Java dynamic class loading fails on windows, but working fine on linux

Question

I am trying to load a class dynamically from a jar file. It worked fine on a Ubuntu linux box ( Sun Java Version 1.6.0_24 (b07).

When I tried to run the same thing on Windows (Windows 7, Java version "1.6.0_14") it fails with Class Not Found exception.

Following is code :

    try {
        String jarFile = "/sqljdbc4.jar";
        File newf = new File(jarFile);
        System.out.println(newf.getAbsolutePath());
        System.out.println("File exists ? :" + newf.exists());
        String urlPath = "jar:file://" + newf.getAbsolutePath() + "!/";
        System.out.println(urlPath);
        ClassLoader cur = Thread.currentThread().getContextClassLoader();

        URL[] jarUrlArray = { new URL(urlPath) };
        URLClassLoader cl = URLClassLoader.newInstance(jarUrlArray, cur);

        Class c = Class.forName(
                "com.microsoft.sqlserver.jdbc.SQLServerDriver", true, cl);
        Method m[] = c.getMethods();
        for (Method mm : m) {
            System.out.println(mm.getName());
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

While running on Linux, jar is placed at root and for Windows its at c:\ (source and binaries are in some folder on C:\ so "/sqljdbc4.jar" resolves to c:\sqljdbc4.jar on windows, I have made sure that correct jar location in passed to classloader for both the platforms.

Following is the stack trace i get on windows

java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.net.FactoryURLClassLoader.loadClass(URLClassLoader.java:594)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at DemoClass.loadAClass(DemoClass.java:31)
at DemoClass.main(DemoClass.java:14)

NOTE : You can use any jar that u have to try this out. I was playing with MS SQL Server JDBC Driver jar.

Thanks !

-Abhijeet.

Answer 1

Try using this to create the URL rather than manually building the string:

URL[] jarUrlArray = { newf.toURI().toURL() };