Better way to store data in java?

I am currently working on a videogame, and i want to have the user be able to 开发者_运维知识库save their character to a new file. I know how to use the file io (for the most part), but i have been using the 'serialize' to serialize a whole object (that contains all the variables for the character) and save it to a file. The problem is that i am constantly updating the object and making changes to it, so when i try to load the old character with the new object, it errors and crashes. Same with levels as-well (an object holding a few 2d-array of variables).

There must be a better way to do this so it is compatible with future versions. If there is a way, would anybody please offer some source code and/or a link to a nice tutorial? All help is appreciated, thanks!!!

Use XML or an embedded database (fast and lightweight) such as Derby or H2. You could even use a plain old properties file.

In fact, see if the properties file will work for you. And only if that won't work, try XML or the embedded database approach.

if you are looking for java serializers here is the benchmark for you https://github.com/eishay/jvm-serializers/wiki/

Apache Avro seems to perform well.

Another way is to store the values in the persistent store like HSQLDB or H2 db and load it to memory at startup and persist when needed.You can also use SQLite (for driver check this)

You can implement Externalizable instead of Serializable, and in the readExternal() and writeExternal() methods you can put the logic to read/write the object. This way you have full control of serialization/deserialization and can make changes fairly easily. Alternatively you can use JSON serialization by using Gson. I would not recommend XML, but if you want to you can check out xstream for the same thing.

If you are extending your objects in backwards compatible ways, i.e. add fields, and not removing fields. Make sure that you have declared a serialVersionUID as per the serializable javadoc.

http://download.oracle.com/javase/1.5.0/docs/api/java/io/Serializable.html

One additional option to consider since you're already using serialization, you could implement Externalizable instead of Serializable. The code you use to serialize objects would remain the same. However in your class you would specify exactly how you want it serialized by overriding readExternal() and writeExternal(). E.g.:

public class MyClass implements Externalizable {
    private int foo;
    private String bar;

    public readExternal(ObjectInput in) {
        foo = in.readInt();
        bar = in.readUTF();
    }

    public writeExternal(ObjectOutput out) {
        out.writeInt(foo);
        out.writeUTF(bar);
    }
}

Just be sure to keep the order the same when reading and writing. Try to only add fields, however if you need to remove a field leave a gap to account for old versions.

Ultimately though if you're making a lot of changes it might best to switch to a properties or XML file as LES2 suggested. It'll be more portable and readable that way.

This game uses java.util.prefs.Preferences for cross-platform convenience. Because keys are stored individually, new additions rarely interfere with existing entries.