hi, could you please provide a simple example strategy which is trading on customized bars of 1 sec basing on an indicator. thank you

See:
https://www.dukascopy.com/wiki/#Chart_feeds/Feed_history,_indicator_calculation_and_chart_opening

ok thank you for the link. i have seen that already and tried to implement it but i do not yet understand it.

all this feed stuff is put in the onStart method. what will be the Period in the onBar method then?

i was hoping it would be possible to get the Period under onBar defined to 1 sec.

Simply modify the strategy by adding another feed to the list i.e.:

CANDLESTICKS_1_SEC(new TimePeriodAggregationFeedDescriptor(Instrument.EURUSD, Period.ONE_SEC, OfferSide.ASK, Filter.NO_FILTER));

And then select it in parameters dialog on strategy run.
See the bullet about the onBar method:
https://www.dukascopy.com/wiki/#Strategy_API

now i have implemented it as follows. the code compiles and runs but all time settings for the mom inticator give the same result in testing. so i guess the onBar method does not receive the proper data for a 1 second period. what am i doing wrong? thanks

    @Configurable("Period") 
    public Period period = Period.createCustomPeriod(Unit.Second, 1);
    @Configurable("Feed data count for indicator calculation")
    public int dataCount = 5;
    @Configurable("feed type")
    public MyFeeds feedDataType = MyFeeds.CANDLESTICKS_1_SEC_ASK;
    @Configurable("open chart")
    public boolean openChart = false; 
    enum MyFeeds {
        //
        CANDLESTICKS_1_SEC_ASK(new TimePeriodAggregationFeedDescriptor(Instrument.XAUUSD, Period.ONE_SEC, OfferSide.ASK, Filter.NO_FILTER));
        //
        private final IFeedDescriptor feedDescriptor;
        MyFeeds(IFeedDescriptor feedDescriptor) { this.feedDescriptor = feedDescriptor; }
        public IFeedDescriptor getFeedDescriptor() { return feedDescriptor; }
    }   


@Override
    public void onStart(IContext context) throws JFException {
        this.context = context;                     
        engine = context.getEngine();               
        console = context.getConsole();             
        history = context.getHistory();             
        indicators = context.getIndicators();       

        IFeedDescriptor feedDescriptor = feedDataType.getFeedDescriptor();
        context.setSubscribedInstruments(new HashSet<Instrument>(Arrays.asList(new Instrument[] { feedDescriptor.getInstrument() })), true);
        if(openChart){            
            context.openChart(feedDescriptor);
        } 
        final int dataCount = 3;
        context.subscribeToFeed(feedDescriptor, new IFeedListener() {
        @Override
        public void onFeedData(IFeedDescriptor feedDescriptor, ITimedData feedData) {
            console.getOut().println(feedData + " of feed: " + feedDescriptor);
           
        }
    });
    }


public void onBar(Instrument instrument, Period period, IBar askBar, IBar bidBar) throws JFException {
        if (period != this.period) return;    
        if (instrument != this.instrument) return;  
        double mombuy      = indicators.mom(instrument, period, OfferSide.ASK, appliedprice, time, 1); 
        double momsell     = indicators.mom(instrument, period, OfferSide.BID, appliedprice, time, 1); 
}

You have to do the calculations inside the onFeedData method. And for calculation on feeds use the calculation method used in the feed example, more examples here:
https://www.dukascopy.com/wiki/#Indicator_Calculation/Universal_price_feed

ok i see... but does it mean it is not possible to tell the onBar method to run every 1 second?
that would be a lot more comfortable

You can pull out the onFeedData method, the following way:

package jforex.feed.indicators;

import com.dukascopy.api.*;
import com.dukascopy.api.IIndicators.AppliedPrice;
import com.dukascopy.api.feed.*;
import com.dukascopy.api.feed.util.TimePeriodAggregationFeedDescriptor;
import com.dukascopy.api.util.DateUtils;

public class MomOn1SecBars implements IStrategy, IFeedListener {

    private IIndicators indicators;
    private IConsole console;

    IFeedDescriptor feedDescriptorBuy = new TimePeriodAggregationFeedDescriptor(Instrument.EURUSD, Period.ONE_SEC, OfferSide.ASK, Filter.NO_FILTER);
    IFeedDescriptor feedDescriptorSell = new TimePeriodAggregationFeedDescriptor(Instrument.EURUSD, Period.ONE_SEC, OfferSide.BID, Filter.NO_FILTER);

    @Override
    public void onStart(IContext context) throws JFException {
        indicators = context.getIndicators();
        console = context.getConsole();
        context.subscribeToFeed(feedDescriptorBuy, this);

    }

    @Override
    public void onFeedData(IFeedDescriptor feedDescriptor, ITimedData feedData) {
        try {
            Object[] momBuyResult = indicators.calculateIndicator(feedDescriptorBuy, new OfferSide[] { feedDescriptor.getOfferSide() }, "MOM",
                    new AppliedPrice[] { AppliedPrice.CLOSE }, new Object[] { 10 }, 1);
            Object[] momSellResult = indicators.calculateIndicator(feedDescriptorSell, new OfferSide[] { feedDescriptor.getOfferSide() },
                    "MOM", new AppliedPrice[] { AppliedPrice.CLOSE }, new Object[] { 10 }, 1);
            double momBuy = (Double) momBuyResult[0];
            double momSell = (Double) momSellResult[0];
            console.getOut().format("sell %.7f buy %.7f at %s", momBuy, momSell, DateUtils.format(feedData.getTime())).println();
        } catch (JFException e) {
            console.getErr().println(e);
        }

    }

    public void onTick(Instrument instrument, ITick tick) throws JFException {}

    public void onBar(Instrument instrument, Period period, IBar askBar, IBar bidBar) throws JFException {}

    public void onMessage(IMessage message) throws JFException {}

    public void onAccount(IAccount account) throws JFException {}

    public void onStop() throws JFException {}

}

ok i got it ... thank you very much for your help