java - Spring Boot Web中的AOP不生效

1.问题描述
我想在一个Spring MVC Controller运行前插入一个切面，在控制台显示Hello index（index是注入切面的方法名称）。但是访问页面调用控制器的时候失败了。在切面配置类加入断点，接着DEBUG，显示访问页面的时候，切面配置类甚至都没有运行，三段代码如下，您能帮我看一看问题所在吗？
2.代码如下：
(1)入口类：

@SpringBootApplication
@EnableAspectJAutoProxy
public class Demo3Application {

    public static void main(String[] args) {
        SpringApplication.run(Demo3Application.class, args);
        System.out.println("start!");
    }
}

(2)切面配置类

@Aspect
@Component
public class HelloAspect {
    @Before(value = "execution(String cn.shaytang.HelloController.index())")
    public void before(JoinPoint joinPoint){
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        Method method = methodSignature.getMethod();
        System.out.println("Hello" + method.getName());
    }
}

(3)加入切面的控制器

@Controller
public class HelloController {
    @RequestMapping(value = "")
    String index(){
        return "index";
    }
}

3.控制台结果

start!
2016-04-26 00:08:07.500  INFO 4302 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2016-04-26 00:08:07.500  INFO 4302 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2016-04-26 00:08:07.516  INFO 4302 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 15 ms