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

@Order(998)
@Component
public class MyFilter01 extends OncePerRequestFilter {@Overrideprotected 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

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 {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {// 初始化代码（如果需要）}@Overridepublic 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();}}@Overridepublic void destroy() {// 销毁代码（如果需要）}
}// 注册
@Configuration
public class FilterConfig {@Beanpublic 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）

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