java加token实现单点登录

之前看过一些文章，直接说不清楚，因为我也是第一次研究单点登录，所有自己想写一篇希望能有所帮助

dome地址：

0.准备工作

1、tomcat8本地的安装

2、maven3本地的安装

3、使用maven发布项目到本地

1.简介
json web token(JWT)是一种新的用户认证方式,不同与以前的Session.

JWT不需要服务器端存储用户信息,当用户登录后,服务器将用户信息放入加密放入token（token会被客户端保存）,需要时再通过对token解密获取（客户请求时携带token）

2.代码
下面提供一种JWT的简单实现.这个例子实现的功能是:

1) 用户访问login.jsp进行登录操作.

则发放给用户本地浏览器的token为：eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiIxIiwiaWF0IjoxNTIyMjUzMTIwLCJzdWIiOiLmtYvor5XnlKjmiLcxIiwiZXhwIjoxNTIyMjUzNzIwfQ.5jWbc4yP11Qfz1T5HHAjFpgNWCtYyTwOmMB8rTZAY4s
2) 用户访问myServlet时,若用户已登录则跳转至info.jsp显示用户名,未登录则跳转至login.jsp.地址后面一定要有参数，不然是post请求
在token有效期间，再次访问http://localhost:8080/jwt_demo/Servlet/myServlet?1=1
进行一次get请求，返回正常

3)打开另外一个浏览器，也是用账号test1登录，登录成功之后转到第一个浏览器,继续执行http://localhost:8080/jwt_demo/Servlet/myServlet?1=1

因为在另外一个浏览器登录过了，所以发送请求肯定被拦截器拦截，跳到登录页面

4.直接上代码吧

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="Servlet/myServlet" method="post">
帐号:<input type="text" name="account">
密码:<input type="password" name="password">
<input type="submit" value="登录">
</form>
</body>
</html>

MyServlet.java

package com.hxuhao.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map.Entry;

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 javax.servlet.http.HttpSession;

import com.hxuhao.model.User;
import com.hxuhao.utils.JWTUtil;

import io.jsonwebtoken.Claims;

/**
* Servlet implementation class MyServlet
*/
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;

   private HashMap<Integer,User> users = new HashMap<>();

   @Override
   public void init() throws ServletException {
       super.init();
       users.put(Integer.valueOf(1), new User(1,"test1","123","测试用户1"));
       users.put(Integer.valueOf(2), new User(2,"test2","123","测试用户2"));
   }

/**
* @see HttpServlet#HttpServlet()
*/
public MyServlet() {
super();
}

/**
   * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
   */
   protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       request.setCharacterEncoding("utf-8");
       response.setCharacterEncoding("utf-8");
       if(request.getMethod().equals("POST")){
           doPost(request, response);
       }else{
           doGet(request, response);
       }
   }

/**
   * 查看信息
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response ) throws ServletException, IOException {
       //response.getWriter().append("Served at: ").append(request.getContextPath());
       HttpSession session = request.getSession();
       // 验证用户
       Cookie[] cookies = request.getCookies();
       //User user=null;
       String username = null;
       if(cookies!=null){
           for(int i=0;i<cookies.length;i++){
               System.out.println(cookies[i].getName() + " : " + cookies[i].getValue());
               String token = session.getAttribute("token").toString();
               //单点登录,取出每次登录保存的token，因为每次登录的token都是不一样的,如果客户端传过来的token可服务器取出来的token不一样
               //则已经登录过，退出登录
               //比如用户A在谷歌浏览器登录,保存的token是1234,A还没有退出,A一直访问后台带的token都是1234,A又在另外一个浏览器火狐登录这下token肯定又改变了
               //因为每次token都是加密的,这里使用session保存token，A在谷歌浏览器传过来的的token依然是1234,但是后台session保存的token在火狐浏览器登录之后
               //就改变了,取出浏览器发送请求带的token和session中的对比,如果一样调到登录页面,因为已经在另外一个浏览器登录。这就是单点登录
               if(!token.equals(cookies[i].getValue())){
                   System.out.println("单点登录");
                   request.getRequestDispatcher("../login.jsp").forward(request, response);
                   return;
               }
               if(cookies[i].getName().equals("JWT")){
                   Cookie cookie = cookies[i];
                   try {
                       // 检查token
                       Claims claims = JWTUtil.parseJWT(cookie.getValue());
                       username = claims.getSubject();
                       System.out.println("name : " + username);
                   } catch (Exception e) {
                       e.printStackTrace();
                   }
               }
           }
       }
       if(username!=null){
           request.setAttribute("username", username);
           request.getRequestDispatcher("../info.jsp").forward(request, response);
       }else{
           System.out.println("SendRedirect");
           response.sendRedirect("../login.jsp");
       }
   }

/**
   * 登录
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
       String account = request.getParameter("account");
       String password = request.getParameter("password");
       HttpSession session = request.getSession();
       System.out.println(account + " : " + password);
       String token = "";
       for(Entry<Integer, User> item : users.entrySet()){
           User u = item.getValue();
           //if条件写死代码做了授权,后期有时间可以配在web.xml中作授权认证
           if(u.getAccount().equals(account)
                   &&u.getPassword().equals(password)){
               try {
                   System.out.println(u.getName());
                   //将token 失效时间改为 60秒
                   token = JWTUtil.createJWT(String.valueOf(u.getId()), u.getName(), 1000*60);
                   session.setAttribute("token", token);
                   // 将token放进Cookie
                   Cookie cookie = new Cookie("JWT", token);
                   cookie.setPath("/");
                   // 设置cookie如果为负数，
// 该Cookie为临时Cookie，关闭浏览器即失效，浏览器也不会以任何形式保存该Cookie。
// 如果为0，表示删除该Cookie。默认为–1
                   cookie.setMaxAge(-1);
                   response.addCookie(cookie);
               } catch (Exception e) {
                   e.printStackTrace();
               }
           }
       }
       PrintWriter pw = response.getWriter();
       if(!token.equals("")){
           System.out.println(token);
           pw.print("login succeeded : " + token);
       }
       else{
           pw.print("login failed : error account or password");
       }
       pw.flush();
       pw.close();
   }

}
info.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h2>Hello,<%=request.getAttribute("username") %></h2>
</body>
</html>

JWTUtil.java

package com.hxuhao.utils;
import java.util.Date;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

public class JWTUtil {

private static final String profiles="hxhxhxhxh";

/**
* 由字符串生成加密key
* @return
*/
private static SecretKey generalKey(){
String stringKey = profiles;
byte[] encodedKey = Base64.decodeBase64(stringKey);
SecretKey key = new SecretKeySpec(encodedKey, 0, encodedKey.length, "AES");
return key;
}

/**
* 创建jwt
* @param id
* @param subject
* @param ttlMillis
* @return
* @throws Exception
*/
public static String createJWT(String id, String subject, long ttlMillis) throws Exception {
SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
long nowMillis = System.currentTimeMillis();
Date now = new Date(nowMillis);
SecretKey key = generalKey();
JwtBuilder builder = Jwts.builder()
.setId(id)
.setIssuedAt(now)
.setSubject(subject)
.signWith(signatureAlgorithm, key);
if (ttlMillis >= 0) {
long expMillis = nowMillis + ttlMillis;
Date exp = new Date(expMillis);
builder.setExpiration(exp);
}
return builder.compact();
}

/**
* 解析jwt
* @param jwt
* @return
* @throws Exception
*/
public static Claims parseJWT(String jwt) throws Exception{
SecretKey key = generalKey();
Claims claims = Jwts.parser()
.setSigningKey(key)
.parseClaimsJws(jwt).getBody();

return claims;
}
}

web.xml

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:web="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>myServlet</servlet-name>
<servlet-class>com.hxuhao.servlet.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>myServlet</servlet-name>
<url-pattern>/Servlet/myServlet</url-pattern>
</servlet-mapping>

</web-app>