Class deserialization - Differences between Jython and Java

Question

I was able to serialize a custom JFrame into a database, and I would like to deserialize it.
Unfortunately, during the alleged deserialization I have an error that I cannot resolve.

import sys

from java.io import *
from java.lang import Class
from java.sql import *
from methods import *


class MyFrame(JFrame):
    def __init__(self):
        self._title = 'Frame di prova'
        self.setTitle(self._title)
        c = self.getContentPane()

        self._insertN = JTextField(20)
        nameLabelPane, nameFieldPane = incidentPanels(
            JLabel("Nome"), [self._insertN])

        firstBlock = (nameLabelPane, nameFieldPane)

        firstPane = gridPane(firstBlock)

        if self._title.startswith('Modifica'):
            saveBtn = JButton('Modifica')
        else:
            saveBtn = JButton('Salva')

        globalPane = JPanel()
        gridBagger(globalPane, (firstPane, saveBtn))
        c.add(JScrollPane(globalPane))

        self.pack()


SQL_CREATE_TABLE = "create table if not exists serialized_java_objects (object_name varchar(1000), serialized_object blob)"
SQL_SERIALIZE_OBJECT = "INSERT INTO serialized_java_objects(object_name, serialized_object) VALUES (?, ?)"
SQL_DESERIALIZE_OBJECT = "SELECT serialized_object FROM serialized_java_objects limit 1"


def createTable(connection):
    connection.createStatement().executeUpdate(SQL_CREATE_TABLE)

def serializeJavaObjectToDB(connection, objectToSerialize):
    pstmt = connection.prepareStatement(SQL_SERIALIZE_OBJECT)

    pstmt.setString(1, 'Frame di prova')
    pstmt.setObject(2, objectToSerialize)
    pstmt.executeUpdate()
    pstmt.close()

def deSerializeJavaObjectFromDB(connection):
    pstmt = connection.prepareStatement(SQL_DESERIALIZE_OBJECT)
    rs = pstmt.executeQuery()
    rs.next()

    buf = rs.getBytes(1)
    objectIn = None
    if (buf != None):
        objectIn = ObjectInputStream(ByteArrayInputStream(buf))

    deSerializedObject = objectIn.readObject()

    rs.close()
    pstmt.close()

    return deSerializedObject


def getMySqlConnection():
    mysqlConn = None

    mysqlLog_server = "localhost"
    mysqlLog_username = "root"
    mysqlLog_password = ""
    mysqlLog_database = "tuttle"

    properties = Properties()
    properties.put("user", mysqlLog_username)
    properties.put("password", mysqlLog_password)

    url = "jdbc:mysql://" + mysqlLog_server + "/" + mysqlLog_database + \
        "?user=" + mysqlLog_username + "&password=" + mysqlLog_password

    mysqlConn = DriverManager.getConnection(url)
    return mysqlConn


def main(args):
    frame = MyFrame()
    Class.forName("com.mysql.jdbc.Driver")
    connection = getMySqlConnection()
    createTable(connection)

    serializeJavaObjectToDB(connection, frame)
    objFromDatabase = deSerializeJavaObjectFromDB(connection)

    objFromDatabase.setVisible(True)


if __name__ == '__main__':
    main(sys.argv)

The error is at the line objFromDatabase = deSerializeJavaObjectFromDB(connection), In particular on deSerializedObject = objectIn.readObject() and it's the following:

Traceback (most recent call last):
  File "provaSerializzazione.py", line 119, in <module>
    main(sys.argv)
  File "provaSerializzazione.py", line 113, in main
    objFromDatabase = deSerializeJavaObjectFromDB(connection)
  File "provaSerializzazione.py", line 74, in deSerializeJavaObjectFromDB
    deSerializedObject = objectIn.readObject()
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Unknown Source)
        at java.io.ObjectInputStream.resolveClass(Unknown Source)
        at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
        at java.io.ObjectInputStream.readClassDesc(Unknown Source)
        at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
        at java.io.ObjectInputStream.readObject0(Unknown Source)
        at java.io.ObjectInputStream.readObject(Unknown Source)
        at java.io.ObjectInputStream.readObject(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
java.lang.ClassNotFoundException: java.lang.ClassNotFoundException: org.python.proxies.__main__$MyFrame$3

Curious the fact that, if you replace the line frame = MyFrame() with frame = JFrame() the function serializes correctly, without errors.
It almost seems like the deserializing function doesn't accept a python class (which in turn extends a JFrame). What should I do to deserialize my MyFrame class in the jython language? Thanks in advance!

Answer 1

You need to use org.python.util.PythonObjectInputStream instead of java.io.ObjectInputStream.