javaweb用户验证码登录session例子

package com.dp.javaweb.Servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.Arrays; import java.util.LinkedList; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.dp.javaweb.Bean.Book; import com.dp.javaweb.Bean.BookDtatbase; import com.dp.javaweb.Constant.Costant; public class ShowBooksAll extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out=response.getWriter(); //显示书籍的详细内容 String id=request.getParameter("id"); Book book=BookDtatbase.findBookId(id); out.write(book.toString()); //向客户端写回bookhistory名字的Cookie String ids=makeIds(request,id); Cookie c=new Cookie(Costant.BOOK_HISTORY, ids); c.setMaxAge(60*60); c.setPath(request.getContextPath()); response.addCookie(c); } //组织ID情况分析 // 原有的cookie中的id 当前新访问的书的id 应该写回的id //a、Cookie[] cs为null 1 bookHistory=1 //b、没有bookHistory的cookie 1 bookHistory=1 //c、1 2 bookHistory=2-1 //d、2-1 1 bookHistory=1-2 //e、1-2 3 bookHistory=3-1-2 //f、1-2-3 2 bookHistory=2-1-3 //g、2-1-3 4 bookHistory=4-2-1 private String makeIds(HttpServletRequest request, String id) { Cookie cs[]=request.getCookies(); //a情况 if(cs==null){ return id; } //b情况 Cookie cookie=null; for(Cookie c:cs){ if(Costant.BOOK_HISTORY.equals(c.getName())){ cookie=c; break; } } //cdefg String ids[]=cookie.getValue().split("\\-"); //用linkedlist就可以做这种方式的添加与删除 LinkedList<String> list=new LinkedList<String>(Arrays.asList(ids)); //cde if(list.size()<3){ if(list.contains(id)){ list.remove(id); } list.addFirst(id); }else{//fg if(list.contains(id)){ list.remove(id); }else{ list.remove(id); } list.addFirst(id); } StringBuffer sb=new StringBuffer(); for(int i=0;i<list.size();i++){ if(i>0){ sb.append("-"); } sb.append(list.get(i)); } return sb.toString(); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }