Storing Data

1. Storing Data

2. A Note About Creating Games

3. Why do you want to store data? • Data files • Configuration files

4. Configuration files Pros: • Pulls crap like strings and constants out of your code • Lets the same code run with different configurations at runtime • Others can edit the configuration files themselves…sometimes the configuration files are a programming language unto themselves • Centralizes config stuff Cons: • You now must consider file management

5. Example Config File Application: Internationalized Applications • Instead of JButtonmyButton = new JButton(“Press Here to Continue”); JButtonmyButton = new JButton(StringConfig.getStringFor(“PRESS_HERE”));

6. How do I store data? • The right answer is almost always not write a file format yourself • Know and use the right tool for the job: • Write the file format yourself (flat file) • Serializing • XML • JSON • Databases

7. Flat File Pros: • Pretty Easy • Requires no fancy libraries whatsoever • You have total control, so you can deal with space/performance constraints directly (though this is not usually particularly easy) Cons: • Parsing is notoriously error prone • If you don’t deal with speed, it’s slow • Concurrency and half written files are an issue

8. Serializing • Pros • Super duper easy to use, even with complex data • Cons • Can have complex issues with versioning (especially in a strongly typed language like Java) • Sometimes tied to language or library version • Not hand-editable, usually • Be sure you’re only serializing what you intend to • If something is half-written or has concurrency problems, expect to toss the whole file in the trash

9. XML • Pros • Will parse for you, including some nice searching • XML library ensures you always have a well formatted file • Super portable format that almost anybody can read • Cons • Search/update is still slow • Concurrency and half written files are an issue • Super verbose, and those XML libraries are often a major pain to use

10. JSON • Pros • Will parse for you • JSON library ensures you always have a well formatted file • Portable format that almost anybody can read (but you usually will need to download a small library for most languages) • Easy to use! Hand editable • Cons • Fancy-smancycorperate folks will complain that you didn’t use XML • Have to read everything into memory so it’s not suitable for giant chunks of data • Concurrency and half written files are an issue

11. Databases • Pros • Lots of built in protection to prevent corruption and allow concurrency • Fast even with a large amount of data • Has a query language (usually SQL) that lets you do arbitrary kinds of searches on data • Cons • Tricky to set up • Abandon all hopes of hand editing, but you can update with queries • For high performance, you have to understand how things work under the hood

12. JSON Sample • Please snarf the code for today’s class • You’ll need to download the JSON library Gson (URL is in the snarfed code) • Modify the code to output a Map to a file and read it back • When you’re finished, submit the code via ambient