@WebServlet("/cdiservlet")      
public class NewServlet extends HttpServlet {
    private Message message;

    @Override             ||重寫doGet方法
    public void init() {
        message = new MessageB();    ||對message初始化
    }

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws IOException {              ||拋出可能出現IO異常
        response.getWriter().write(message.get());   ||捕獲可能發生的異常
    }
}
 

public interface Message {         ||servlet實現Message接口的一個對象實例
    public String get();
}

public class MessageB implements Message {          ||servlet創建以下對象的實例
    public MessageB() { }

    @Override
    public String get() {
        return "message B";
    }
}

@WebServlet("/cdiservlet")              ||使用CDI，servlet聲明它對Message
 
實例的依賴性，並讓它由CDI運行時自動註入
public class NewServlet extends HttpServlet {
    @Inject private Message message;

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws IOException {       ||拋出可能出現IO異常

          response.getWriter().write(message.get());  ||捕獲可能發生的異常
 
 }
}

剖析servlet injection及源碼分析.