Interceptor拦截器

Interceptor介绍

拦截器(Interceptor)同 Filter 过滤器一样，它俩都是面向切面编程——AOP 的具体实现（AOP切面编程只是一种编程思想而已）。

你可以使用 Interceptor 来执行某些任务，例如在 Controller 处理请求之前编写日志，添加或更新配置......

在 Spring中，当请求发送到 Controller 时，在被Controller处理之前，它必须经过 Interceptors（0或更多）。

Spring Interceptor是一个非常类似于Servlet Filter 的概念 。

过滤器和拦截器的区别

对于过滤器和拦截器的区别：

• 过滤器（Filter）：当你有一堆东西的时候，你只希望选择符合你要求的某一些东西。定义这些要求的工具，就是过滤器。
• 拦截器（Interceptor）：在一个流程正在进行的时候，你希望干预它的进展，甚至终止它进行，这是拦截器做的事情。

自定义 Interceptor

如果你需要自定义 Interceptor 的话必须实现 org.springframework.web.servlet.HandlerInterceptor接口并且需要重写下面下面3个方法：

public boolean preHandle(HttpServletRequest request,
                         HttpServletResponse response,
                         Object handler)
 
 
public void postHandle(HttpServletRequest request,
                       HttpServletResponse response,
                       Object handler,
                       ModelAndView modelAndView)
 
 
public void afterCompletion(HttpServletRequest request,
                            HttpServletResponse response,
                            Object handler,
                            Exception ex)

注意： preHandle方法返回 true或 false。如果返回 true，则意味着请求将继续到达 Controller 被处理。

配置Interceptor

配置拦截器，需要实现WebMvcConfigurer并重写addInterceptors方法

@Component
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {

       registry.addInterceptor(firstInterceptor).addPathPatterns("/api/*");

    }

案例

创建拦截器

• FirstInterceptor:拦截所有请求
• SecondInterceptor:拦截所有请求
• OldLoginInterceptor:拦截/api/oldLogin请求

FirstInterceptor

@Component
public class FirstInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("FirstInterceptor-prehandle-进入");
        System.out.println("FirstInterceptor-prehandle-请求uri:"+request.getRequestURI());
        request.setAttribute("start",System.currentTimeMillis());

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("FirstInterceptor-postHandle-进入");
        System.out.println("FirstInterceptor-postHandle-请求uri:"+request.getRequestURI());

        Long start= (Long) request.getAttribute("start");
        Long end=System.currentTimeMillis();
        System.out.println("请求执行时间："+(end-start));
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
        System.out.println("FirstInterceptor-afterCompletion-进入");

    }
}

SecondInterceptor

@Component
public class SecondInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("SecondInterceptor-prehandle-进入");
        System.out.println("SecondInterceptor-prehandle-请求uri:"+request.getRequestURI());

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("SecondInterceptor-postHandle-进入");
        System.out.println("SecondInterceptor-postHandle-请求uri:"+request.getRequestURI());
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("SecondInterceptor-afterCompletion-进入");
        System.out.println("SecondInterceptor-postHandle-请求uri:"+request.getRequestURI());
    }
}

OldLoginInterceptor

/**
 * 如果你请求的地址是 /api/oldLogin 则跳转到 /api/login
 */
@Component
public class OldLoginInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("OldLoginInterceptor-prehandle-进入");
        System.out.println("OldLoginInterceptor-prehandle-请求uri:"+request.getRequestURI());
        response.sendRedirect("/api/login");

        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("OldLoginInterceptor-postHandle-进入");
        System.out.println("OldLoginInterceptor-postHandle-请求uri:"+request.getRequestURI());
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("OldLoginInterceptor-afterCompletion-进入");
        System.out.println("OldLoginInterceptor-afterCompletion-请求uri:"+request.getRequestURI());
    }
}

配置拦截器

@Data
@Component
public class WebConfig implements WebMvcConfigurer {

    private final FirstInterceptor firstInterceptor;
    private final SecondInterceptor secondInterceptor;
    private final OldLoginInterceptor oldLoginInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(firstInterceptor).addPathPatterns("/api/*");
        registry.addInterceptor(secondInterceptor).addPathPatterns("/api/*");
        registry.addInterceptor(oldLoginInterceptor).addPathPatterns("/api/oldLogin");
    }
}

测试拦截器

@RestController
@RequestMapping("/api")
public class HelloController {

    @RequestMapping("/hello")
    public Object hello() throws InterruptedException {
        Thread.sleep(2000);
        return "hello";
    }

    @RequestMapping("/login")
    public Object login()  {
        return "login page";
    }

    @RequestMapping("/oldLogin")
    public Object oldLogin() {
        return "oldLogin page";
    }
}

源码地址 (opens new window)