OncePerRequestFilter过滤器

过滤器在请求到达目标资源之前或响应返回客户端之前对请求或响应进行拦截和处理，OncePerRequestFilter过滤器逻辑在一次完整的HTTP请求中仅执行一次，即使请求在服务器内部经过了多次转发（forward）或包含多个资源请求。

OncePerRequestFilter的使用

public class DemoFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        String url = request.getRequestURI();
        System.out.println("----->过滤器开始处理请求"+url);
        long startTime = System.currentTimeMillis();
        filterChain.doFilter(request,response);
        long timeTaken = System.currentTimeMillis()  - startTime;
        System.out.println("<-----过滤器处理结束，url:"+url+"耗时："+timeTaken);
    }
}

注册OncePerRequestFilter

@Configuration
public class FilterConfig {

    @Bean
    public FilterRegistrationBean<DemoFilter> registrationBean(){
        System.out.println("过滤器生成范围");
        FilterRegistrationBean<DemoFilter> registrationBean = new FilterRegistrationBean<>();
        registrationBean.setFilter(new DemoFilter());
        //设置过滤器生成范围
        registrationBean.addUrlPatterns("/*");
        //过滤器名称
        registrationBean.setName("demoFilter");
        //设置优先级
        registrationBean.setOrder(1);
        return registrationBean;
    }
}