@WebServlet("/cdiservlet") \\url映射
public class NewServlet extends HttpServlet {
    private Message message;
    @Override \\重写doGet方法
    public void init() {
        message = new MessageB();    ||对message初始化
    }
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws IOException { \\抛出可能出现IO异常
        response.getWriter().write(message.get()); \\捕获可能发生的异常
    }
}
public interface Message { \\servlet实现Message接口的一个对象实例
    public String get();
}
public class MessageB implements Message { \\servlet创建对象的实例
    public MessageB() { }
    @Override
    public String get() {
        return "message B";
    }
}
@WebServlet("/cdiservlet") \\使用CDI,servlet声明它对Message实例的依赖性,并让它由CDI运行时自动注入
public class NewServlet extends HttpServlet {
    @Inject private Message message;
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
                  throws IOException { \\抛出可能出现的IO异常
          response.getWriter().write(message.get()); \\捕获可能发生的异常
 }
}
原文:https://www.cnblogs.com/XZY30/p/10666152.html