init:該方法是對filter對象進行初始化的方法，僅在容器初始化filter對象結(jié)束后被調(diào)用一次，參數(shù)FilterConfig可以獲得filter的初始化參數(shù)；
doFilter:可以對request和response進行<u>預(yù)處理</u>。其中FilterChain可以將處理后的request和response對象傳遞到過濾鏈上的下一個資源。
destroy():該方法在容器銷毀對象前被調(diào)用。

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

@Component
public class LogFilter implements Filter {

    private static final Logger LOG = LoggerFactory.getLogger(LogFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // 打印請求信息
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        LOG.info("------------- LogFilter 開始 -------------");
        LOG.info("請求地址: {} {}", request.getRequestURL().toString(), request.getMethod());
        LOG.info("遠(yuǎn)程地址: {}", request.getRemoteAddr());

        long startTime = System.currentTimeMillis();
        filterChain.doFilter(servletRequest, servletResponse);
        LOG.info("------------- LogFilter 結(jié)束 耗時：{} ms -------------", System.currentTimeMillis() - startTime);
    }
}

結(jié)果

總結(jié)

1.過濾器用來實現(xiàn)通用的功能，減少代碼冗余，提高可維護性；

2.一個過濾器可以配置給多個資源使用（編碼過濾器）；

3.一個資源也可以配置多個過濾器，按照配置順序調(diào)用。

攔截器的方式

如果不懂請先看了介紹再來

攔截器的介紹

話不說多直接上代碼

創(chuàng)建攔截器

/**
 * 攔截器：Spring框架特有的，常用于登錄校驗，權(quán)限校驗，請求日志打印 /login
 * @author : look-word
 * 2022-06-26 13:55
 **/
@Component
public class LogInterceptor implements HandlerInterceptor {
    private static final Logger LOG = LoggerFactory.getLogger(LogInterceptor.class);

        
    @Override
     public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
         // 打印請求信息
         LOG.info("------------- LogInterceptor 開始 -------------");
         LOG.info("請求地址: {} {}", request.getRequestURL().toString(), request.getMethod());
         LOG.info("遠(yuǎn)程地址: {}", request.getRemoteAddr());

         long startTime = System.currentTimeMillis();
         request.setAttribute("requestStartTime", startTime);
         return true;
     }

     @Override
     public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
         long startTime = (Long) request.getAttribute("requestStartTime");
         LOG.info("------------- LogInterceptor 結(jié)束 耗時：{} ms -------------", System.currentTimeMillis() - startTime);
     }
}

注冊攔截器

把我們的攔截器注冊到攔截器鏈中

/**
 * @author : look-word
 * 2022-06-26 14:03
 **/
@Configuration
public class SpringMvcConfig implements WebMvcConfigurer {

    @Resource
    private LogInterceptor logInterceptor;
    /**
     * 注冊攔截器
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry
                .addInterceptor(logInterceptor)
                .addPathPatterns("/**")// 對那些接口攔截
                .excludePathPatterns("/login");// 對哪些接機口放行
        WebMvcConfigurer.super.addInterceptors(registry);
    }
}

測試結(jié)果