Class DateParser


  • public class DateParser
    extends Parser
    This is used to create a Parser for the HTTP date format. This will parse the 3 formats that are acceptable for the HTTP/1.1 date. The three formats that are acceptable for the HTTP-date are
     Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
     Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
     Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
     

    This can also parse the date in ms as retrived from the System's System.currentTimeMillis method. This has a parse method for a long which will do the same as the parse(String). Once the date has been parsed there are two methods that allow the date to be represented, the toLong method converts the date to a long and the toString method will convert the date into a String.

    This produces the same string as the SimpleDateFormat.format using the pattern "EEE, dd MMM yyyy hh:mm:ss 'GMT'". This will however do the job faster as it does not take arbitrary inputs.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private int day
      Represents the decimal value of the date such as 18.
      private int hour
      Represents the decimal value of the hour such as 24.
      private int mins
      Represents the decimal value of the minute.
      private int month
      Used as an index into the months array to get the month.
      private static java.lang.String[] MONTHS
      Contains the possible months in the year for HTTP-date.
      private int secs
      Represents the decimal value for the second.
      private int weekday
      Used as an index into the weekdays array to get the weekday.
      private static java.lang.String[] WEEKDAYS
      Contains the possible days of the week for RFC 850.
      private static java.lang.String[] WKDAYS
      Contains the possible days of the week for RFC 1123.
      private int year
      Represents the decimal value of the date such as 1977.
      private static java.util.TimeZone ZONE
      Ensure that the time zone for dates if set to GMT.
    • Constructor Summary

      Constructors 
      Constructor Description
      DateParser()
      The default constructor will create a parser that can parse Strings that contain dates in the form of RFC 1123, RFC 850 or asctime.
      DateParser​(long date)
      This constructor will conveniently parse the long argument in the constructor.
      DateParser​(java.lang.String date)
      This constructor will conveniently parse the String argument in the constructor.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      private void asctime()
      This will parse a date that is in the form of an asctime date.
      java.lang.String convert​(long date)
      Convenience method used to convert the specified long date in to a HTTP date format.
      long convert​(java.lang.String date)
      Convenience method used to convert the specified HTTP date in to a long representing the time.
      private void date​(java.lang.StringBuilder builder)
      This is used to append the date in RFC 1123 format to the given string builder.
      private void date1()
      This is the date1 format of a date that is used by the RFC 1123 date format.
      private void date2()
      This is the date2 format of a date that is used by the RFC 850 date format.
      private void date3()
      This is the date3 format of a date that is used by the asctime date format.
      private void day()
      This is used to parse a consecutive set of digit characters to create the day of the week.
      private void hours()
      This is used to initialize the hour.
      protected void init()
      This is used to reset the date and the buffer variables for this DateParser.
      private void mins()
      This is used to initialize the mins.
      private void month()
      This is used to read the month of HTTP-date.
      protected void parse()
      This is used to parse the contents of the buf.
      void parse​(long date)
      This is used to extract the date from a long.
      private void rfc1123()
      This will parse a date that is in the form of an RFC 1123 date.
      private void rfc850()
      This will parse a date that is in the form of an RFC 850 date.
      private void secs()
      This is used to initialize the secs.
      private void time()
      This is used to parse the time for a HTTP-date.
      private void time​(java.lang.StringBuilder builder)
      This is used to append the time in RFC 1123 format to the given string builder.
      long toLong()
      This returns the date in as a long, given the exact time this will use the java.util.Date to parse this date into a long.
      java.lang.String toString()
      This prints the date in the format of a RFC 1123 date.
      private void weekday()
      This is used to read the week day of HTTP-date.
      private void wkday()
      This is used to read the week day of HTTP-date.
      private void year2()
      This is used to get the year from a set of digit characters.
      private void year4()
      This is used to get the year from a set of digit characters.
      private void zone​(java.lang.StringBuilder builder)
      This is used to append the time zone to the provided appender.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    • Field Detail

      • ZONE

        private static final java.util.TimeZone ZONE
        Ensure that the time zone for dates if set to GMT.
      • WKDAYS

        private static final java.lang.String[] WKDAYS
        Contains the possible days of the week for RFC 1123.
      • WEEKDAYS

        private static final java.lang.String[] WEEKDAYS
        Contains the possible days of the week for RFC 850.
      • MONTHS

        private static final java.lang.String[] MONTHS
        Contains the possible months in the year for HTTP-date.
      • month

        private int month
        Used as an index into the months array to get the month.
      • year

        private int year
        Represents the decimal value of the date such as 1977.
      • day

        private int day
        Represents the decimal value of the date such as 18.
      • weekday

        private int weekday
        Used as an index into the weekdays array to get the weekday.
      • hour

        private int hour
        Represents the decimal value of the hour such as 24.
      • mins

        private int mins
        Represents the decimal value of the minute.
      • secs

        private int secs
        Represents the decimal value for the second.
    • Constructor Detail

      • DateParser

        public DateParser()
        The default constructor will create a parser that can parse Strings that contain dates in the form of RFC 1123, RFC 850 or asctime. If the dates that are to be parsed are not in the form of one of these date encodings the results of this parser will be random.
      • DateParser

        public DateParser​(long date)
        This constructor will conveniently parse the long argument in the constructor. This can also be done by first calling the no-arg constructor and then using the parse method.

        This will then set this object to one that uses the RFC 1123 format for a date.

        Parameters:
        date - the date to be parsed
      • DateParser

        public DateParser​(java.lang.String date)
        This constructor will conveniently parse the String argument in the constructor. This can also be done by first calling the no-arg constructor and then using the parse method.

        This will then set this object to one that uses the RFC 1123 format for a date.

        Parameters:
        date - the date to be parsed
    • Method Detail

      • parse

        public void parse​(long date)
        This is used to extract the date from a long. If this method is given the value of the date as a long it will construct the RFC 1123 date as required by RFC 2616 sec 3.3.

        This saves time on parsing a String that is encoded in the HTTP-date format. The date given must be positive, if the date given is not a positive 'long' then the results of this method is random/unknown.

        Parameters:
        date - the date to be parsed
      • convert

        public long convert​(java.lang.String date)
        Convenience method used to convert the specified HTTP date in to a long representing the time. This is used when a single method is required to convert a HTTP date format to a usable long value for use in creating Date objects.
        Parameters:
        date - the date specified in on of the HTTP date formats
        Returns:
        the date value as a long value in milliseconds
      • convert

        public java.lang.String convert​(long date)
        Convenience method used to convert the specified long date in to a HTTP date format. This is used when a single method is required to convert a long data value in milliseconds to a HTTP date value.
        Parameters:
        date - the date specified as a long of milliseconds
        Returns:
        the date represented in the HTTP date format RFC 1123
      • init

        protected void init()
        This is used to reset the date and the buffer variables for this DateParser. Every in is set to the value of 0.
        Specified by:
        init in class Parser
      • parse

        protected void parse()
        This is used to parse the contents of the buf. This checks the fourth char of the buffer to see what it contains. Invariably a date format belonging to RFC 1123 will have a ',' character in position 4, a date format belonging to asctime will have a ' ' character in position 4 and if neither of these characters are found at position 4 then it is assumed that the date is in the RFC 850 fromat, however it may not be.
        Specified by:
        parse in class Parser
      • rfc1123

        private void rfc1123()
        This will parse a date that is in the form of an RFC 1123 date. This date format is the date format that is to be used with all applications that are HTTP/1.1 compliant. The RFC 1123 date format is
         rfc1123 = 'wkday "," SP date1 SP time SP GMT'. 
         date1 = '2DIGIT SP month SP 4DIGIT' and finally
         time = '2DIGIT ":" 2DIGIT ":" 2DIGIT'. 
         
      • rfc850

        private void rfc850()
        This will parse a date that is in the form of an RFC 850 date. This date format is the date format that is to be used with some applications that are HTTP/1.0 compliant. The RFC 1123 date format is
         rfc850 = 'weekday "," SP date2 SP time SP GMT'. 
         date2 = '2DIGIT "-" month "-" 2DIGIT' and finally
         time = '2DIGIT ":" 2DIGIT ":" 2DIGIT'. 
         
      • asctime

        private void asctime()
        This will parse a date that is in the form of an asctime date. This date format is the date format that is to be used with some applications that are HTTP/1.0 compliant. The RFC 1123 date format is
         asctime = 'weekday SP date3 SP time SP 4DIGIT'. 
         date3 = 'month SP (2DIGIT | (SP 1DIGIT))' and 
         time = '2DIGIT ":" 2DIGIT ":" 2DIGIT'. 
         
      • date1

        private void date1()
        This is the date1 format of a date that is used by the RFC 1123 date format. This date is
         date1 = '2DIGIT SP month SP 4DIGIT'.
         example '02 Jun 1982'.
         
      • date2

        private void date2()
        This is the date2 format of a date that is used by the RFC 850 date format. This date is
         date2 = '2DIGIT "-" month "-" 2DIGIT'
         example '02-Jun-82'.
         
      • date3

        private void date3()
        This is the date3 format of a date that is used by the asctime date format. This date is
         date3 = 'month SP (2DIGIT | (SP 1DIGIT))' 
         example 'Jun  2'.
         
      • day

        private void day()
        This is used to parse a consecutive set of digit characters to create the day of the week. This will tolerate a space on front of the digits thiswill allow all date formats including asctime to use this to get the day. This may parse more than 2 digits, however if there are more than 2 digits the date format is incorrect anyway.
      • year2

        private void year2()
        This is used to get the year from a set of digit characters. This is used to parse years that are of the form of 2 digits (e.g 82) however this will assume that any dates that are in 2 digit format are dates for the 2000 th milleneum so 01 will be 2001.

        This may parse more than 2 digits but if there are more than 2 digits in a row then the date format is incorrect anyway.

      • year4

        private void year4()
        This is used to get the year from a set of digit characters. This is used to parse years that are of the form of 4 digits (e.g 1982).

        This may parse more than 4 digits but if there are more than 2 digits in a row then the date format is incorrect anyway.

      • time

        private void time()
        This is used to parse the time for a HTTP-date. The time for a HTTP-date is in the form 00:00:00 that is
         time = '2DIGIT ":" 2DIGIT ":" 2DIGIT' so this will
         read only a time of that form, although this will
         parse time = '2DIGIT CHAR 2DIGIT CHAR 2DIGIT'.
         
      • hours

        private void hours()
        This is used to initialize the hour. This will read a consecutive sequence of digit characters and convert them into a decimal number to represent the hour that this date represents.

        This may parse more than 2 digits but if there are more than 2 digits the date is already incorrect.

      • mins

        private void mins()
        This is used to initialize the mins. This will read a consecutive sequence of digit characters and convert them into a decimal number to represent the mins that this date represents.

        This may parse more than 2 digits but if there are more than 2 digits the date is already incorrect.

      • secs

        private void secs()
        This is used to initialize the secs. This will read a consecutive sequence of digit characters and convert them into a decimal number to represent the secs that this date represents.

        This may parse more than 2 digits but if there are more than 2 digits the date is already incorrect

      • wkday

        private void wkday()
        This is used to read the week day of HTTP-date. The shorthand day (e.g Mon for Monday) is used by the RFC 1123 and asctime date formats. This will simply try to read each day from the buffer, when the day is read successfully then the index of that day is saved.
      • weekday

        private void weekday()
        This is used to read the week day of HTTP-date. This format is used by the RFC 850 date format. This will simply try to read each day from the buffer, when the day is read successfully then the index of that day is saved.
      • month

        private void month()
        This is used to read the month of HTTP-date. This will simply try to read each month from the buffer, when the month is read successfully then the index of that month is saved.
      • date

        private void date​(java.lang.StringBuilder builder)
        This is used to append the date in RFC 1123 format to the given string builder. This will append the date and a trailing space character to the buffer. Dates like the following are appended.
         Tue, 02 Jun 1982 
         
        . For performance reasons a string builder is used. This avoids an unneeded synchronization caused by the string buffers.
        Parameters:
        builder - this is the builder to append the date to
      • time

        private void time​(java.lang.StringBuilder builder)
        This is used to append the time in RFC 1123 format to the given string builder. This will append the time and a trailing space character to the buffer. Times like the following are appended.
         23:59:59
         
        . For performance reasons a string builder is used. This avoids an unneeded synchronization caused by the string buffers.
        Parameters:
        builder - this is the builder to write the time to
      • zone

        private void zone​(java.lang.StringBuilder builder)
        This is used to append the time zone to the provided appender. For HTTP the dates should always be in GMT format. So this will simply append the "GMT" string to the end of the builder.
        Parameters:
        builder - this builder to append the time zone to
      • toLong

        public long toLong()
        This returns the date in as a long, given the exact time this will use the java.util.Date to parse this date into a long. The GregorianCalendar uses the method getTime which produces the Date object from this the getTime returns the long
        Returns:
        the date parsed as a long
      • toString

        public java.lang.String toString()
        This prints the date in the format of a RFC 1123 date. Example
         Tue, 02 Jun 1982 23:59:59 GMT
         
        . This uses a StringBuffer to accumulate the various Strings/ints to form the resulting date value. The resulting date value is the one required by RFC 2616.

        The HTTP date must be in the form of RFC 1123. The hours, minutes and seconds are appended with the 0 character if they are less than 9 i.e. if they do not have two digits.

        Overrides:
        toString in class java.lang.Object
        Returns:
        the date in RFC 1123 format