为什么要告别session？有这样一个场景，系统的数据量达到千万级，需要几台服务器部署，当一个用户在其中一台服务器登录后，用session保存其登录信息，其他服务器怎么知道该用户登录了？（单点登录），当然解决办法有，可以用spring-session。如果该系统同时为移动端服务呢？移动端通过url向后台要数据，如果用session，通过sessionId识别用户，万一sessionId被截获了，别人可以利用sessionId向后台要数据，就有安全隐患了。所以有必要跟session说拜拜了。服务端不需要存储任何用户的信息，用户的验证应该放在客户端，jwt就是这种方式！
什么是jwt？
最详细的是官网：https://jwt.io/
这里以java的ssm框架为例，集成jwt。
1.pom.xml 导入jwt的包
<dependency> <groupId>com.auth0</groupId> <artifactId>java-jwt</artifactId> <version>2.2.0</version> </dependency>
2.编写jwt的工具类，有加密解密功能就好
import com.auth0.jwt.JWTSigner;import com.auth0.jwt.JWTVerifier;import com.auth0.jwt.internal.com.fasterxml.jackson.databind.ObjectMapper;import java.util.HashMap;import java.util.Map;public class JWT { private static final String SECRET = "XX#$%()(#*!()!KL<><MQLMNQNQJQK sdfkjsdrow32234545fdf>?N<:{LWPW"; private static final String EXP = "exp"; private static final String PAYLOAD = "payload"; public static <T> String sign(T object, long maxAge) { try { final JWTSigner signer = new JWTSigner(SECRET); final Map<String, Object> claims = new HashMap<String, Object>(); ObjectMapper mapper = new ObjectMapper(); String jsonString = mapper.writeValueAsString(object); claims.put(PAYLOAD, jsonString); claims.put(EXP, System.currentTimeMillis() + maxAge); return signer.sign(claims); } catch(Exception e) { return null; } } public static<T> T unsign(String jwt, Class<T> classT) { final JWTVerifier verifier = new JWTVerifier(SECRET); try { final Map<String,Object> claims= verifier.verify(jwt); if (claims.containsKey(EXP) && claims.containsKey(PAYLOAD)) { long exp = (Long)claims.get(EXP); long currentTimeMillis = System.currentTimeMillis(); if (exp > currentTimeMillis) { String json = (String)claims.get(PAYLOAD); ObjectMapper objectMapper = new ObjectMapper(); return objectMapper.readValue(json, classT); } } return null; } catch (Exception e) { return null; } }}
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3.jwt有了，ssm要如何去利用，用户验证的第一步是登录，登录时根据用户传来的username和password到数据库验证身份，如果合法，便给该用户jwt加密生成token
@RequestMapping(value="login", produces = "application/json; charset=utf-8") public @ResponseBody ResponseData login(HttpServletRequest request, @RequestParam( "email") String email, @RequestParam("password") String password) { Login login = new Login(); login.setEmail(email); login.setPassword(password); ResponseData responseData = ResponseData.ok(); Integer loginId = userService.checkLogin(login); if(null != loginId) { User user = userService.getUserByLoginId(loginId); login.setId(loginId); String token = JWT.sign(login, 60L* 1000L* 30L); responseData.putDataValue("loginId", login.getId()); responseData.putDataValue("token", token); responseData.putDataValue("user", user); } else{ responseData = ResponseData.customerError(); } return responseData; }
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4.在用户登录时，把loginId和token返回给前台，以后用户每次请求时，都得带上这两个参数，后台拿到token后解密出loginId，与用户传递过来的loginId比较，如果相同，则说明用户身份合法。因为是每个登录过后的每个请求，这里用springmvc的拦截器做
<mvc:interceptors> <mvc:interceptor> <mvc:mapping path="/**" /> <mvc:exclude-mapping path="/register" /> <mvc:exclude-mapping path="/login" /> <bean class="com.xforce.charles.interceptor.TokenInterceptor"></bean> </mvc:interceptor> </mvc:interceptors>
5.拦截器代码
import java.io.PrintWriter;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;import com.alibaba.fastjson.JSONObject;import com.xforce.charles.model.Admin;import com.xforce.charles.model.Login;import com.xforce.charles.util.JWT;import com.xforce.charles.util.ResponseData;public class TokenInterceptor implements HandlerInterceptor{ public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception arg3) throws Exception { } public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView model) throws Exception { } public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { response.setCharacterEncoding("utf-8"); String token = request.getParameter("token"); ResponseData responseData = ResponseData.ok(); if(null != token) { Login login = JWT.unsign(token, Login.class); String loginId = request.getParameter("loginId"); if(null != loginId && null != login) { if(Integer.parseInt(loginId) == login.getId()) { return true; } else{ responseData = ResponseData.forbidden(); responseMessage(response, response.getWriter(), responseData); return false; } } else { responseData = ResponseData.forbidden(); responseMessage(response, response.getWriter(), responseData); return false; } } else { responseData = ResponseData.forbidden(); responseMessage(response, response.getWriter(), responseData); return false; } } private void responseMessage(HttpServletResponse response, PrintWriter out, ResponseData responseData) { responseData = ResponseData.forbidden(); response.setContentType("application/json; charset=utf-8"); String json = JSONObject.toJSONString(responseData); out.print(json); out.flush(); out.close(); }}
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6.注意点：用@ResponseBody返回json数据时，有时会有乱码，需要在springmvc的配置文件里面加以下配置（spring4以上）
<mvc:annotation-driven> <mvc:message-converters register-defaults="true"> <bean class="org.springframework.http.converter.StringHttpMessageConverter"> <property name="supportedMediaTypes" value = "text/plain;charset=UTF-8" /> </bean> </mvc:message-converters> </mvc:annotation-driven>
7.最后分享一个类，用于返回给客户端的万能类，我觉得它可以满足一般的接口
import java.util.HashMap;import java.util.Map;public class ResponseData { private final String message; private final int code; private final Map<String, Object> data = new HashMap<String, Object>(); public String getMessage() { return message; } public int getCode() { return code; } public Map<String, Object> getData() { return data; } public ResponseData putDataValue(String key, Object value) { data.put(key, value); return this; } private ResponseData(int code, String message) { this.code = code; this.message = message; } public static ResponseData ok() { return new ResponseData(200, "Ok"); } public static ResponseData notFound() { return new ResponseData(404, "Not Found"); } public static ResponseData badRequest() { return new ResponseData(400, "Bad Request"); } public static ResponseData forbidden() { return new ResponseData(403, "Forbidden"); } public static ResponseData unauthorized() { return new ResponseData(401, "unauthorized"); } public static ResponseData serverInternalError() { return new ResponseData(500, "Server Internal Error"); } public static ResponseData customerError() { return new ResponseData(1001, "customer Error"); }}
