从文件加载（不兼容的类）

Question

This is my first post to Stackoverflow, please be gentle :) I'm a beginner java developer working on an application for work where a class state needs to be saved to the network drive. I found it the easiest to save separately the attributes(there are only 2), as one attribute is accessed and modified(saved and loaded from) in a file a lot more than the other. On the other hand I would like to work on the program and improve it while it's in heavy use. The problem is that if I change something in the class implementation, then it's not compatible anymore with the state loaded from the file with the previous version of the class.

An example : Old Class: - name - address - phone number

New class: - name - address - phone number - age

Loading the old class from a file into the new class results in exception thrown being the loaded class incompatible with the new one. Is there any solution around it?

Thank you for your help in advance! :)

add: ohh, I'm using ObjectOutputStream for saving the file.

Answer 1

Store the state as XML. There is JAXB that in the new version can purely with annotations store/load class objects to/from XML.

This leaves more control (= needs more discipline to code what to persist). But is easy. Also can during development patch the XML a bit. (You need not use full JAXB with XSD.)