java过滤器中Filter的ChainFilter过滤链

package servlet; 

import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/**
* urlPattern={"/*"}获取所有的Servlet的映射路径，实现不同Servlet之间的交互
*/
@WebServlet(name = "DemoFilter",urlPatterns = {"/*"})
public class DemoFilter implements Filter{
/**
* 过滤器的初始化方法
* @param filterConfig 可以获取部署描述符文件(web.xml)中分配的过滤器初始化参数。
* @throws ServletException
*/
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("过滤器被创建了");
}/**
*
* @param servletRequest 请求
* @param servletResponse 响应
* @param filterChain 链条，对过滤器进行阻止和放行
* @throws IOException
* @throws ServletException
*/
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
System.out.println("过滤器被执行了");
servletResponse.setContentType("text/html,charset=utf-8");
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
response.addHeader("Access-Control-Allow-Origin","*");
String referer = request.getHeader("referer");
System.out.println(referer);
filterChain.doFilter(servletRequest,servletResponse);//放行
}@Override
public void destroy() {
System.out.println("过滤器被销毁了");
}
}