properties file in a jar

All,

I have a standard dev/test/prod enviroment. I also have my core classes in myapp.jar. I have your basic db connect string for each environment. So I am trying to do this right and have a properties file instead for hard coding a different string for each DB (among other things)

The problem is that the jar file is being used by many applications. Stand alone executable jar, web services, web applications, Eclipse IDE, etc... so my relative file path is different every time and - fails - the path is different every time

I cold hard code it from the root, but that's wrong, and it's different on every box.

There has to be a way of doing it so the path is relative to the jar file. Something like a class.forName("com.myapp.properties") so that nomater where the jar is being used, it can find the properties file.

Also, it should be easy to deploy with ant, like I copy the correct properties file into the /bin directory and simply jar it up.

Any ideas?

The trick to loading a .properties file (or any resource really) packaged inside a .jar file is using the ClassLoader#getResource???() family of methods.
Have a look at the documentation and see what comes up with a quick Google search.
You should be able to figure it out that way.

What am I doing wrong? I have tried every permutation of something like this:

I have tried all of these:
props.load(classLoader.getResourceAsStream("com.myapp.props.properties")); // with the file named "properties"
props.load(classLoader.getResourceAsStream("my.properties")); // with the file in the same directory as the class
props.load(classLoader.getResourceAsStream("my.properties")); // with the file in root directory of the jar

Any ideas?

This path is relative to the package of the current class. So if your class is named com.myapp.banana.Init, then the getResource() type methods will be looking for the path "/com/myapp/banana/com/myapp/props/my.properties" in the jar.

You must have missed the bit in the documentation which says to use a slash at the beginning if you want an absolute path. Like this:

Paul Clapham wrote:"com/myapp/props/my.properties"
This path is relative to the package of the current class.

Only if you use Class.getResource(AsStream). With ClassLoader.getResource(AsStream) it's relative to the class path. In this case I'd use the following:

Michael MacEachran wrote:What am I doing wrong? I have tried every permutation of something like this:

Properties props = new Properties(); ClassLoader classLoader = ClassLoader.getSystemClassLoader(); props.load(classLoader.getResourceAsStream("com/myapp/props/my.properties"));

That should work, but isn't your file called myapp.properties? It is according to your initial post.

Well, I cant get either of them to work. Now, because I have several classes that need a properties file I thought that I would move the my.properties to the root of the jar file and do this:

I open my jar file and at the root I have 2 directories com and META-INF and one file my.properties

that should work right? I am getting a NullPointerException

I have given up. My solution:

I set environment variables for what I want and used System.getenv()

Works on all platforms and class loaders!

Thank you for the help. I think the problem is that this jar is being used in many ways by many apps with different ways of loading the classes, so nothing seemed to work in all situations.

You shouldn't use a leading / when using ClassLoader to load the resources. That's only allowed when using Class to load them.