目录
- Cookie
- cookie是什么?
- javax.servlet.http.Cookie
- 获取与添加
- 示例:上次访问时间
- 示例:历史记录
- Session
- Session原理
- JSP默认内置session对象
- 获得Session
- API
- 示例:登录验证码
<一> Cookie
1> cookie是什么?
客户端技术,服务器将每个用户的数据以cookie的形式写给各自的浏览器;
- 会话级别cookie(MaxAge=-1)
- 本地cookie(MaxAge>0)
- 删除cookie(MaxAge=0)
2> javax.servlet.http.Cookie
名称必须遵守 RFC 2109。
这意味着它只能包含 ASCII 字母数字字符,不能包含逗号、分号或空格,也不能以 $ 字符开头;cookie 的名称在创建之后不得更改。
Cookie:
javax.servlet.http.Cookie
cookie值可以唯一标识客户端
每个web服务器20个cookie
总共300个cookie
每个cookie大小限定4K
new Cookie(String,String)
getName()
getValue(String)
ck.setPath("/");
*注意cookie保存的时间是访问当前Servlet的时间,与这里设置的Path无关,这里的Path只其携带作用
ck.setMaxAge(60*60*24);
3> 获取与添加
从请求中获取cookies + 将cookie返回给客户端
void addCookie(Cookie cookie)
HttpServletResponse
*响应消息头
Set-Cookie头字段
Cookie[] getCookies()
HttpServletRequest
4> 示例:上次访问时间
JDK1.8新时间类:https://blog.csdn.net/qq_42292831/article/details/105342748
package xyz.kuoa.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 测试cookie
* @author X
*
*/
public class ServletDemo1 extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
//获取cookie
Cookie[] cks = request.getCookies();
String time = "";
PrintWriter out = response.getWriter();
for (int i = 0; cks!=null&&i < cks.length; i++) {
if("lastAccessTime".equals(cks[i].getName())){
time = cks[i].getValue();
LocalDateTime tempTime = LocalDateTime.parse(time,DateTimeFormatter.ofPattern("yyyyMMddHHmmss"));
time = DateTimeFormatter.ofPattern("yyyy年MM月dd日 HH:mm:ss").format(tempTime);
out.print("你上次访问的时间为:"+time);
}
}
//写入cookie
//cookie参数只能为ASCII字母数字,不能有其他字符
String time1 = DateTimeFormatter.ofPattern("yyyyMMddHHmmss").format(LocalDateTime.now());
Cookie ck = new Cookie("lastAccessTime",time1);
//访问哪些路径时携带当前cookie(以该路径为前缀)
//注意cookie保存的时间是访问当前Servlet的时间,与这里设置的Path无关,这里的Path只其携带作用
//ck.setPath("/");
ck.setMaxAge(60*60*24);
response.addCookie(ck);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
5> 示例:历史记录
- Book.java
package xyz.kuoa.entity;
public class Book {
private String id;
private String name;
private double price;
private String author;
public Book(String id, String name, double price, String author) {
super();
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 double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
@Override
public String toString() {
return "Book [id=" + id + ", name=" + name + ", price=" + price + ", author=" + author + "]";
}
}
- DBUtils.java
package xyz.kuoa.util;
import java.util.HashMap;
import java.util.Map;
import xyz.kuoa.entity.Book;
public class DBUtils {
private static Map<String,Book> books = new HashMap<>();
static{
books.put("1", new Book("1","《时间简史》",89.9,"霍金"));
books.put("2", new Book("2","《C语言入门》",75.9,"小A"));
books.put("3", new Book("3","《Java入门》",52.9,"小B"));
books.put("4", new Book("4","《C#入门》",53.9,"小C"));
books.put("5", new Book("5","《PHP入门》",64.9,"小D"));
}
public static Map<String, Book> findAllBooks() {
return books;
}
public static Book findBookById(String id){
return books.get(id);
}
}
- ServletDemo1.java
package xyz.kuoa.history;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;
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 xyz.kuoa.entity.Book;
import xyz.kuoa.util.DBUtils;
public class ServletDemo1 extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.print("本网站书籍列表:<br/>");
Map<String, Book> books = DBUtils.findAllBooks();
for (Map.Entry<String, Book> b : books.entrySet()) {
out.print("<a href='" + request.getContextPath() + "/servlet/showBookDetail?id=" + b.getKey()
+ "' target='_blank'>" + b.getValue().getName() + "<a><br/>");
}
out.print("<hr/>您浏览过的书籍列表:<br/>");
Cookie[] cookies = request.getCookies();
String idString = "";
for (int i = 0; cookies!=null&&i < cookies.length; i++) {
if("historyBookId".equals(cookies[i].getName())){
idString = cookies[i].getValue();
String[] ids = idString.split("-");
for (String id : ids) {
String name = DBUtils.findBookById(id).getName();
out.print(name+"<br/>");
}
break;
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
- ShowBookDetail.java
package xyz.kuoa.history;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
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 xyz.kuoa.entity.Book;
import xyz.kuoa.util.DBUtils;
public class ShowBookDetail extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
// 显示图书的详细信息
// 获得get方式提交的ID
String id = request.getParameter("id");
Book book = DBUtils.findBookById(id);
out.print(book + "<br/>");
// 把当前浏览过得书籍ID写回到客户端
String historyBookId = organizeId(id, request);
Cookie ck = new Cookie("historyBookId", historyBookId);
ck.setPath("/");
//ck.setMaxAge(60 * 60 * 24);
response.addCookie(ck);
}
private String organizeId(String id, HttpServletRequest request) {
String idString = "";
Cookie[] cookies = request.getCookies();
for (int i = 0; cookies != null && i < cookies.length; i++) {
if ("historyBookId".equals(cookies[i].getName())) {
idString = cookies[i].getValue();
break;
}
}
if (idString == "") {
idString = id;
} else {
idString = id+"-"+idString;
// 去重
String[] ids = idString.split("-");
List<String> list = new LinkedList<>();
Collections.addAll(list, ids);
for (int i = 0; i < list.size(); i++) {
for (int j = i + 1; j < list.size(); j++) {
if (list.get(i).equals(list.get(j))) {
list.remove(j);
j--;
}
}
}
idString = "";
for (int i = 0; i < list.size(); i++) {
if(i==0){
idString = list.get(i);
}else{
idString = idString+"-"+list.get(i);
}
}
}
return idString;
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
<二> Session
☞ 浏览器关闭后一个会话(Session)结束:每个浏览器维护一个会话;
☞ 为什么要使用Session:
- session是服务端技术,维护自身域对象,同一会话下,一个应用可共享数据;
- 域对象值可以为Object,cookie只能为String(ASCII字母数字字符)
1> Session原理
Session底层依赖cookie
2> JSP默认内置session对象
3> 获得Session
HttpSession session = request.getSession();
session.setAttribute("A","AAA");
String a = (String)session.getAttribute("A");
3> API
- void setAttribute(String, Object)
- Object getAttribute(String)
- void removeAttribute(String)
- 获得保存在cookie中的id
- session.getId();
- 设置过期时间
- session.setMaxInactiveInterval(60);
- 立马销毁session
- session.invalidate();
☞ 另一种设置session过期时间的方式(web.xml):
<!-- 单位:分钟 --> <session-config> <session-timeout>10</session-timeout> </session-config>
4> 示例:登录验证码
https://kylee.blog.csdn.net/article/details/106403717