Homemade vs. Java Serialization

Question

I have a certain POJO which needs to be persisted on a database, current design specifies its field as a single string column, and adding additional fields to the table is not a

Answer 1

If you are using a delimiter you could use a character which you know would never occur in your text such as \0, or special symbols http://unicode.org/charts/symbols.html

However the time spent sending the data to the database and persisting it is likely to be much larger than the cost of serialization. So I would suggest starting with some thing simple and easy to read (like XStream) and look at where your application is spending most of its time and optimise that.

Answer 2

I have a certain POJO which needs to be persisted on a database, current design specifies its field as a single string column, and adding additional fields to the table is not an option.

Could you create a new table and put a foreign key into that column!?!? :) I suspect not, but let's cover all the bases!

Serialization: We've recently had this discussion so that if our application crashes we can resurrect it in the same state as previously. We essentially dispatch a persistance event onto a queue, and then this grabs the object, locks it, and then serializes it. This seems pretty quick. How much data are you serializing? Can you make any variables transient (i.e. cached variables)? Can you consider splitting up your serialization? Beware: what happens if your objects change (locking) or classes change (diferent serialization id)? You'll need to upgrade everything that's serialized to latest classes. Perhaps you only need to store this overnight so it doesn't matter?

XML: You could use something like xstream to achieve this. Building something custom is doable (a nice interview question!), but I'd probably not do it myself. Why bother? Remember if you have cyclic links or if you have referencs to objects more than once. Rebuilding the objects isn't quite so trivial.

Database storage: If you're using Oracle 10g to store blobs, upgrade to the latest version, since c/blob performance is massively increased. If we're talking large amounts of data, then perhaps zip the output stream?

Is this a realtime app, or will there be a second or two pauses where you can safely persist the actual object? If you've got time, then you could clone it and then persist the clone on another thread. What's the persistance for? Is it critical it's done inside a transaction?