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
<!-- jwt -->
<!-- https://mvnrepository.com/artifact/com.auth0/java-jwt -->
<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";
//加密，传入一个对象和有效期
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;
}
}
//解密，传入一个加密后的token字符串和解密后的类型
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;
}
}
}
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
//处理登录
public
Login login = new Login();
login.setEmail(email);
login.setPassword(password);
ResponseData responseData = ResponseData.ok();
//先到数据库验证
Integer loginId = userService.checkLogin(login);
if(null != loginId) {
User user = userService.getUserByLoginId(loginId);
login.setId(loginId);
//给用户jwt加密生成token
String token = JWT.sign(login, 60L* 1000L* 30L);
//封装成对象返回给客户端
responseData.putDataValue("loginId", login.getId());
responseData.putDataValue("token", token);
responseData.putDataValue("user", user);
}
else{
responseData = ResponseData.customerError();
}
return responseData;
}
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>
<!-- 匹配的是url路径， 如果不配置或/**,将拦截所有的Controller -->
<mvc:mapping path="/**" />
<!-- /register 和 /login 不需要拦截-->
<mvc:exclude-mapping path="/register" />
<mvc:exclude-mapping path="/login" />
<bean class="com.xforce.charles.interceptor.TokenInterceptor"></bean>
</mvc:interceptor>
<!-- 当设置多个拦截器时，先按顺序调用preHandle方法，然后逆序调用每个拦截器的postHandle和afterCompletion方法 -->
</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 {
}
//拦截每个请求
public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
Object handler) throws Exception {
response.setCharacterEncoding("utf-8");
String token = request.getParameter("token");
ResponseData responseData = ResponseData.ok();
//token不存在
if(null != token) {
Login login = JWT.unsign(token, Login.class);
String loginId = request.getParameter("loginId");
//解密token后的loginId与用户传来的loginId不一致，一般都是token过期
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;
}
}
//请求不通过，返回错误信息给客户端
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();
}
}
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");
}
}