SpringBoot拦截器以及源码详析

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 {
        // 获取请求路径
        String requestUrl = request.getRequestURI();
        log.info("请求的路径是: {}", requestUrl);

        String username = request.getParameter("username");
        if (username != null) {
            // 放行
            return true;
        }

        request.setAttribute("msg", "请先登录");
        // 携带msg跳转到登录页
        request.getRequestDispatcher("/").forward(request, response);
        return false;
    }

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

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

import com.codeliu.interceptor.LoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorReGIStry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

// 表示这是一个配置类
@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
    // 遍历拦截器
    for (int i = 0; i < this.interceptorList.size(); i++) {
        HandlerInterceptor interceptor = this.interceptorList.get(i);
        // 执行当前拦截器的preHandle方法
        if (!interceptor.preHandle(request, response, this.handler)) {
            // 如果preHandle方法返回为false，则执行当前拦截器的afterCompletion方法
            triggerAfterCompletion(request, response, null);
            return false;
        }
        // 记录当前拦截器的下标
        this.interceptorIndex = i;
    }
    return true;
}

void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex) {
    // 反向遍历拦截器
    for (int i = this.interceptorIndex; i >= 0; i--) {
        HandlerInterceptor interceptor = this.interceptorList.get(i);
        try {
            // 执行当前拦截器的afterCompletion方法
            interceptor.afterCompletion(request, response, this.handler, ex);
        }
        catch (Throwable ex2) {
            logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
        }
    }
}

// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

mappedHandler.applyPostHandle(processedRequest, response, mv);

void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
    throws Exception {
	// 反向遍历
    for (int i = this.interceptorList.size() - 1; i >= 0; i--) {
        HandlerInterceptor interceptor = this.interceptorList.get(i);
        // 执行当前拦截器的postHandle方法
        interceptor.postHandle(request, response, this.handler, mv);
    }
}

processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);