CODEWITHSUNDEEP
javajarfile-access
sten
sten

Reputation: 7476

Standard/Uniform way to locate files inside and outside JAR file?

What is the uniform or standard way to locate and then access files inside and outside JAR files.

I have InJarClass() defined in JAR file which contains configuration text files. Then I extend this class in my host project which have more configurations.

Let say I have inside the JAR :

config/default.conf

Then in the host project I do :

class MyClass extends InJarClass { .... }

and also :

config/test.conf

then I run it something like this :

XENV=test java myclass

The whole configuration process happens inside InJarClass(), based on environment XENV. As you see InJarClass() have to access both :

<jar>/config/default.conf
<host_app_dir>/config/test.conf

So to repeat my question is there uniform way to access both, if the directory structure mirror each other.

Upvotes: 0

Views: 135

Answers (1)

VGR
VGR

Reputation: 44328

If you place both the current directory and the .jar file in your classpath:

XENV=test java -classpath .:myjarfile.jar MyClass

you can do this:

String configFile =
    "/config/" +
    System.getenv().getOrDefault("XENV", "default") +
    ".conf";

InputStream config = MyClass.class.getResourceAsStream(configFile);

if (config == null) {
    throw new FileNotFoundException(
        "Cannot locate " + configFile + " in classpath");
}

This works because an application resource is a resource which Java searches for within each location in the classpath. So getResourceAsStream will first search for the requested path relative to the first classpath location, .. If it does not find a file with that name, it will look at the second classpath location, myjarfile.jar, and seeing that it is a .jar file, will search for the requested file inside that .jar.

Upvotes: 1

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