How to read time fields?

[ophiry]

i'm having troubles reading time objects - the resulting object contains an 8 byte binary buffer, but I'm not sure how to interpret it

example: (serialized date is around 1/1/2016)

serialized_time_object = '\xac\xed\x00\x05sr\x00\rjava.time.Ser\x95]\x84\xba\x1b"H\xb2\x0c\x00\x00xpw\x08\x05\x00\x00\x07\xe0\x01\x01\xffx'

time_object = javaobj.loads(serialized_time_object)

time_object.__dict__

{'annotations': ['\x05\x00\x00\x07\xe0\x01\x01\xff'], 'classdesc':
[java.time.Ser:0x-6AA27B45E4DDB74E]}

struct.unpack('L',time_object.annotations[0])(0)

18374970016350076933L

[tcalmant]

Hi,
Java uses a custom serialization for this type of object, as can be seen in the source.

It is therefor necessary to read the content of annotations as the bytes written by the JVM, therefore you have to read:

1. A byte indicating the type
2. The time, according to the type

In the case of your snippet, we get "type" as 5: LocalDateTime, which is in fact serialized as a LocalDate followed by a LocalTime.

This following snippet handles this kind of times, following the source code of java.time.Ser, LocalDate and LocalTime.
Note that '>' in format string is mandatory as Java serialization uses Big Endian.

import javaobj
import struct

serialized_time_object = b'\xac\xed\x00\x05sr\x00\rjava.time.Ser\x95]\x84\xba\x1b"H\xb2\x0c\x00\x00xpw\x08\x05\x00\x00\x07\xe0\x01\x01\xffx'
time_object = javaobj.loads(serialized_time_object)

def read(data, fmt_str):
    size = struct.calcsize(fmt_str)
    return struct.unpack(fmt_str, data[:size]), data[size:]

# This is for Python 3, to ensure we have bytes
data = time_object.annotations[0].encode('latin1')

# This will give us the kind of date (type 5: [LocalDateTime](http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8-b132/java/time/Ser.java#100))
(time_type,), data = read(data, '>b')

Now we just have to follow the deserialization process from the Java source code:
# Start with the date
(year, month, day_of_month), data = read(data, '>ibb')

# Then the time
(hour,), data = read(data, '>b')
minute = 0
second = 0
nano = 0

if hour < 0:
    hour = ~hour
else:
    minute = read(data, '>b')
    if minute < 0:
        minute = ~minute
    else:
        second = read(data, '>b')
        if second < 0:
            second = ~second
        else:
            nano = read(data, '>i')

print("Date:", year, month, day_of_month, hour, minute, second, nano)