(1)显示书名列表,及最近阅读的最多三本书的书名
public class ShowGoods extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 978235855242977508L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
PrintWriter writer = resp.getWriter();
writer.write("所有的书籍是:");
writer.write("</br>");
for( Entry<String, MyBook> entry: OfferMap.getBookInfo().entrySet()){
writer.write("<a href = '"+req.getContextPath()+"/ShowGoodsDetails?id="+entry.getKey()+"'>"+entry.getValue().getName()+"</a>");
writer.write("</br>");
}
writer.write("最近浏览的三本书是:");
writer.write("</br>");
Cookie[] cookies = req.getCookies();
if(cookies != null)
for(Cookie cookie : cookies){
if("lastVisitBook".equals(cookie.getName()) && cookie.getValue() != null){
String[] ids = cookie.getValue().split(",");
for(String id : ids){
writer.write("<a href = '"+req.getContextPath()+"/ShowGoodsDetails?id="+id+"'>"+OfferMap.getBookInfo().get(id).getName()+"</a>");
writer.write("</br>");
}
}
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
super.doPost(req, resp);
}
}
(2)显示书籍的详细信息,并将阅览的书名信息存到cookie中
public class ShowGoodsDetails extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = -46163301904321918L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
LinkedHashMap<String, MyBook> map = OfferMap.getBookInfo();
PrintWriter writer = resp.getWriter();
String id = req.getParameter("id");
if(id != null){
MyBook myBook = map.get(id);
writer.write(myBook.getName()+"的详细信息是:");
writer.write("</br>");
writer.print("ID是:"+myBook.getId()+"<br/>");
writer.print("书本名是:"+myBook.getName()+"<br/>");
writer.print("书本价格是:"+myBook.getPrice()+"<br/>");
}
LinkedList<String> list = new LinkedList<>();
StringBuffer sb = new StringBuffer();
Cookie[] cookies = req.getCookies();
boolean flag = false;
if(cookies != null){
for(Cookie cookie : cookies){
if("lastVisitBook".equals(cookie.getName()) && cookie.getValue() != null){
String[] ids = cookie.getValue().split(",");
for(String idname : ids){
list.add(idname);
}
//1、如果list中已经有3个,那么删除第一个,(存在一种情况,那就是原先已经有的三个里,这次又重复点击了,那么正常情况下,其位置应该需要变动)
if(list.size() >= 3){
list.removeFirst();
list.addLast(id);
}else {
//2、如果list中不足3个,不是最后一个,那么就放在后边一个
list.add(id);
}
for(String name : list){
sb.append(name+",");
}
flag = true;
}
}
if(flag){
sb = sb.deleteCharAt(sb.length()-1);
Cookie[] cookiess = req.getCookies();
for(Cookie cookie : cookiess){
if("lastVisitBook".equals(cookie.getName()) && cookie.getValue() != null){
cookie.setValue(sb.toString());
}
}
//putCookieToResp(resp,sb.toString());
}else {
putCookieToResp(resp,sb.append(id).toString());
}
}else {
putCookieToResp(resp,sb.append(id).toString());
}
}
private void putCookieToResp(HttpServletResponse resp, String string) {
Cookie cookie = new Cookie("lastVisitBook", string);
cookie.setMaxAge(3600*24*30);
cookie.setPath("/webAndAjax");
//cookie.setDomain("localhost");
resp.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// TODO Auto-generated method stub
super.doPost(req, resp);
}
}
出现的问题:
一开始的时候,在原来有cookie的情况下,修改原来cookie内容的时候,使用的是new的方法,然后在显示时,一直只显示初始cookie的key值对应的内容。
经过查询资料, Cookie不仅仅有名字和值两个属性,还有域(domain),过期时间(expires),路径(path)等属性。其中,不同的域、不同的路径下可以存在同样名字的cookie。可以推测,相同路径和域下不能存在两个相同key值的cookie,所以,new两次,系统在获取的时候,第二次new的会出现错乱,而导致不能获取正确的cookie内容。
解决方法:采用 cookie 值修改的方式。