过滤器

@WebFilter("/*")
public class File implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("初始化过滤器");
}

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    System.out.println("执行过滤器");
    // TODO
    filterChain.doFilter(servletRequest,servletResponse);（必写，不写的话有可能会报错）
}

public void destroy() {
    System.out.println("销毁过滤器");
}

}