Application configuration files for Glassfish/Java EE 5 web services - configuration

Question

I am trying to write some simple Java web services so we can call Java code from .NET. So far, I got a proof-of-concept working under Glassfish. Pretty straightforward when the IDE does all the work.
Now I'm really bogging down on stuff in Java that should be really simple. For example, I want to externalize my configuration so I can change stuff like connection strings/usernames/application variables/etc without recompiling.
In .NET, you would just stick some strings in the web.config file in the root of the web site and use: ConfigurationManager.AppSettings["whateverIwant"];
I can get java.util.Properties to do what I want (from a standalone client), but I can't figure out where to put the .properties file and how to get the path to it from within the web service.
I need my approach to work within WebSphere Application Server as well. Thanks!

Answer 1

As others have mentioned, it greatly depends on the container, but almost always dynamic configurations are stored in a database instead of XML or .properties files.
As I see that this is just like a proof of concept, here's a quick and dirty solution: (don't do this for production code) use System Properties.
Disadvantage: with every change you need to reboot the container, but you don't need to recompile the app.
To use system properties in Glassfish you can go to the section "Configuration -> System Properties" and add properties there. Then from inside your application just call
String myValue = System.getProperty("myProperty");
To get the value. All java applications support these properties, but I don't know how to configure them in Websphere.

Answer 2

Alas, Java EE has a giant hole in the head when it comes to application configuration.
Your best bet is to either:
use JNDI to store config in the application server environment. This is hard to do portably, painful, and an absolute nightmare for the user to do any configuration. Configuration UI depends on which app server and version is in use and may be a command-line-only utility specific to that app server.
Use the Preferences API to store your configuration, and produce your own UI to edit it. This is OK ... except that you can't control when your settings are flushed and re-inited. Some app servers will do this when your app is re-deployed, which you probably don't want.
All in all, the situation absolutely stinks. There's no clean, sensible way for an app server to provide an app with a simple properties map and UI to edit it using the app server's admin tools.
I tried to work around this using web context parameters, but found that they too were buggy. Glassfish was ignoring more than the first web context parameter that was being set, and they were hard to access without having a servlet context so you couldn't really get to them easily across the whole app.
If anyone has a better answer I'd love to hear it, because the situation as it stands seems downright amazing for a spec that's been through several major iterations.
see also: Storing and editing configuration for Java EE applications

Answer 3

Application configuration is unfortunately container dependent. In general you access your configuration through JNDI. The approach I've recently used was the following:
Make a database available to your app (through JNDI, use the Glassfish database "wizard"). This is part is container dependent.
Create an entity bean that deserializes your settings from the database. The simple solution here is to have something like this:
#Entity
public class Setting {
#Id
private String name;
private String value;
...
}
Then it's a question of doing em.find(Setting.class, "whateveriwant").getValue(). Alternatively, you could create a single entity bean with all the settings as attributes.
Either way, this approach reduces the container dependency to a minimum.

Answer 4

The best solution I've found so far is "EAC4J (External Application Configuration For Java)". I've used successfully in many projects.

Answer 5

Put the following code in the contextInitialized method of a ServletContextListener:
ServletContext sc = sce.getServletContext();
Properties systemProps = System.getProperties();
String path = sc.getRealPath("WEB-INF/application.properties");
systemProps.load(new FileInputStream(path));
This reads from application.properties from the the WEB-INF folder of your web app when it starts. This will require a restart every time the configs change, but in my opinion, that is as it should be.