springboot-监听器，过滤器，拦截器，aop,自定义注解

springboot基础-监听器，过滤器，拦截器，aop,自定义注解

环境

idea2018，jdk1.8，

springboot版本：1.5.9.RELEASE

代码下载：
https://github.com/2010yhh/springBoot-demos.git
测试:启动项目后，访问：

  http://localhost:8080/springboot-demo2/test1
  http://localhost:8080//springboot-demo2/test2

1.监听器

listen的作用：可以在listen中完成一些如数据库、创建、数据库加载等一些初始化操作

@Component
public class StartApplicationListener implements ApplicationListener {
	public static AtomicInteger count=new AtomicInteger(0);
	 protected Logger log = LoggerFactory.getLogger(StartApplicationListener.class); 
	 private ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
	    @Override  
	    public void onApplicationEvent(ContextRefreshedEvent event) {  
	    	//防止重复执行
	    	 if (event.getApplicationContext().getParent() == null && count.incrementAndGet()<=1) {
	    		 //这里一个定时任务的初始化
	 	        this.service.scheduleAtFixedRate(new LogTask(),1000, 1000*60,TimeUnit.MILLISECONDS );
	 	        log.info("Listener系统配置加载完成...");  
	    	 }
	       
	    }  
}

2.过滤器

filter的作用：拦截请求，对请求或响应(Request、Response)统一设置，对请求、响应头加密、解密，对请求、响应压缩，过滤掉非法url，做网关转发等

@WebFilter(urlPatterns = "/test1/*", filterName = "indexFilter1")
@Order(Integer.MAX_VALUE-1)
public class MyFilter1 implements Filter {
	 protected Logger log = LoggerFactory.getLogger(MyFilter1.class);  
	@Override
	  public void destroy() {
		log.info("----->:indexFilter1 destroy method");
	  }
	  @Override
	  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
	      throws IOException, ServletException {
		  chain.doFilter(request, response);
		  log.info("----->:indexFilter1 doFilter method");
	  }
	  @Override
	  public void init(FilterConfig arg0) throws ServletException {
		  log.info("----->:indexFilter1 init method");
	  }
}

3.拦截器

拦截器作用：
* 作用于controller层,拦截到请求，对请求或响应(Request、Response)统一设置
* 进行逻辑判断，如用户是否已经登陆、有没有权限访问该页面等
和filter的作用有些类似，但二者又有不同的应用场景。

public class MyInterceptor implements HandlerInterceptor {
	 protected Logger log = LoggerFactory.getLogger(MyInterceptor.class);  
	//在请求处理之前进行调用（Controller方法调用之前
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
    	log.info("preHandle被调用");
        return true;    //如果false，停止流程，api被拦截
    }

    //请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
    	log.info("postHandle被调用");
    }

    //在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）
    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    	log.info("afterCompletion被调用");
    }

}

4.aop

aop的作用：横切面，代表的是一个普遍存在的与业务关系不大的却各个模块共有功能
* 横切关注点：经常发生在核心关注点的多处，而各处都基本相似。比如权限认证、日志、方法耗时
* 、事务处理

@Aspect  //声明切面
@Component  
public class LogAspect {  
	protected Logger log = LoggerFactory.getLogger(LogAspect.class);
	//定义横切点，标记方法
    @Pointcut("execution(* com.ctg.test.controller..*.*(..))")
    public void webLog(){}  
    //前置通知，切点之前执行
    @Before("webLog()")  
    public void deBefore(JoinPoint joinPoint) throws Throwable {  
        // 接收到请求，记录请求内容  
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();  
        HttpServletRequest request = attributes.getRequest();  
        // 记录下请求内容  
        log.info("URL : " + request.getRequestURL().toString());  
        log.info("HTTP_METHOD : " + request.getMethod());  
        log.info("IP : " + request.getRemoteAddr());  
        log.info("CLASS_METHOD : " + joinPoint.getSignature().getDeclaringTypeName() + "." + joinPoint.getSignature().getName());  
        log.info("ARGS : " + Arrays.toString(joinPoint.getArgs()));  
  
    }  
    //切点执行成功之后执行
    @AfterReturning(returning = "ret", pointcut = "webLog()")  
    public void doAfterReturning(Object ret) throws Throwable {  
        // 处理完请求，返回内容  
    	log.info("方法的返回值 : " + ret);  
    }  
  
    //后置异常通知，切点抛出异常后执行
    @AfterThrowing("webLog()")  
    public void throwss(JoinPoint jp){  
    	log.info("方法异常时执行.....");  
    }  
  
    //后置最终通知,final增强，不管是抛出异常或者正常退出都会执行；切点执行之后执行
    @After("webLog()")  
    public void after(JoinPoint jp){  
    	log.info("方法最后执行.....");  
    }  
}  

5.自定义注解

自定义注解可以避免代码的冗余，无侵害

@Retention(RetentionPolicy.RUNTIME)  
@Target(ElementType.METHOD)  
@Documented
@Inherited
public @interface MethodTime {
    //自定义属性
}