source: src/main/java/geniusweb/partiesserver/jarClassLoader1.java@ 2

package geniusweb.partiesserver;

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.jar.Attributes;

/**
 * Classloader that ensures loaded code is kept separate from other loaded code.
 * This is to prevent dependency conflicts between parties that we  load.
 *
 */
class JarClassLoader1 extends URLClassLoader {

        private URL u;

        public JarClassLoader1(URL url, ClassLoader parent) {
                super(new URL[] { url }, parent);
                this.u = url;

                String filename = url.getPath();
                if (filename.startsWith("file:")) {
                        filename = filename.substring(5);
                }
                if (filename.endsWith("/")) {
                        filename = filename.substring(0, filename.length() - 1);
                }
                if (filename.endsWith("!")) {
                        filename = filename.substring(0, filename.length() - 1);
                }

                File jarfile = new File(filename);

                if (jarfile == null || !jarfile.exists()) {
                        throw new IllegalArgumentException(
                                        "file does not exist:" + jarfile);
                }
                if (!jarfile.canRead()) {
                        throw new IllegalArgumentException(
                                        "File " + jarfile + " has no read permissions");
                }
                if (!jarfile.isFile() || !jarfile.getName().endsWith(".jar")) {
                        throw new IllegalArgumentException("File " + jarfile
                                        + " must be a file and have extension .jar");

                }

        }

        public String getMainClassName() throws IOException {
                JarURLConnection uc = (JarURLConnection) u.openConnection();
                Attributes attr = uc.getMainAttributes();
                return attr != null ? attr.getValue(Attributes.Name.MAIN_CLASS) : null;
        }
}