javaee(cookie和session)
cookie记录最后浏览时间
@WebServlet(urlPatterns = "/demo1")
public class demo1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/css; charset=utf-8");
PrintWriter writer = resp.getWriter();
//获取客户端最后访问时间
Cookie[] cookies = req.getCookies();
for(int i=0;cookies!=null&&i则需要maxAge,以秒为单位时间，最大值设0则是命令浏览器删除该cookie。
注意！！！
上下文中的不同地址的cookie是可以访问的，但前提是访问的路径以cookie的path开始的路径，浏览器就带，否则不带。
如果想让上下文都可以访问cookie，则使用cookie.setPath（"/上下文名称"）,来设置为顶层的cookie
ck.setPath("/上下文名称");//低级
ck.setPath(req.getContextPath());//中级 上下文名称
ck.setPath("/");//高级 这个和上面等同，当前上下文的名称保存用户名
js网页 在jsp获得cookie和在获取cookie后checked保持选择状态
Title
<%Cookie[] c=request.getCookies();
String name="";
String checked="";
for(int i=0;c!=null&&i
@WebServlet(urlPatterns = "/cookie1")
public class CookieDemo1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html;charset=UTF-8");
PrintWriter writer = resp.getWriter();
String name = req.getParameter("name");
String pwd = req.getParameter("pwd");
String remember = req.getParameter("remember");
Cookie ck=new Cookie("user",name);
ck.setPath("/");
if("tom".equals(name)&&"123".equals(pwd)){
//表单类型不输入是空字符串，但是复选框和单选按钮不选是null
if(remember!=null){
ck.setMaxAge(Integer.MAX_VALUE);
}else{
ck.setMaxAge(0);
}
resp.addCookie(ck);
writer.write("登录成功！");
}else{
writer.write("登录失败");
//设置两秒跳到重新登录
resp.setHeader("refresh","2;url="+req.getContextPath()+"/denglu.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
//实体类（书）public class Book {
private String id;
private String name;
private String price;
private String author;
public Book(String id, String name, String price, String author) {
this.id = id;
this.name = name;
this.price = price;
this.author = author;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
}public class DBUtil {
private static Map books=new HashMap<>();
static {
books.put("1",new Book("1","java编程思想","20","小明"));
books.put("2",new Book("2","java深入虚拟机","25","小明"));
books.put("3",new Book("3","java设计模式","10","小明"));
books.put("4",new Book("4","java并发","10","小明"));
books.put("5",new Book("5","python编程","10","小明"));
}
//获取所有的书map类型
public static Map getBooks(){
return books;
}
//获取指定的书 根据id
public static Book findBook(String id){
return books.get(id);
}
} @WebServlet(urlPatterns = "/showBook")
public class ShowAllBookServlet extends HttpServlet {
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req,resp);
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setContentType("text/html;charset=UTF-8");
Map books = DBUtil.getBooks();
PrintWriter writer = resp.getWriter();
writer.write("本网站的有以下的好书：
");
for (Map.Entry book:books.entrySet()) {
writer.write(""+book.getValue().getName()+"
");
}
writer.write("
你最近浏览过的书有：
");
Cookie[] ck = req.getCookies();
for(int i=0;i @WebServlet(urlPatterns = "/findBook")
public class findBook extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
//获取get提交id参数
String id = request.getParameter("id");
Book book = DBUtil.findBook(id);
PrintWriter writer = response.getWriter();
writer.write("书籍名称:" + book.getName() + "
");
writer.write("书籍价格:" + book.getPrice() + "
");
writer.write("书籍作者:" + book.getAuthor() + "
");
//把当前浏览过的书写会回到客户端
String historyBook = organzeId(id, request);
Cookie ck = new Cookie("historyBookId", historyBook);
ck.setPath("/");
ck.setMaxAge(Integer.MAX_VALUE);
response.addCookie(ck);
}
/**
* 没有cookie 把当前的id给添加进去
* 有cookie，但是没有historyBookId 把当前的id给添加进去
* historyBookId 2
*/
private String organzeId(String id, HttpServletRequest request) {
Cookie[] cookies = request.getCookies();
if (cookies == null) {
//如果没有cookies就直接返回当前id
return id;
}
//查找cookies名字是historyBookId的
Cookie historyBookId = null;
for (int i = 0; i < cookies.length; i++) {
if("historyBookId".equals(cookies[i].getName())){
historyBookId=cookies[i];
}
}
if(historyBookId==null){
return id;
}
//不管存储几个
String value = historyBookId.getValue();
String[] values = value.split("-");
LinkedList ls = new LinkedList<>(Arrays.asList(values));
//历史记录最多保持3个(队列 先进先出)
if(ls.size()<3){
//如果浏览记录里面有重复的id就删除掉。
if(ls.contains(id)){
ls.remove(id);
}
}else{
//超过3个就浏览记录就删除最后一个或者包含的id
if(ls.contains(id)){
ls.remove(id);
}else{
ls.removeLast();
}
}
ls.addFirst(id);//添加到最前面
StringBuffer sb = new StringBuffer();
for (int i=0;i0){
sb.append("-");
}
sb.append(ls.get(i));
}
return sb.toString();
}
}
HttpSession对象原理
1.获取名称为JSESSIONID的cookie的值
2.没有这样的cookie,创建一个新的session对象，分配唯一的SessionId，并且向客户端写一个名字叫JSESSION=sessionID的cookie
3.有这个样的Cookie,获取cookie的值，从服务器内存中根据ID找那个session对象。
HttpSession对象状态
出生request.getSession();
活着：应用运行时
搁置：内存溢出，服务器重启，会在tomcat目录的work下持久化，等启动服务器后，session就自动的回调进内存（放心大胆的重启服务器，不用担心session的丢失）
持久化：存盘，IO实现serializable
死亡：超时，默认30分钟，setMaxInactiveInterval(int);
Session,invalidate()；强制销毁
在xml中配置
session是一个域对象,可以存储对象
getId()获取对象，setMaxInactiveInterval（int ）设置session存活时间，秒做单位
invalidate()使得会话无效
cookie客户端技术，只能存取字符串
客户端禁用Cookie后回话数据保存问题
解决方案：
1.在主页上给出提示，请不要禁用cookie。
2.URL重写。必需对网站的所有地址都重写。(刷新会有问题)
http://url -->http://url;JSESSIONID=111
response.encodeURL（String url）;//前提写上request.getSession()不然没用作用
看到浏览有没有发送cookie请求的消息头，没有就重写URL，有就不重写。