@Override
    protected StateFactory init(ExpressionExecutor[] attributeExpressionExecutors, ConfigReader configReader,
                                SiddhiQueryContext siddhiQueryContext) {
        if (attributeExpressionExecutors.length != 0) {
            throw new SiddhiAppValidationException("Invalid no of arguments passed to eventTimestamp() function, " +
                    "required 0 parameters, but found " +
                    attributeExpressionExecutors.length);
        }
        timestampGenerator = siddhiQueryContext.getSiddhiAppContext().getTimestampGenerator();
        return null;
    }
Executor class for getting Siddhi application timestamp.
modules/siddhi-core/src/main/java/io/siddhi/core/executor/function/CurrentTimeMillisFunctionExecutor.java