datetool.java

一个用于java web页面开发的开源包

        }
        // do they want a time instance?
        else if (format.endsWith("_time"))
        {
            String fmt = format.substring(0, format.length() - 5);
            int style = getStyleAsInt(fmt);
            df = getDateFormat(-1, style, locale, timezone);
        }
        // ok, they either want a custom or date-time instance
        else
        {
            int style = getStyleAsInt(format);
            if (style < 0)
            {
                // we have a custom format
                df = new SimpleDateFormat(format, locale);
                df.setTimeZone(timezone);
            }
            else
            {
                // they want a date-time instance
                df = getDateFormat(style, style, locale, timezone);
            }
        }
        return df;
    }

    /**
     * Returns a {@link DateFormat} instance for the specified
     * date style, time style, {@link Locale}, and {@link TimeZone}.
     *
     * @param dateStyle the date style
     * @param timeStyle the time style
     * @param locale the {@link Locale} to be used
     * @param timezone the {@link TimeZone} to be used
     * @return an instance of {@link DateFormat}
     * @see #getDateFormat(int timeStyle, int dateStyle, Locale locale, TimeZone timezone)
     * @since VelocityTools 1.1
     */
    public DateFormat getDateFormat(String dateStyle, String timeStyle,
                                    Locale locale, TimeZone timezone)
    {
        int ds = getStyleAsInt(dateStyle);
        int ts = getStyleAsInt(timeStyle);
        return getDateFormat(ds, ts, locale, timezone);
    }

    /**
     * Returns a {@link DateFormat} instance for the specified
     * time style, date style, {@link Locale}, and {@link TimeZone}.
     *
     * @param dateStyle the date style (date will be ignored if this is
     *        less than zero and the date style is not)
     * @param timeStyle the time style (time will be ignored if this is
     *        less than zero and the date style is not)
     * @param locale the {@link Locale} to be used
     * @param timezone the {@link TimeZone} to be used
     * @return an instance of {@link DateFormat} or <code>null</code>
     *         if an instance cannot be constructed with the given
     *         parameters
     * @since VelocityTools 1.1
     */
    protected DateFormat getDateFormat(int dateStyle, int timeStyle,
                                       Locale locale, TimeZone timezone)
    {
        try
        {
            DateFormat df;
            if (dateStyle < 0 && timeStyle < 0)
            {
                // no style was specified, use default instance
                df = DateFormat.getInstance();
            }
            else if (timeStyle < 0)
            {
                // only a date style was specified
                df = DateFormat.getDateInstance(dateStyle, locale);
            }
            else if (dateStyle < 0)
            {
                // only a time style was specified
                df = DateFormat.getTimeInstance(timeStyle, locale);
            }
            else
            {
                df = DateFormat.getDateTimeInstance(dateStyle, timeStyle,
                                                    locale);
            }
            df.setTimeZone(timezone);
            return df;
        }
        catch (Exception suppressed)
        {
            // let it go...
            return null;
        }
    }

    /**
     * Checks a string to see if it matches one of the standard DateFormat
     * style patterns: FULL, LONG, MEDIUM, SHORT, or DEFAULT.  If it does,
     * it will return the integer constant for that pattern.  If not, it
     * will return -1.
     *
     * @see DateFormat
     * @param style the string to be checked
     * @return the int identifying the style pattern
     * @since VelocityTools 1.1
     */
    protected int getStyleAsInt(String style)
    {
        // avoid needlessly running through all the string comparisons
        if (style == null || style.length() < 4 || style.length() > 7) {
            return -1;
        }
        if (style.equalsIgnoreCase("full"))
        {
            return DateFormat.FULL;
        }
        if (style.equalsIgnoreCase("long"))
        {
            return DateFormat.LONG;
        }
        if (style.equalsIgnoreCase("medium"))
        {
            return DateFormat.MEDIUM;
        }
        if (style.equalsIgnoreCase("short"))
        {
            return DateFormat.SHORT;
        }
        if (style.equalsIgnoreCase("default"))
        {
            return DateFormat.DEFAULT;
        }
        // ok, it's not any of the standard patterns
        return -1;
    }


    // ------------------------- date conversion methods ---------------

    /**
     * Converts an object to an instance of {@link Date} using the
     * format returned by {@link #getFormat()},the {@link Locale} returned
     * by {@link #getLocale()}, and the {@link TimeZone} returned by
     * {@link #getTimeZone()} if the object is not already an instance
     * of Date, Calendar, or Long.
     *
     * @param obj the date to convert
     * @return the object as a {@link Date} or <code>null</code> if no
     *         conversion is possible
     */
    public Date toDate(Object obj)
    {
        return toDate(getFormat(), obj, getLocale(), getTimeZone());
    }

    /**
     * Converts an object to an instance of {@link Date} using the
     * specified format,the {@link Locale} returned by
     * {@link #getLocale()}, and the {@link TimeZone} returned by
     * {@link #getTimeZone()} if the object is not already an instance
     * of Date, Calendar, or Long.
     *
     * @param format - the format the date is in
     * @param obj - the date to convert
     * @return the object as a {@link Date} or <code>null</code> if no
     *         conversion is possible
     * @see #toDate(String format, Object obj, Locale locale)
     */
    public Date toDate(String format, Object obj)
    {
        return toDate(format, obj, getLocale(), getTimeZone());
    }

    /**
     * Converts an object to an instance of {@link Date} using the
     * specified format and {@link Locale} if the object is not already
     * an instance of Date, Calendar, or Long.
     *
     * @param format - the format the date is in
     * @param obj - the date to convert
     * @param locale - the {@link Locale}
     * @return the object as a {@link Date} or <code>null</code> if no
     *         conversion is possible
     * @see SimpleDateFormat#parse
     */
    public Date toDate(String format, Object obj, Locale locale)
    {
        return toDate(format, obj, locale, getTimeZone());
    }

    /**
     * Converts an object to an instance of {@link Date} using the
     * specified format, {@link Locale}, and {@link TimeZone} if the
     * object is not already an instance of Date, Calendar, or Long.
     *
     * @param format - the format the date is in
     * @param obj - the date to convert
     * @param locale - the {@link Locale}
     * @param timezone - the {@link TimeZone}
     * @return the object as a {@link Date} or <code>null</code> if no
     *         conversion is possible
     * @see #getDateFormat
     * @see SimpleDateFormat#parse
     */
    public Date toDate(String format, Object obj,
                       Locale locale, TimeZone timezone)
    {
        if (obj == null)
        {
            return null;
        }
        if (obj instanceof Date)
        {
            return (Date)obj;
        }
        if (obj instanceof Calendar)
        {
            return ((Calendar)obj).getTime();
        }
        if (obj instanceof Number)
        {
            Date d = new Date();
            d.setTime(((Number)obj).longValue());
            return d;
        }
        try
        {
            //try parsing w/a customized SimpleDateFormat
            DateFormat parser = getDateFormat(format, locale, timezone);
            return parser.parse(String.valueOf(obj));
        }
        catch (Exception e)
        {
            return null;
        }
    }

    /**
     * Converts an object to an instance of {@link Calendar} using the
     * locale returned by {@link #getLocale()} if necessary.
     *
     * @param obj the date to convert
     * @return the converted date
     * @see #toCalendar(Object obj, Locale locale)
     */
    public Calendar toCalendar(Object obj)
    {
        return toCalendar(obj, getLocale());
    }

    /**
     * Converts an object to an instance of {@link Calendar} using the
     * locale returned by {@link #getLocale()} if necessary.
     *
     * @param obj the date to convert
     * @param locale the locale used
     * @return the converted date
     * @see #toDate(String format, Object obj, Locale locale)
     * @see Calendar
     */
    public Calendar toCalendar(Object obj, Locale locale)
    {
        if (obj == null)
        {
            return null;
        }
        if (obj instanceof Calendar)
        {
            return (Calendar)obj;
        }
        //try to get a date out of it
        Date date = toDate(obj);
        if (date == null)
        {
            return null;
        }

        //convert the date to a calendar
        Calendar cal = Calendar.getInstance(locale);
        cal.setTime(date);
        // HACK: Force all fields to update. see link for explanation of this.
        //http://java.sun.com/j2se/1.4/docs/api/java/util/Calendar.html
        cal.getTime();
        return cal;
    }


    // ------------------------- default toString() implementation ------------

    /**
     * @return the result of {@link #getDate()} formatted according to the result
     *         of {@link #getFormat()}.
     * @see #format(String format, Object obj)
     */
    public String toString()
    {
        return format(getFormat(), getDate());
    }


}