com.google.firebase.internal.DateUtils Maven / Gradle / Ivy
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/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.firebase.internal;
import static com.google.common.base.Preconditions.checkNotNull;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
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.
*
* Most of this class was borrowed from the
*
* Apache HTTP client in order to avoid a direct dependency on it. We currently
* have a transitive dependency on this library (via Google API client), but the API
* client team is working towards removing it, so we won't have it in the classpath for long.
*
*
The original implementation of this class uses
* thread locals to cache the {@code SimpleDateFormat} instances. Instead, this implementation
* uses static constants and explicit locking to ensure thread safety. This is probably slower,
* but also simpler and avoids memory leaks that may result from unreleased thread locals.
*/
final class DateUtils {
/**
* Date format pattern used to parse HTTP date headers in RFC 1123 format.
*/
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.
*/
static final String PATTERN_RFC1036 = "EEE, dd-MMM-yy HH:mm:ss zzz";
/**
* Date format pattern used to parse HTTP date headers in ANSI C
* {@code asctime()} format.
*/
static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";
private static final SimpleDateFormat[] DEFAULT_PATTERNS = new SimpleDateFormat[] {
new SimpleDateFormat(PATTERN_RFC1123, Locale.US),
new SimpleDateFormat(PATTERN_RFC1036, Locale.US),
new SimpleDateFormat(PATTERN_ASCTIME, Locale.US)
};
static final TimeZone GMT = TimeZone.getTimeZone("GMT");
static {
final Calendar calendar = Calendar.getInstance();
calendar.setTimeZone(GMT);
calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0);
calendar.set(Calendar.MILLISECOND, 0);
final Date defaultTwoDigitYearStart = calendar.getTime();
for (final SimpleDateFormat datePattern : DEFAULT_PATTERNS) {
datePattern.set2DigitYearStart(defaultTwoDigitYearStart);
}
}
/**
* Parses the date value using the given date formats.
*
* @param dateValue the date value to parse
* @return the parsed date or null if input could not be parsed
*/
public static Date parseDate(final String dateValue) {
String v = checkNotNull(dateValue);
// trim single quotes around date if present
// see issue #5279
if (v.length() > 1 && v.startsWith("'") && v.endsWith("'")) {
v = v.substring(1, v.length() - 1);
}
for (final SimpleDateFormat datePattern : DEFAULT_PATTERNS) {
final ParsePosition pos = new ParsePosition(0);
synchronized (datePattern) {
final Date result = datePattern.parse(v, pos);
if (pos.getIndex() != 0) {
return result;
}
}
}
return null;
}
/** This class should not be instantiated. */
private DateUtils() {
}
}