五十、Filter过滤器,Interceptor拦截器，ControllerAdvice,Aspect切片

Filter过滤器,Interceptor拦截器，ControllerAdvice,Aspect切片

上图为在web项目中，在处理request请求时得处理顺序

在项目中我们改怎么使用呢？

Filter过滤器

/**
 * Created by GAOMINGQIAN on 2017/12/10.
 *<pr>
 *     Filter只能获取到请求的request和response。获取不到其他的信息
 *     因为Filter属于J2EE的内容，不知道spring
 *      会拦截所有的请求
 *</pr>
 *
 */
//@Component
public class TimeFilter implements Filter {
    //初始化的时候调用
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("time filter init");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("time filter start");
        long start=new Date().getTime();
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("time filter end:"+(new Date().getTime()-start));
        System.out.println("time filter finsh");
    }

    //销毁时调用
    @Override
    public void destroy() {
        System.out.println("time filter destory");
    }
}

上述内容中有一个@Component注解，当我们不想使用时或者更细的粒度拦截，需要在config类中进行注册

//配置一个过滤器
@Bean
public FilterRegistrationBean timeFilter() {
    //filter注册用的bean
    FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
    TimeFilter timeFilter = new TimeFilter();
    filterRegistrationBean.setFilter(timeFilter);
    List<String> urls = new ArrayList<>();
    urls.add("/*");
    //设置filter对那些请求有作用，这里设置的是对所有的请求都有作用
    filterRegistrationBean.setUrlPatterns(urls);
    return filterRegistrationBean;
}

Interceptor拦截器

/**
 * Created by GAOMINGQIAN on 2017/12/10.
 */
public class TimeInterceptor implements HandlerInterceptor {
    //该方法的返回值决定后续的方法是否执行(controller中的方法)
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("preHandle");
        //获取controller类名称
        System.out.println(((HandlerMethod) o).getBean().getClass().getName());
        //获取执行method的名字
        System.out.println(((HandlerMethod)o).getMethod().getName());
        httpServletRequest.setAttribute("startTime", new Date().getTime());
        return true;
    }

    //当controller抛出异常时，该方法不会被调用
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
        long start = (Long) httpServletRequest.getAttribute("startTime");
        System.out.println("time interceptor耗时" + (new Date().getTime() - start));
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("afterCompletion");
        long start = (Long) httpServletRequest.getAttribute("startTime");
        System.out.println("time interceptor耗时" + (new Date().getTime() - start));
        //当无异常的时候，e的值为null，有自定义异常时，也会为Null
        System.out.println(e);
    }
}

需要在配置类中声明才能使用，继承WebMvcConfigurerAdapter

//告诉spring这是一个配置类 
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter{
  
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
       //注册当前的拦截器
       registry.addInterceptor(new TimeInterceptor());
    }
}

Aspect切片使用

/**
 * Created by GAOMINGQIAN on 2017/12/10.
 */
@Aspect
@Component
public class TimeAspect {
   //around中的execution中的内容代表对哪些方法进行拦截
    @Around("execution(* study.security.web.controller.UserController.*(..))")
    public Object handlerControllerMethod(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("time aspect start");
        //获取执行方法的参数
        Object[] args = pjp.getArgs();
        long start = new Date().getTime();
        //执行拦截的方法  result为拦截方法的返回值
        Object result = pjp.proceed();
        System.out.println("time aspect 耗时：" + (new Date().getTime() - start));
        return result;
    }
}

ControllerAdvice，主要用于异常处理的控制器

/**
 * Created by GAOMINGQIAN on 2017/12/10.
 */
@ControllerAdvice
public class ControllerHandlerException {
    @ExceptionHandler(UserNotExistException.class)
    @ResponseBody
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    public Map<String, Object> handleUserNotExistException(UserNotExistException ex) {
        Map<String, Object> result = new HashedMap();
        //放置需要响应的内容
        result.put("message",ex.getMessage());
        return result;
    }
}

优缺点介绍：

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Filter过滤器：可以拿到request,response但是拿不到处理方法的信息

Interceptor拦截器：可以拿到request,response，也可以拿到处理方法的信息，但是拿不到处理方法参数的值

Aspect切片：可以拿到处理方法的所有信息，但是拿不到request,response

五十、Filter过滤器,Interceptor拦截器，ControllerAdvice,Aspect切片

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