拦截器和过滤器

关于过滤器和拦截器，一直容易混乱，小记一下。

对比

Filter是servlet的规范，是web三大组件之一（Servlet，Filter，Listener），不依赖于spring；
拦截器是一些框架中的概念，比如：Spring，用于拦截请求和响应的处理过程。拦截器通常是在Spring MVC的上下文中使用的，提供了对控制器（Controller）方法的拦截能力
过滤器和拦截器功能类似，都是对请求预处理和拦截，
都是链式的，Filter没有执行chain.doFilter或者拦截器的prehandler没有返回true，请求不再继续传递。

过滤器

在spring中，过滤器可以通过继承OncePerRequestFilter

java 复制代码

@Order(998)
@Component
public class MyFilter01 extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        System.out.println("自定义Filter01");
        filterChain.doFilter(request,response);
    }
}

实现源生Filter

java 复制代码

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.UUID;
public class TraceIdFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 初始化代码（如果需要）
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;

        String traceId = httpRequest.getHeader("Trace-ID");
        if (traceId == null || traceId.isEmpty()) {
            traceId = UUID.randomUUID().toString();
        }
        TraceIdHolder.setTraceId(traceId);
        httpResponse.setHeader("Trace-ID", traceId);

        try {
            chain.doFilter(request, response);
        } finally {
            TraceIdHolder.clear();
        }
    }
    @Override
    public void destroy() {
        // 销毁代码（如果需要）
    }
}

// 注册
@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean<TraceIdFilter> traceIdFilter() {
        FilterRegistrationBean<TraceIdFilter> registrationBean = new FilterRegistrationBean<>();
        registrationBean.setFilter(new TraceIdFilter());
        registrationBean.addUrlPatterns("/*"); // 过滤所有路径
        return registrationBean;
    }
}

拦截器

拦截器可以实现HandlerInterceptor接口（需要注册）

java 复制代码

//定义
public class MyInterceptor01 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("自定义拦截器01");
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}
// 注册
@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor02()).order(667);
        registry.addInterceptor(new MyInterceptor01()).order(666);
    }
}