June 11, 2008

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Today I had to solve an unusual problem: I needed to find the directory that was used to load a specific Java .class file (the location in the file system of given .class file). I needed it because I wanted to load resources located somewhere in the classPath with file access API (not with accessable as streams). I needed something like getClass().getResourceAsStream() but for a directory.

The first idea I had was to use the following code:

URL url = getClass().getResource(".");

This works well in a console application but in a servlet container (e.g. in Tomcat or in GWT shell) it runs differently.

Later I found on the net a really nice solution:

URL classesRootDir = getClass().getProtectionDomain().getCodeSource().getLocation();

The above returns the base directory used when loading your .class files. It does not contain the package. It contains the classpath directory only. For example, in a console application the above returns someting like this:

file:/C:/Documents%20and%20Settings/Administrator/workspace/TestPrj/bin/

In a Web application it returns someting like this:

file:/C:/Tomcat/webapps/MyApp/WEB-INF/classes/

It also works well for GWT applications running in hosted mode in GWT shell and in a compiled mode in JBoss. This was the real solution.

Tags: application, class, File, getresourceasstream, GWT, java file, java url, language java, shell, source language