocation of interpreter. If the set depth would be
     * exceeded, the interpreter will throw an EvaluatorException in the script.
     * Defaults to Integer.MAX_VALUE. The setting only has effect for 
     * interpreted functions (those compiled with optimization level set to -1).
     * As the interpreter doesn't use the Java stack but rather manages its own
     * stack in the heap memory, a runaway recursion in interpreted code would 
     * eventually consume all available memory and cause OutOfMemoryError 
     * instead of a StackOv