SafeSimpleDateFormat

SafeSimpleDateFormat.java

package jetbrick.util;

import java.text.DateFormatSymbols;
import java.text.FieldPosition;
import java.text.Format;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.TimeZone;

/**
 * This class implements a Thread-Safe (re-entrant) SimpleDateFormat
 * class.  It does this by using a ThreadLocal that holds a Map, instead
 * of the traditional approach to hold the SimpleDateFormat in a ThreadLocal.
 *
 * Each ThreadLocal holds a single HashMap containing SimpleDateFormats, keyed
 * by a String format (e.g. "yyyy/M/d", etc.), for each new SimpleDateFormat
 * instance that was created within the threads execution context.
 */
public final class SafeSimpleDateFormat extends Format {
    private static final long serialVersionUID = 1L;

    private static final ThreadLocal<Map<String, SimpleDateFormat>> _dateFormats = new ThreadLocal<Map<String, SimpleDateFormat>>() {
        @Override
        public Map<String, SimpleDateFormat> initialValue() {
            return new HashMap<String, SimpleDateFormat>();
        }
    };

    public static SimpleDateFormat getFormatter(String format) {
        Map<String, SimpleDateFormat> formatters = _dateFormats.get();
        SimpleDateFormat formatter = formatters.get(format);
        if (formatter == null) {
            formatter = new SimpleDateFormat(format);
            formatters.put(format, formatter);
        }
        return formatter;
    }

    private final String _format;

    public SafeSimpleDateFormat(String format) {
        _format = format;
    }

    @Override
    public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
        return getFormatter(_format).format(obj, toAppendTo, pos);
    }

    @Override
    public Object parseObject(String source, ParsePosition pos) {
        return getFormatter(_format).parse(source, pos);
    }

    public Date parse(String day) throws ParseException {
        return getFormatter(_format).parse(day);
    }

    public void setTimeZone(TimeZone tz) {
        getFormatter(_format).setTimeZone(tz);
    }

    public void setCalendar(Calendar cal) {
        getFormatter(_format).setCalendar(cal);
    }

    public void setNumberFormat(NumberFormat fmt) {
        getFormatter(_format).setNumberFormat(fmt);
    }

    public void setLenient(boolean lenient) {
        getFormatter(_format).setLenient(lenient);
    }

    public void setDateFormatSymbols(DateFormatSymbols symbols) {
        getFormatter(_format).setDateFormatSymbols(symbols);
    }

    public void set2DigitYearStart(Date date) {
        getFormatter(_format).set2DigitYearStart(date);
    }
}