Using Rhino instead of ScriptEngine to run Javascr

问题:

Based on the discussion converting string representation of unknown date-format to Date in java, I want to use the JavaScript Date function in my App-Engine project. However, ScriptEngine does not work on App-Engine. So I need a little help converting to Rhino. Here is the ScriptEngine code I need to convert:

ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine engine = scriptEngineManager.getEngineByName("JavaScript");
String script = "var date = new Date('" + dateInUnknownFormat + "'); var timestamp = date.getTime();";
engine.eval(script);
long timestamp = ((Double) engine.get("timestamp")).longValue();

The following has not worked

private static long parseDateUsingRhino(String dateInUnknownFormat){
    Context mozillaJsContext = Context.enter();
    Scriptable scope = mozillaJsContext.initStandardObjects();
    String script = "var date = new Date('" + dateInUnknownFormat + "'); var timestamp = date.getTime();";
    Object obj = mozillaJsContext.evaluateString( scope, script, "TestScript", 1, null );
    Double timeDouble = Double.parseDouble((String) obj);
    long timestamp = timeDouble.longValue();
    return  timestamp;
}

and I have already replaced "TestScript" with null and "".

回答1:

In the script that is executed by the JavaScript engine, you just need to calculate the value you want using new Date(dateString).getTime() (you could also use "var date = new Date(dateString); date.getTime()";). You should not store the result inside a variable.

I also made two additions to your method:

• To convert the result of the evaluation to a String, you should use Context.toString(obj). Since here, the result is actually a number, we can use directly Context.toNumber(obj), which returns a double, and cast it to long.
• I added a finally block which exits from the Context.

Working code:

private static long parseDateUsingRhino(String dateInUnknownFormat) {
    Context mozillaJsContext = Context.enter();
    try {
        Scriptable scope = mozillaJsContext.initStandardObjects();
        String script = "new Date('" + dateInUnknownFormat + "').getTime()";
        Object obj = mozillaJsContext.evaluateString(scope, script, "TestScript", 1, null);
        return (long) Context.toNumber(obj);
    } finally {
        Context.exit();
    }
}

Sample:

System.out.println(parseDateUsingRhino("2015-10-25T15:06:42.000Z")); // prints 1445785602000

Side note: this was tested with Rhino 1.7.7.

回答2:

You should try it first like this and see if it works:

private static long parseDateUsingRhino(String dateInUnknownFormat){
        Context mozillaJsContext = Context.enter();
        Scriptable scope = mozillaJsContext.initStandardObjects();
        String script = "var date = new Date().getTime();";
        Object result = mozillaJsContext.evaluateString( scope, script, "", 1, null );
        return Long.valueOf(Context.toString(result));
    }

And according to this all you need to do next is pass the dateInUnknownFormat variable like so, no java string concatenation required (the context is smart enough to probably consider the java method's accessible variables as global variables in the javascript scope):

String script = "var date = new Date(dateInUnknownFormat).getTime();";