1 会话技术
1. 会话:一次会话中包含多次请求和响应。
* 一次会话:浏览器第一次给服务器资源发送请求,会话建立,直到有一方断开为止
2. 功能:在一次会话的范围内的多次请求间,共享数据
3. 方式:
1. 客户端会话技术:Cookie
2. 服务器端会话技术:Session
2 Cookie
概念:客户端会话技术,将数据保存到客户端
快速入门:
* 使用步骤:
1. 创建Cookie对象,绑定数据
* new Cookie(String name, String value)
2. 发送Cookie对象
* response.addCookie(Cookie cookie)
3. 获取Cookie,拿到数据
* Cookie[] request.getCookies()
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
@WebServlet("/cookieDemo1")
public class CookieDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
Cookie c
= new Cookie("msg", "hello");
response
.addCookie(c
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
@WebServlet("/cookieDemo2")
public class CookieDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
Cookie
[] cs
= request
.getCookies();
if(cs
!= null
){
for (Cookie c
: cs
) {
String name
= c
.getName();
String value
= c
.getValue();
System
.out
.println(name
+ ":" + value
);
}
}
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
实现原理
* 基于响应头set-cookie和请求头cookie实现
cookie的细节
1. 一次可不可以发送多个cookie?
* 可以
* 可以创建多个Cookie对象,使用response调用多次addCookie方法发送cookie即可。
2. cookie在浏览器中保存多长时间?
1. 默认情况下,当浏览器关闭后,Cookie数据被销毁
2. 持久化存储:
* setMaxAge(int seconds)
1. 正数:将Cookie数据写到硬盘的文件中。持久化存储。并指定cookie存活时间,时间到后,cookie文件自动失效
2. 负数:默认值
3. 零:删除cookie信息
3. cookie能不能存中文?
* 在tomcat 8 之前 cookie中不能直接存储中文数据。
* 需要将中文数据转码---一般采用URL编码(%E3)
* 在tomcat 8 之后,cookie支持中文数据。特殊字符还是不支持,建议使用URL编码存储,URL解码解析
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
@WebServlet("/cookieDemo3")
public class CookieDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
Cookie c1
= new Cookie("msg2", "hello2");
Cookie c2
= new Cookie("name", "zhangsan");
response
.addCookie(c1
);
response
.addCookie(c2
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
@WebServlet("/cookieDemo4")
public class CookieDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
Cookie c1
= new Cookie("msg", "setMaxAge");
c1
.setMaxAge(0);
response
.addCookie(c1
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
Cookie的特点和作用
1. cookie存储数据在客户端浏览器
2. 浏览器对于单个cookie 的大小有限制(4kb) 以及 对同一个域名下的总cookie数量也有限制(20个)
* 作用:
1. cookie一般用于存出少量的不太敏感的数据
2. 在不登录的情况下,完成服务器对客户端的身份识别
3 cookie共享问题?
1. 假设在一个tomcat服务器中,部署了多个web项目,那么在这些web项目中cookie能不能共享?
* 默认情况下cookie不能共享
* setPath(String path):设置cookie的获取范围。默认情况下,设置当前的虚拟目录
* 如果要共享,则可以将path设置为"/"
2. 不同的tomcat服务器间cookie共享问题?
* setDomain(String path):如果设置一级域名相同,那么多个服务器之间cookie可以共享
* setDomain(".baidu.com"),那么tieba.baidu.com和news.baidu.com中cookie可以共享
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
@WebServlet("/cookieDemo5")
public class CookieDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
Cookie c1
= new Cookie("msg", "你好");
c1
.setPath("/");
response
.addCookie(c1
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
4 案例:记住上一次访问时间
1. 需求:
1. 访问一个Servlet,如果是第一次访问,则提示:您好,欢迎您首次访问。
2. 如果不是第一次访问,则提示:欢迎回来,您上次访问时间为:显示时间字符串
2. 分析:
1. 可以采用Cookie来完成
2. 在服务器中的Servlet判断是否有一个名为lastTime的cookie
1. 有:不是第一次访问
1. 响应数据:欢迎回来,您上次访问时间为:2018年6月10日11:50:20
2. 写回Cookie:lastTime=2018年6月10日11:50:01
2. 没有:是第一次访问
1. 响应数据:您好,欢迎您首次访问
2. 写回Cookie:lastTime=2018年6月10日11:50:01
package cn
.ys
.cookie
;
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 java
.io
.IOException
;
import java
.net
.URLDecoder
;
import java
.net
.URLEncoder
;
import java
.text
.SimpleDateFormat
;
import java
.util
.Date
;
@WebServlet("/cookieTest")
public class CookieTest extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
response
.setContentType("text/html;charset=utf-8");
Cookie
[] cookies
= request
.getCookies();
boolean flag
= false;
if(cookies
!= null
&& cookies
.length
> 0){
for (Cookie cookie
: cookies
) {
String name
= cookie
.getName();
if("lastTime".equals(name
)){
flag
= true;
Date date
= new Date();
SimpleDateFormat sdf
= new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
String str_date
= sdf
.format(date
);
System
.out
.println("编码前:" + str_date
);
str_date
= URLEncoder
.encode(str_date
, "utf-8");
System
.out
.println("编码后:" + str_date
);
cookie
.setValue(str_date
);
cookie
.setMaxAge(60 * 60 * 24 * 30);
response
.addCookie(cookie
);
String value
= cookie
.getValue();
System
.out
.println("解码前:" + value
);
value
= URLDecoder
.decode(value
, "utf-8");
System
.out
.println("解码后:" + value
);
response
.getWriter().write("<h1>欢迎回来,您上次访问时间为:" + value
+ "</h1>");
break;
}
}
}
if(cookies
== null
|| cookies
.length
== 0 || flag
== false){
Date date
= new Date();
SimpleDateFormat sdf
= new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
String str_date
= sdf
.format(date
);
System
.out
.println("编码前:" + str_date
);
str_date
= URLEncoder
.encode(str_date
, "utf-8");
System
.out
.println("编码后:" + str_date
);
Cookie cookie
= new Cookie("lastTime", str_date
);
cookie
.setMaxAge(60 * 60 * 24 * 30);
response
.addCookie(cookie
);
response
.getWriter().write("<h1>您好,欢迎您首次访问</h1>");
}
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
5 Session
概念:服务器端会话技术,在一次会话的多次请求间共享数据,将数据保存在服务器端的对象中。HttpSession
快速入门:
1. 获取HttpSession对象:
HttpSession session = request.getSession();
2. 使用HttpSession对象:
Object getAttribute(String name)
void setAttribute(String name, Object value)
void removeAttribute(String name)
原理
* Session的实现是依赖于Cookie的。
细节:
1. 当客户端关闭后,服务器不关闭,两次获取session是否为同一个?
* 默认情况下。不是。
* 如果需要相同,则可以创建Cookie,键为JSESSIONID,设置最大存活时间,让cookie持久化保存。
Cookie c = new Cookie("JSESSIONID",session.getId());
c.setMaxAge(60*60);
response.addCookie(c);
2. 客户端不关闭,服务器关闭后,两次获取的session是同一个吗?
* 不是同一个,但是要确保数据不丢失。tomcat自动完成以下工作
* session的钝化:
* 在服务器正常关闭之前,将session对象系列化到硬盘上
* session的活化:
* 在服务器启动后,将session文件转化为内存中的session对象即可。
3. session什么时候被销毁?
1. 服务器关闭
2. session对象调用invalidate() 。
3. session默认失效时间 30分钟
选择性配置修改
<session-config>
<session-timeout>30</session-timeout>
</session-config>
session的特点
1. session用于存储一次会话的多次请求的数据,存在服务器端
2. session可以存储任意类型,任意大小的数据
6 session与Cookie的区别
1. session存储数据在服务器端,Cookie在客户端
2. session没有数据大小限制,Cookie有
3. session数据安全,Cookie相对于不安全
package cn
.ys
.session
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.HttpServlet
;
import javax
.servlet
.http
.HttpServletRequest
;
import javax
.servlet
.http
.HttpServletResponse
;
import javax
.servlet
.http
.HttpSession
;
import java
.io
.IOException
;
@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
HttpSession session
= request
.getSession();
session
.setAttribute("msg", "hello session");
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
package cn
.ys
.session
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.HttpServlet
;
import javax
.servlet
.http
.HttpServletRequest
;
import javax
.servlet
.http
.HttpServletResponse
;
import javax
.servlet
.http
.HttpSession
;
import java
.io
.IOException
;
@WebServlet("/sessionDemo2")
public class SessionDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
HttpSession session
= request
.getSession();
Object msg
= session
.getAttribute("msg");
System
.out
.println(msg
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
package cn
.ys
.session
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.*
;
import java
.io
.IOException
;
@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
HttpSession session
= request
.getSession();
System
.out
.println(session
);
Cookie c
= new Cookie("JSESSIONID", session
.getId());
c
.setMaxAge(60*60);
response
.addCookie(c
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
package cn
.ys
.session
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.*
;
import java
.io
.IOException
;
@WebServlet("/sessionDemo4")
public class SessionDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
HttpSession session
= request
.getSession();
System
.out
.println(session
);
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
7 案例:验证码
1. 案例需求:
1. 访问带有验证码的登录页面login.jsp
2. 用户输入用户名,密码以及验证码。
* 如果用户名和密码输入有误,跳转登录页面,提示:用户名或密码错误
* 如果验证码输入有误,跳转登录页面,提示:验证码错误
* 如果全部输入正确,则跳转到主页success.jsp,显示:用户名,欢迎您
package cn
.ys
.servlet
;
import javax
.imageio
.ImageIO
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.HttpServlet
;
import javax
.servlet
.http
.HttpServletRequest
;
import javax
.servlet
.http
.HttpServletResponse
;
import java
.awt
.*
;
import java
.awt
.image
.BufferedImage
;
import java
.io
.IOException
;
import java
.util
.Random
;
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
int width
= 100;
int height
= 50;
BufferedImage image
= new BufferedImage(width
,height
,BufferedImage
.TYPE_INT_RGB
);
Graphics g
= image
.getGraphics();
g
.setColor(Color
.PINK
);
g
.fillRect(0,0,width
,height
);
g
.setColor(Color
.BLUE
);
g
.drawRect(0,0,width
- 1,height
- 1);
String str
= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
Random ran
= new Random();
StringBuilder sb
= new StringBuilder();
for (int i
= 1; i
<= 4; i
++) {
int index
= ran
.nextInt(str
.length());
char ch
= str
.charAt(index
);
sb
.append(ch
);
g
.drawString(ch
+"",width
/5*i
,height
/2);
}
String checkCode_session
= sb
.toString();
request
.getSession().setAttribute("checkCode_session",checkCode_session
);
g
.setColor(Color
.GREEN
);
for (int i
= 0; i
< 10; i
++) {
int x1
= ran
.nextInt(width
);
int x2
= ran
.nextInt(width
);
int y1
= ran
.nextInt(height
);
int y2
= ran
.nextInt(height
);
g
.drawLine(x1
,y1
,x2
,y2
);
}
ImageIO
.write(image
,"jpg",response
.getOutputStream());
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
,response
);
}
}
package cn
.ys
.servlet
;
import javax
.servlet
.ServletException
;
import javax
.servlet
.annotation
.WebServlet
;
import javax
.servlet
.http
.HttpServlet
;
import javax
.servlet
.http
.HttpServletRequest
;
import javax
.servlet
.http
.HttpServletResponse
;
import javax
.servlet
.http
.HttpSession
;
import java
.io
.IOException
;
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
request
.setCharacterEncoding("utf-8");
String username
= request
.getParameter("username");
String password
= request
.getParameter("password");
String checkCode
= request
.getParameter("checkCode");
HttpSession session
= request
.getSession();
String checkCode_session
= (String
) session
.getAttribute("checkCode_session");
session
.removeAttribute("checkCode_session");
if(checkCode_session
!= null
&& checkCode_session
.equalsIgnoreCase(checkCode
)){
if("zhangsan".equals(username
) && "123".equals(password
)){
session
.setAttribute("user",username
);
response
.sendRedirect(request
.getContextPath()+"/success.jsp");
}else{
request
.setAttribute("login_error","用户名或密码错误");
request
.getRequestDispatcher("/login.jsp").forward(request
,response
);
}
}else{
request
.setAttribute("cc_error","验证码错误");
request
.getRequestDispatcher("/login.jsp").forward(request
,response
);
}
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login
</title>
<script>
window.onload = function(){
document.getElementById("img").onclick = function(){
this.src="/day16/checkCodeServlet?time="+new Date().getTime();
}
}
</script>
<style>
div{
color: red;
}
</style>
</head>
<body>
<form action="/day16/loginServlet" method="post">
<table>
<tr>
<td>用户名
</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码
</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td>验证码
</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/day16/checkCodeServlet"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"></td>
</tr>
</table>
</form>
<div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%>
</div>
<div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %>
</div>
</body>
</html>
success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title
</title>
</head>
<body>
<h1><%=request.getSession().getAttribute("user")%>,欢迎您
</h1>
</body>
</html>