Mega Code Archive
Parsing and formatting HTTP dates as used in cookies and other headers
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import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;
/**
* A utility class for parsing and formatting HTTP dates as used in cookies and
* other headers. This class handles dates as defined by RFC 2616 section
* 3.3.1 as well as some other common non-standard formats.
*
* @author Christopher Brown
* @author Michael Becke
*/
public final class DateUtil {
/**
* Date format pattern used to parse HTTP date headers in RFC 1123 format.
*/
public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
/**
* Date format pattern used to parse HTTP date headers in RFC 1036 format.
*/
public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";
/**
* Date format pattern used to parse HTTP date headers in ANSI C
* <code>asctime()</code> format.
*/
public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
private static final Collection<String> DEFAULT_PATTERNS = Arrays.asList(
new String[] {PATTERN_ASCTIME, PATTERN_RFC1036, PATTERN_RFC1123});
private static final Date DEFAULT_TWO_DIGIT_YEAR_START;
static {
Calendar calendar = Calendar.getInstance();
calendar.set(2000, Calendar.JANUARY, 1, 0, 0);
DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime();
}
private static final TimeZone GMT = TimeZone.getTimeZone("GMT");
/**
* This class should not be instantiated.
*/
private DateUtil() {
}
/**
* Parses a date value. The formats used for parsing the date value are retrieved from
* the default http params.
*
* @param dateValue the date value to parse
* @return the parsed date
* @throws DateParseException if the value could not be parsed using any of the
* supported date formats
*/
public static Date parseDate(String dateValue) {
return parseDate(dateValue, null, null);
}
/**
* Parses the date value using the given date formats.
*
* @param dateValue the date value to parse
* @param dateFormats the date formats to use
* @return the parsed date
* @throws DateParseException if none of the dataFormats could parse the dateValue
*/
public static Date parseDate(String dateValue, Collection<String> dateFormats)
{
return parseDate(dateValue, dateFormats, null);
}
/**
* Parses the date value using the given date formats.
*
* @param dateValue the date value to parse
* @param dateFormats the date formats to use
* @param startDate During parsing, two digit years will be placed in the range
* <code>startDate</code> to <code>startDate + 100 years</code>. This value may
* be <code>null</code>. When <code>null</code> is given as a parameter, year
* <code>2000</code> will be used.
* @return the parsed date
* @throws DateParseException if none of the dataFormats could parse the dateValue
*/
public static Date parseDate(
String dateValue,
Collection<String> dateFormats,
Date startDate
) {
if (dateValue == null) {
throw new IllegalArgumentException("dateValue is null");
}
if (dateFormats == null) {
dateFormats = DEFAULT_PATTERNS;
}
if (startDate == null) {
startDate = DEFAULT_TWO_DIGIT_YEAR_START;
}
// trim single quotes around date if present
// see issue #5279
if (dateValue.length() > 1
&& dateValue.startsWith("'")
&& dateValue.endsWith("'")
) {
dateValue = dateValue.substring(1, dateValue.length() - 1);
}
SimpleDateFormat dateParser = null;
for (String format : dateFormats) {
if (dateParser == null) {
dateParser = new SimpleDateFormat(format, Locale.US);
dateParser.setTimeZone(TimeZone.getTimeZone("GMT"));
dateParser.set2DigitYearStart(startDate);
} else {
dateParser.applyPattern(format);
}
try {
return dateParser.parse(dateValue);
} catch (ParseException pe) {
// ignore this exception, we will try the next format
}
}
// we were unable to parse the date
throw new RuntimeException("Unable to parse the date " + dateValue);
}
/**
* Formats the given date according to the RFC 1123 pattern.
*
* @param date The date to format.
* @return An RFC 1123 formatted date string.
* @see #PATTERN_RFC1123
*/
public static String formatDate(Date date) {
return formatDate(date, PATTERN_RFC1123);
}
/**
* Formats the given date according to the specified pattern. The pattern
* must conform to that used by the {@link SimpleDateFormat simple date
* format} class.
*
* @param date The date to format.
* @param pattern The pattern to use for formatting the date.
* @return A formatted date string.
* @throws IllegalArgumentException If the given date pattern is invalid.
* @see SimpleDateFormat
*/
public static String formatDate(Date date, String pattern) {
if (date == null) {
throw new IllegalArgumentException("date is null");
}
if (pattern == null) {
throw new IllegalArgumentException("pattern is null");
}
SimpleDateFormat formatter = new SimpleDateFormat(pattern, Locale.US);
formatter.setTimeZone(GMT);
return formatter.format(date);
}
}
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