java内部重定向死循环检例子

package org.fielter.test; import java.io.IOException; import java.util.ArrayList; import java.util.List; 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; /** * 过滤形成环路的fielter <p> * * @author yuezhen */ public class CircleFilter implements Filter { private List<String> l =new ArrayList<String>(); public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) { try{ boolean circle=false; HttpServletRequest req = (HttpServletRequest) request; List<String> list =new ArrayList<String>(); // 从request中取出list if(req.getAttribute("circle.finder.forward.list")!=null){ list=(List<String>)req.getAttribute("circle.finder.forward.list"); }else{ //list为null表明是初次的请求，获取原始的请求来源 ，并放入list list.add((String)req.getAttribute("javax.servlet.forward.request_uri")); } // 如果原始请求地址和需要跳转的地址一致，抛出异常 if(list.contains(req.getRequestURI())){ circle=true; } // 将本次需要forward的路径放入list，并保存 list.add(req.getRequestURI()); req.setAttribute("circle.finder.forward.list", list); // 用System.out来代替log System.out.println(""); System.out.println("[info] ==========================================="); System.out.println("[info] "+list); System.out.println("[info] ==========================================="); if(circle){ System.out.println("[error] find circle"); // 清空list req.removeAttribute("circle.finder.forward.list"); l=list; // 可以选择抛出异常，或者用其他的处理方式 throw new Exception(); } filterChain.doFilter(request, response); }catch(Exception e){ // 发现了重定向的死循环的后续处理 try { // 页面显示发现死循环 response.getOutputStream().print("has circle,the cytle is : "+l.toString()); } catch (IOException e1) { e1.printStackTrace(); } } } public void destroy() { } }