How to read a directory from the runtime classpath?

Question

My Java application needs to be able to find a myconfig/ directory which will be bundled inside the same JAR:

myjar.jar/
    com/
        me/
           


        

Answer 1

You could call ClassLoader.getResource() to find a particular file in the directory (or the directory itself, if getResource() will return directories). getResource() returns a URL pointing to the result. You could then convert this URL into whatever form the other library requires.

Answer 2

The trick seems to be that the class loader can find directories in the classpath, while the class can not.

So this works

this.getClass().getClassLoader().getResource("com/example/foo/myconfig");

while this does not

this.getClass().getResource("myconfig");

Answer 3

You can use the PathMatchingResourcePatternResolver provided by Spring.

public class SpringResourceLoader {

    public static void main(String[] args) throws IOException {
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();

        // Ant-style path matching
        Resource[] resources = resolver.getResources("/myconfig/**");

        for (Resource resource : resources) {
            InputStream is = resource.getInputStream();
            ...
        }
    }
}

I didn't do anything fancy with the returned Resource but you get the picture.

Add this to your maven dependency (if using maven):

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>