关于java 的安全访问这块ClassLoader, SecurityManager

ClassLoader, SecurityManager

private void checkPackageAccess(Class cls, ProtectionDomain pd) {
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
    final String name = cls.getName();
            final int i = name.lastIndexOf('.');
    if (i != -1) {
                AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
        sm.checkPackageAccess(name.substring(0, i));
        return null;
                    }
                }, new AccessControlContext(new ProtectionDomain[] {pd}));
    }
}
domains.add(pd);
    }