context.java

java中比较著名的js引擎当属mozilla开源的rhino

     * @return the initialized scope. The method returns the value of the scope
     *         argument if it is not null or newly allocated scope object.
     * @since 1.4R3
     */
    public ScriptableObject initStandardObjects(ScriptableObject scope,
                                                boolean sealed)
    {
        return ScriptRuntime.initStandardObjects(this, scope, sealed);
    }

    /**
     * Get the singleton object that represents the JavaScript Undefined value.
     */
    public static Object getUndefinedValue()
    {
        return Undefined.instance;
    }

    /**
     * Evaluate a JavaScript source string.
     *
     * The provided source name and line number are used for error messages
     * and for producing debug information.
     *
     * @param scope the scope to execute in
     * @param source the JavaScript source
     * @param sourceName a string describing the source, such as a filename
     * @param lineno the starting line number
     * @param securityDomain an arbitrary object that specifies security
     *        information about the origin or owner of the script. For
     *        implementations that don't care about security, this value
     *        may be null.
     * @return the result of evaluating the string
     * @see org.mozilla.javascript.SecurityController
     */
    public final Object evaluateString(Scriptable scope, String source,
                                       String sourceName, int lineno,
                                       Object securityDomain)
    {
        Script script = compileString(source, sourceName, lineno,
                                      securityDomain);
        if (script != null) {
            return script.exec(this, scope);
        } else {
            return null;
        }
    }

    /**
     * Evaluate a reader as JavaScript source.
     *
     * All characters of the reader are consumed.
     *
     * @param scope the scope to execute in
     * @param in the Reader to get JavaScript source from
     * @param sourceName a string describing the source, such as a filename
     * @param lineno the starting line number
     * @param securityDomain an arbitrary object that specifies security
     *        information about the origin or owner of the script. For
     *        implementations that don't care about security, this value
     *        may be null.
     * @return the result of evaluating the source
     *
     * @exception IOException if an IOException was generated by the Reader
     */
    public final Object evaluateReader(Scriptable scope, Reader in,
                                       String sourceName, int lineno,
                                       Object securityDomain)
        throws IOException
    {
        Script script = compileReader(scope, in, sourceName, lineno,
                                      securityDomain);
        if (script != null) {
            return script.exec(this, scope);
        } else {
            return null;
        }
    }

    /**
     * Check whether a string is ready to be compiled.
     * <p>
     * stringIsCompilableUnit is intended to support interactive compilation of
     * javascript.  If compiling the string would result in an error
     * that might be fixed by appending more source, this method
     * returns false.  In every other case, it returns true.
     * <p>
     * Interactive shells may accumulate source lines, using this
     * method after each new line is appended to check whether the
     * statement being entered is complete.
     *
     * @param source the source buffer to check
     * @return whether the source is ready for compilation
     * @since 1.4 Release 2
     */
    public final boolean stringIsCompilableUnit(String source)
    {
        boolean errorseen = false;
        CompilerEnvirons compilerEnv = new CompilerEnvirons();
        compilerEnv.initFromContext(this);
        // no source name or source text manager, because we're just
        // going to throw away the result.
        compilerEnv.setGeneratingSource(false);
        Parser p = new Parser(compilerEnv, DefaultErrorReporter.instance);
        try {
            p.parse(source, null, 1);
        } catch (EvaluatorException ee) {
            errorseen = true;
        }
        // Return false only if an error occurred as a result of reading past
        // the end of the file, i.e. if the source could be fixed by
        // appending more source.
        if (errorseen && p.eof())
            return false;
        else
            return true;
    }

    /**
     * @deprecated
     * @see #compileReader(Reader in, String sourceName, int lineno,
     *                     Object securityDomain)
     */
    public final Script compileReader(Scriptable scope, Reader in,
                                      String sourceName, int lineno,
                                      Object securityDomain)
        throws IOException
    {
        return compileReader(in, sourceName, lineno, securityDomain);
    }

    /**
     * Compiles the source in the given reader.
     * <p>
     * Returns a script that may later be executed.
     * Will consume all the source in the reader.
     *
     * @param in the input reader
     * @param sourceName a string describing the source, such as a filename
     * @param lineno the starting line number for reporting errors
     * @param securityDomain an arbitrary object that specifies security
     *        information about the origin or owner of the script. For
     *        implementations that don't care about security, this value
     *        may be null.
     * @return a script that may later be executed
     * @exception IOException if an IOException was generated by the Reader
     * @see org.mozilla.javascript.Script
     */
    public final Script compileReader(Reader in, String sourceName,
                                      int lineno, Object securityDomain)
        throws IOException
    {
        if (lineno < 0) {
            // For compatibility IllegalArgumentException can not be thrown here
            lineno = 0;
        }
        return (Script) compileImpl(null, in, null, sourceName, lineno,
                                    securityDomain, false, null, null);
    }

    /**
     * Compiles the source in the given string.
     * <p>
     * Returns a script that may later be executed.
     *
     * @param source the source string
     * @param sourceName a string describing the source, such as a filename
     * @param lineno the starting line number for reporting errors
     * @param securityDomain an arbitrary object that specifies security
     *        information about the origin or owner of the script. For
     *        implementations that don't care about security, this value
     *        may be null.
     * @return a script that may later be executed
     * @see org.mozilla.javascript.Script
     */
    public final Script compileString(String source,
                                      String sourceName, int lineno,
                                      Object securityDomain)
    {
        if (lineno < 0) {
            // For compatibility IllegalArgumentException can not be thrown here
            lineno = 0;
        }
        return compileString(source, null, null, sourceName, lineno,
                             securityDomain);
    }

    final Script compileString(String source,
                               Interpreter compiler,
                               ErrorReporter compilationErrorReporter,
                               String sourceName, int lineno,
                               Object securityDomain)
    {
        try {
            return (Script) compileImpl(null, null, source, sourceName, lineno,
                                        securityDomain, false,
                                        compiler, compilationErrorReporter);
        } catch (IOException ex) {
            // Should not happen when dealing with source as string
            throw new RuntimeException();
        }
    }

    /**
     * Compile a JavaScript function.
     * <p>
     * The function source must be a function definition as defined by
     * ECMA (e.g., "function f(a) { return a; }").
     *
     * @param scope the scope to compile relative to
     * @param source the function definition source
     * @param sourceName a string describing the source, such as a filename
     * @param lineno the starting line number
     * @param securityDomain an arbitrary object that specifies security
     *        information about the origin or owner of the script. For
     *        implementations that don't care about security, this value
     *        may be null.
     * @return a Function that may later be called
     * @see org.mozilla.javascript.Function
     */
    public final Function compileFunction(Scriptable scope, String source,
                                          String sourceName, int lineno,
                                          Object securityDomain)
    {
        return compileFunction(scope, source, null, null, sourceName, lineno,
                               securityDomain);
    }

    final Function compileFunction(Scriptable scope, String source,
                                   Interpreter compiler,
                                   ErrorReporter compilationErrorReporter,
                                   String sourceName, int lineno,
                                   Object securityDomain)
    {
        try {
            return (Function) compileImpl(scope, null, source, sourceName,
                                          lineno, securityDomain, true,
                                          compiler, compilationErrorReporter);
        }
        catch (IOException ioe) {
            // Should never happen because we just made the reader
            // from a String
            throw new RuntimeException();
        }
    }

    /**
     * Decompile the script.
     * <p>
     * The canonical source of the script is returned.
     *
     * @param script the script to decompile
     * @param indent the number of spaces to indent the result
     * @return a string representing the script source
     */
    public final String decompileScript(Script script, int indent)
    {
        NativeFunction scriptImpl = (NativeFunction) script;
        return scriptImpl.decompile(indent, 0);
    }

    /**
     * Decompile a JavaScript Function.
     * <p>
     * Decompiles a previously compiled JavaScript function object to
     * canonical source.
     * <p>
     * Returns function body of '[native code]' if no decompilation
     * information is available.
     *
     * @param fun the JavaScript function to decompile
     * @param indent the number of spaces to indent the result
     * @return a string representing the function source
     */
    public final String decompileFunction(Function fun, int indent)
    {
        if (fun instanceof BaseFunction)
            return ((BaseFunction)fun).decompile(indent, 0);
        else
            return "function " + fun.getClassName() +
                   "() {\n\t[native code]\n}\n";
    }

    /**
     * Decompile the body of a JavaScript Function.
     * <p>
     * Decompiles the body a previously compiled JavaScript Function
     * object to canonical source, omitting the function header and
     * trailing brace.
     *
     * Returns '[native code]' if no decompilation information is available.
     *
     * @param fun the JavaScript function to decompile
     * @param indent the number of spaces to indent the result
     * @return a string representing the function body source.
     */
    public final String decompileFunctionBody(Function fun, int indent)
    {
        if (fun instanceof BaseFunction) {
            BaseFunction bf = (BaseFunction)fun;
            return bf.decompile(indent, Decompiler.ONLY_BODY_FLAG);
        }
        // ALERT: not sure what the right response here is.
        return "[native code]\n";
    }

    /**
     * Create a new JavaScript object.
     *
     * Equivalent to evaluating "new Object()".
     * @param scope the scope to search for the constructor and to evaluate
     *              against
     * @return the new object
     */
    public final Scriptable newObject(Scriptable scope)
    {
        return newObject(scope, "Object", ScriptRuntime.emptyArgs);
    }

    /**
     * Create a new JavaScript object by executing the named constructor.
     *
     * The call <code>newObject(scope, "Foo")</code> is equivalent to
     * evaluating "new Foo()".
     *
     * @param scope the scope to search for the constructor and to evaluate against
     * @param constructorName the name of the constructor to call
     * @return the new object
     */
    public final Scriptable newObject(Scriptable scope, String constructorName)
    {
        return newObject(scope, constructorName, ScriptRuntime.emptyArgs);
    }

    /**
     * Creates a new JavaScript object by executing the named constructor.
     *
     * Searches <code>scope</code> for the named constructor, calls it with
     * the given arguments, and returns the result.<p>
     *
     * The code
     * <pre>
     * Object[] args = { "a", "b" };
     * newObject(scope, "Foo", args)</pre>
     * is equivalent to evaluating "new Foo('a', 'b')", assuming that the Foo
     * constructor has been defined in <code>scope</code>.
     *
     * @param scope The scope to search for the constructor and to evaluate
     *              against
     * @param constructorName the name of the constructor to call
     * @param args the array of arguments for the constructor
     * @return the new object
     */
    public final Scriptable newObject(Scriptable scope, String constructorName,
                                      Object[] args)
    {
        scope = ScriptableObject.getTopLevelScope(scope);
        Function ctor = ScriptRuntime.getExistingCtor(this, scope,
                                                      constructorName);
        if (args == null) { args = ScriptRuntime.emptyArgs; }
        return ctor.construct(this, scope, args);
    }