Instantiate an object of a class managed by Spring

You need to access the ApplicationContext of Spring in some way. As you said that this class is not managed by the same, I think you will have to instantiate it:

ApplicationContext context = new ClassPathXmlApplicationContext("resources/spring.xml");

or if you are in a HttpServlet:

WebApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(getServletContext());

It will depend on the context of your application. Once you have context , getting an instance is simple:

SuaClasse instancia = context.getBean(SuaClasse.class);