电商网站中我的足迹/浏览历史实现关键代码

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.oraclewdp.utils.ConvertUtil;

@WebServlet(name="history",urlPatterns="/history")
public class HistoryAction extends HttpServlet {
@Override
public void init() throws ServletException {
super.init();
}
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String producthistoryid="";
String id=req.getParameter("id");
//获取Cookie数据并遍历，看是否已经存在producthistoryid这个Cookie
Cookie[] cookies=req.getCookies();
if(cookies!=null&&cookies.length>0){
for (Cookie cookie : cookies) {
String name=cookie.getName();
String value=cookie.getValue();
if(name.equals("producthistoryid")){
//存在producthistoryid这个cookie的话，就将它赋值给producthistoryid这个变量
producthistoryid=value;
}
}
}
//当遍历=之后发现没有这个Cookie是，就创建producthistoryid这个Cookie，并将商品id保存到其中
if(producthistoryid==null||producthistoryid.equals("")){
id+=",";
System.out.println(id);
Cookie producthistoryCookie=new Cookie("producthistoryid",id);
resp.addCookie(producthistoryCookie);
}else{
//存在producthistoryid这个Cookie时，就将最近浏览的id添加到字符串的最前面
//要保证最新浏览的商品id在最前面，有两种实现方式，当最下面哪种更简便
//方式一：
//			String historyid="";
//			List<String> maskList=new ArrayList<String>();
//			String[] masks=producthistoryid.split(",");
//			for (String mask: masks){
//				if(!mask.equals(id)){
//					maskList.add(mask);
//				}
//			}
//         //ConvertUtil是将ArrayList里面的内容转换成字符串的一个帮助类
//			String rs=ConvertUtil.convertByMask(maskList, ",");
//			rs=id+","+rs;
//或者这样实现，三行代码就可以搞定
producthistoryid=","+producthistoryid;
producthistoryid=producthistoryid.replace(","+id+",", ",");
String rs=id+producthistoryid;

Cookie producthistoryCookie=new Cookie("producthistoryid",rs);
resp.addCookie(producthistoryCookie);
}
resp.sendRedirect(req.getContextPath()+"/productList");
}
@Override
public void destroy() {
super.destroy();
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
super.doGet(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
super.doPost(req, resp);
}
public HistoryAction() {
super();
}

}