For a while now I have been toying with the idea of using source code as a file storage format.
My question: How to support format version changes? (loading of older files with structural differences)
An example would be a settings file.
JSON:
{ "version": 1, "email": "[email protected]" } Then there is typically a manual or automatic parsing/deserialization/binding step that maps the textual information to a typed model in memory, e.g. an object of type Settings:
public class Settings { public String email; } Using source code as storage format, the settings file would look like this:
//version=1 public class MySettingsFile1 { public static final int VERSION = 1; public static Settings load() { Settings s = new Settings(); s.email = "[email protected]"; return s; } } The settings file could then be loaded by leveraging the class loading mechanism:
String className = "MySettingsFile1"; String source = ... (read settings file to string) Class<?> clazz = new CustomClassLoader().compileAndLoad(className, source); Settings settings = (Settings) clazz.getMethod("load").invoke(null); System.out.println(settings.email); I already know out how to load a class from a String.
Pros
- no parsing / binding code required
- text format (human readable)
- concise (verbosity comparable to JSON)
- supports comments
Cons
- how to support different versions and upgrade from older versions?
- security (sandbox the loading code?)
Edit: The real use case I have in mind are files that are only modified by a custom GUI editor, and then compiled and packaged with the application (no security concerns here). These files are already under version control (XML currently).