REST Api中Filter、Interceptor、AOP的

filter过滤器：过滤器始于servlet，依赖servlet，主要应用于用户访问权限、记录访问轨迹日志。

Interceptor拦截器：拦截器是基于java的反射机制，可以知晓要访问的contoller和方法。

AOP：Spring两大核心之一，可以获取访问的controller、方法和参数，但是获取不到请求头中的信息，主要应用于系统日志的记录。

三者同时存在于项目中，执行顺序为：filter、Interceptor、ControllerAdvice、Aspect、controller

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基于spring boot框架REST拦截使用

Filter

之前提到过过滤器依赖于servlet容器，其运行原理与servlet类似，若想使用过滤器必须实现Filter接口，重写doFilter方法。Filter提供的方法有三个init、doFilter、destroy。

创建的TimeFilter主要是重写doFilter规定TimeFilter需要干哪些事情！

package com.per.web.filter;

import java.io.IOException;
import java.util.Date;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;


//@Component 
public class TimeFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("初始化filter");

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        Long strat = new Date().getTime();
        System.out.println("start filter");
        chain.doFilter(request, response);
        Long finish = new Date().getTime();
        System.out.println("finish filter"+(finish-strat));
    }

    @Override
    public void destroy() {
        System.out.println("销毁filter");
    }

}

WebConfig文件调用TimeFilter，并设定对哪些url的那种格式做过滤！

package com.per.web.config;

import java.util.ArrayList;
import java.util.List;

//import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
//import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

//import com.per.web.Interceptor.TimeInterceptor;
import com.per.web.filter.TimeFilter;

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter{
//  @Autowired
//  TimeInterceptor timeInterceptor;
//
//  @Override
//  public void addInterceptors(InterceptorRegistry registry) {
//      registry.addInterceptor(timeInterceptor);
//  }
    
    @Bean
    public FilterRegistrationBean timeFilter() {
        FilterRegistrationBean filterRegistrationBean =new FilterRegistrationBean();
        TimeFilter timeFilter =new TimeFilter();
        filterRegistrationBean.setFilter(timeFilter);
        
        List<String> urList =new ArrayList<String>();
        urList.add("/*");
        filterRegistrationBean.setUrlPatterns(urList);
        return filterRegistrationBean;
    }
}

---

Interceptor

拦截器需要实现HandlerInterceptor接口，重写里面的三种方法，preHandle、postHandle、afterCompletion。
preHandle：在拦截某个controller之前执行。
postHandle：在执行完controller之后不抛出异常的情况下执行。
afterCompletion：在执行完controller之后无论是否发生异常都会执行。

TimeInterceptor实现HandlerInterceptor接口。

/**
 * 
 */
package com.per.web.Interceptor;

import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

/**
 * @author Administrator
 *
 */
@Component
public class TimeInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        // 在调用某个controller之前执行
        System.out.println("preHandle");
        
        System.out.println(((HandlerMethod)handler).getBean().getClass().getName());
        
        System.out.println(((HandlerMethod)handler).getMethod().getName());
        
        request.setAttribute("stratTime", new Date().getTime());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        // 在调用某个controller之后执行，且在不抛出异常的情况下
        System.out.println("postHandle");
        Long stratTime=  (Long)request.getAttribute("stratTime");
        request.setAttribute("控制层执行耗时：",(new Date()).getTime()-stratTime);
        System.out.println("=================拦截器耗时："+(Long)request.getAttribute("控制层执行耗时："));

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        // 执行controller之后执行，无论是否抛出异常
        System.out.println("afterCompletion");
        Long stratTime=  (Long)request.getAttribute("stratTime");
        request.setAttribute("控制层执行耗时：",(new Date()).getTime()-stratTime);
        System.out.println("ex============"+ex);

    }

}

配置文件注入TimeInterceptor，使用WebMvcConfigurerAdapter中的拦截器适配器添加该拦截器。

package com.per.web.config;

//import java.util.ArrayList;
//import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
//import org.springframework.boot.web.servlet.FilterRegistrationBean;
//import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import com.per.web.Interceptor.TimeInterceptor;
//import com.per.web.filter.TimeFilter;

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter{
    @Autowired
    TimeInterceptor timeInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(timeInterceptor);
    }
    
//  @Bean
//  public FilterRegistrationBean timeFilter() {
//      FilterRegistrationBean filterRegistrationBean =new FilterRegistrationBean();
//      TimeFilter timeFilter =new TimeFilter();
//      filterRegistrationBean.setFilter(timeFilter);
//      
//      List<String> urList =new ArrayList<String>();
//      urList.add("/*");
//      filterRegistrationBean.setUrlPatterns(urList);
//      return filterRegistrationBean;
//  }
}

拦截器会拦截所有controller层，无论是自己写的还是spring提供的！！！

---

AOP

设置切点，前置、后置、增强

package com.per.web.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class TimeAspect {
    @Around("execution(* com.per.web.controller.UserController.*(..))")
    public Object handleControllerMethod(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("切面编程开始！");
        Object[] listObject=pjp.getArgs();
        for(Object obj:listObject){
            System.out.println("obj is============================"+obj);//遍历出执行的方法所有参数
        }
        
        Object obj=pjp.proceed();//执行切片
        System.out.println(obj);//获取执行的方法
        System.out.println("切面编程结束！");
        return obj;
    }
}

注意三个注解缺一不可，@Aspect、@Component、@Around(或@Before或After)