SpringMVC拦截器

SpringMVC拦截器

拦截器介绍

  1. 拦截器同过滤器一样,都是面向切面编程—AOP的具体实现,符合横切关注点的功能都可以考虑使用AOP实现;
  2. 可以使用Interceptor来执行某些任务,例如在Controller处理请求之前编写日志,添加或配置更新配置;
  3. 在Spring中,当请求发送到Controller处理之前,他必须经过Interceptor(0个或多个);

拦截器作用

  • 日志记录:记录请求信息的日志,以便进行信息监控,信息统计等等;
  • 权限检查:如登录检测,进入处理器检测是否登录;
  • 性能监控:通过拦截器在进入处理器之前记录开始时间,在处理完后记录结束时间,从而得到该请求的处理时间;
  • 通用行为:读取Cookie得到用户信息并将用户对象放入请求,只要是多个处理器都需要的即可使用拦截器实现;
package com.kuangstudy.config.handler;

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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

@Slf4j
public class LoginInterceptor implements HandlerInterceptor {


    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("1-----preHandle----->");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("3-----postHandle----->");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("4-----afterCompletion----->");
    }
}



package com.kuangstudy.config.mvc;

import com.kuangstudy.config.handler.LoginInterceptor;
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.WebMvcConfigurer;

@Configuration
public class WebMvcConfiguration implements WebMvcConfigurer {


    @Bean
    // 初始化拦截器放入到ioc容器中
    public LoginInterceptor getLoginInterceptor(){
        return new LoginInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry
                // 1： 拦截器注册
                .addInterceptor(getLoginInterceptor())
                // 2: 给拦截器配置并且定义规则
                .addPathPatterns("/api/**");
    }
}

拦截器链の执行顺序

根据配置的先后顺序执行preHandler, postHandle和afterCompletion则相反

多拦截器执行流程

自定义拦截器

这是SpringMVC的拦截器

  1. 自定义拦截器必须实现HandlerInterceptor接口或者继承HandlerInterceptorAdapter类,并且重写三个方法:

    • preHandler
      在目标Handler方法执行前执行; 返回true执行目标方法, 返回false阻止目标方法
    • postHandler
      在目标Handler方法执行后,视图生成前执行;
    • afterCompletion
      在目标Handler方法执行后,视图生成后执行;

    preHandler -(判断逻辑写在preHandler )-> Handler –> postHandler –> 视图 –> afterCompletion

  2. 创建一个SpringMVC的拦截器的配置类实现WebMvcConfigurer的接口,并且重写addInterceptors()方法,注册拦截器类,并且为当前拦截器类定义规则;

  3. 可以在xml配置配置拦截方式;

具体实现举例

LogInterceptor类:

public class LogInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        long startTime = System.currentTimeMillis();
        System.out.println("\n-------- LogInterception.preHandle --- ");
        System.out.println("Request URL: " + request.getRequestURL());
        System.out.println("Start Time: " + System.currentTimeMillis());

        request.setAttribute("startTime", startTime);

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("\n-------- LogInterception.postHandle --- ");
        System.out.println("Request URL: " + request.getRequestURL());
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("\n-------- LogInterception.afterCompletion --- ");

        long startTime = (Long) request.getAttribute("startTime");
        long endTime = System.currentTimeMillis();
        System.out.println("Request URL: " + request.getRequestURL());
        System.out.println("End Time: " + endTime);

        System.out.println("Time Taken: " + (endTime - startTime));
    }
}

OldLoginInterceptor 类：

public class OldLoginInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("\n-------- OldLoginInterceptor.preHandle --- ");
        System.out.println("Request URL: " + request.getRequestURL());
        System.out.println("Sorry! This URL is no longer used, Redirect to /admin/login");
		// 在控制层之前,所有请求都进入这里,被重定向到/admin/login
        response.sendRedirect(request.getContextPath()+ "/admin/login");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("\n-------- OldLoginInterceptor.postHandle --- ");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("\n-------- OldLoginInterceptor.afterCompletion --- ");
    }
}

配置拦截器:

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LogInterceptor());

        registry.addInterceptor(new OldLoginInterceptor()).addPathPatterns("/admin/oldLogin");

        registry.addInterceptor(new AdminInterceptor()).addPathPatterns("/admin/*").excludePathPatterns("/admin/oldLogin");
    }
}

解析:

	LogInterceptor 拦截器用于拦截所有请求； 
	OldLoginInterceptor 用来拦截链接 “ / admin / oldLogin”，它将重定向到新的 “ / admin / login”。；
	AdminInterceptor用来拦截链接 “/admin/*”，除了链接 “ / admin / oldLogin”。

自定义Controller验证拦截器

@Controller
public class LoginController {

    @RequestMapping("/index")
    public String index(Model model){
        return "index";
    }

    @RequestMapping(value = "/admin/login")
    public String login(Model model){
        return "login";
    }
}

登录检测

流程:

  1. 访问需要登录的资源时,由拦截器重定向到登录页面;
  2. 如果访问的是登录页面,拦截器不应该拦截;
  3. 用户登录成功后,往Cookie/session中添加登录成功的标识(如用户编号);
  4. 下次请求时,拦截器通过判断Cookie/session中是否有该标识来决定继续流程还是到登录页面;
  5. 在此拦截器还应该允许游客访问的资源(看具体业务需要);
public class MyInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        boolean flag = true;
        String ip = request.getRemoteAddr();
        long startTime = System.currentTimeMillis();
        request.setAttribute("requestStartTime", startTime);
        if (handler instanceof ResourceHttpRequestHandler) {
            System.out.println("preHandle这是一个静态资源方法！");
        } else if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            Method method = handlerMethod.getMethod();
            System.out.println("用户:" + ip + ",访问目标:" + method.getDeclaringClass().getName() + "." + method.getName());
        }

        //如果用户未登录
        User user = (User) request.getSession().getAttribute("user");
        if (null == user) {
            //重定向到登录页面
            response.sendRedirect("toLogin");
            flag = false;
        }
        return flag;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        if (handler instanceof ResourceHttpRequestHandler) {
            System.out.println("postHandle这是一个静态资源方法！");
        } else if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            Method method = handlerMethod.getMethod();
            long startTime = (long) request.getAttribute("requestStartTime");
            long endTime = System.currentTimeMillis();
            long executeTime = endTime - startTime;

            int time = 1000;
            //打印方法执行时间
            if (executeTime > time) {
                System.out.println("[" + method.getDeclaringClass().getName() + "." + method.getName() + "] 执行耗时 : "
                        + executeTime + "ms");
            } else {
                System.out.println("[" + method.getDeclaringClass().getSimpleName() + "." + method.getName() + "] 执行耗时 : "
                        + executeTime + "ms");
            }
        }
    }

}
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