下面我们用springmvc和jwt的类库来实现一个例子。

要使用jwt，需要pom.xml中添加如下依赖

        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.2.0</version>
        </dependency>复制

下面贴一个完整的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.jstudioframework</groupId>
    <artifactId>jstudio-jwt</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <!-- 设置编码字符集 -->
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <!-- 集中定义依赖版本号 -->
        <junit.version>4.12</junit.version>
        <spring.version>4.3.7.RELEASE</spring.version>
        <jackson.version>2.8.4</jackson.version>
        <java.jwt.version>3.2.0</java.jwt.version>
        <jstl.version>1.2</jstl.version>
        <servlet-api.version>2.5</servlet-api.version>
        <jsp-api.version>2.2</jsp-api.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>${java.jwt.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- JSP相关 -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>${jstl.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>${servlet-api.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>${jsp-api.version}</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <!-- 配置插件 -->
        <plugins>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <configuration>
                    <port>8080</port>
                    <path>/</path>
                    <url>http://127.0.0.1:8080/manager/text</url>
                    <username>tomcat</username>
                    <password>tomcat</password>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>复制

一。定义一个jwt的工具类，具有加密和解密token的功能

import java.util.HashMap;
import java.util.Map;

/**
 * JwtToken
 */
public class JwtToken {

    //密钥
    private static final String SECRET = "secret";

    //jackson
    private static ObjectMapper mapper = new ObjectMapper();

    /**
     * header数据
     * @return
     */
    private static Map<String, Object> createHead() {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("typ", "JWT");
        map.put("alg", "HS256");
        return map;
    }

    /**
     * 生成token
     *
     * @param obj    对象数据
     * @param maxAge 有效期
     * @param <T>
     * @return
     */
    public static <T> String sign(T obj, long maxAge) throws UnsupportedEncodingException, JsonProcessingException {
        JWTCreator.Builder builder = JWT.create();

        builder.withHeader(createHead())//header
                .withSubject(mapper.writeValueAsString(obj));  //payload

        if (maxAge >= 0) {
            long expMillis = System.currentTimeMillis() + maxAge;
            Date exp = new Date(expMillis);
            builder.withExpiresAt(exp);
        }

        return builder.sign(Algorithm.HMAC256(SECRET));
    }

    /**
     * 解密
     * @param token   token字符串
     * @param classT  解密后的类型
     * @param <T>
     * @return
     */
    public static <T> T unsign(String token, Class<T> classT) throws IOException {
        JWTVerifier verifier = JWT.require(Algorithm.HMAC256(SECRET)).build();
        DecodedJWT jwt = verifier.verify(token);

        Date exp = jwt.getExpiresAt();
        if(exp!=null&&exp.after(new Date())){
            String subject = jwt.getSubject();
            return mapper.readValue(subject, classT);
        }

        return null;
    }

}
复制

二。 登录时根据用户传来的username和password验证身份，如果合法，便给该用户jwt加密生成token

package jwt.controller;

import com.fasterxml.jackson.core.JsonProcessingException;
import jwt.JwtToken;
import jwt.model.User;
import jwt.util.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.http.HttpServletRequest;
import java.io.UnsupportedEncodingException;

/**
 * 用户登录
 */

@Controller
public class LoginController {

    @RequestMapping(value="login", produces = "application/json; charset=utf-8")
    @ResponseBody
    public ResponseEntity login(HttpServletRequest request, @RequestParam( "username") String username,
                                @RequestParam("password") String password) throws UnsupportedEncodingException, JsonProcessingException {
        ResponseEntity responseEntity = ResponseEntity.ok();

        if("admin".equals(username) && "admin".equals(password)) {
            //模拟用户数据，真实环境需要到数据库验证
            User user = new User();
            user.setId(123456);
            user.setUsername(username);
            //给用户jwt加密生成token
            String token = JwtToken.sign(user, 60L * 1000L * 30L);
            //封装成对象返回给客户端
            responseEntity.putDataValue("userId", user.getId());
            responseEntity.putDataValue("token", token);
            responseEntity.putDataValue("user", user);
        }
        else{
            responseEntity =  ResponseEntity.customerError();
        }
        return responseEntity;
    }

}复制

User用户类如下

package jwt.model;

/**
 * User bean
 */
public class User {
    private long id;
    private String username;
    private String password;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}
复制

返回给用户端的一个工具类

package jwt.util;

import java.util.HashMap;
import java.util.Map;

public class ResponseEntity {

    public static final String ERRORS_KEY = "errors";

    private final String message;
    private final int code;
    private final Map<String, Object> data = new HashMap();

    public String getMessage() {
        return message;
    }

    public int getCode() {
        return code;
    }

    public Map<String, Object> getData() {
        return data;
    }

    public ResponseEntity putDataValue(String key, Object value) {
        data.put(key, value);
        return this;
    }

    private ResponseEntity(int code, String message) {
        this.code = code;
        this.message = message;
    }

    public static ResponseEntity ok() {
        return new ResponseEntity(200, "Ok");
    }

    public static ResponseEntity notFound() {
        return new ResponseEntity(404, "Not Found");
    }

    public static ResponseEntity badRequest() {
        return new ResponseEntity(400, "Bad Request");
    }

    public static ResponseEntity forbidden() {
        return new ResponseEntity(403, "Forbidden");
    }

    public static ResponseEntity unauthorized() {
        return new ResponseEntity(401, "unauthorized");
    }

    public static ResponseEntity serverInternalError() {
        return new ResponseEntity(500, "Server Internal Error");
    }

    public static ResponseEntity customerError() {
        return new ResponseEntity(1001, "Customer Error");
    }
}
复制

三。在用户登录后获得userId和token，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userId，与用户传递过来的userId比较，如果相同，则说明用户身份合法。这里用springmvc的拦截器实现验证。

注意:测试使用Params传递参数的，建议正式环境在header里添加参数

package jwt.interceptor;

import com.fasterxml.jackson.databind.ObjectMapper;
import jwt.JwtToken;
import jwt.model.User;
import jwt.util.ResponseEntity;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;

/**
 * Token验证拦截器
 */
public class UserTokenInterceptor implements HandlerInterceptor {

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object o) throws Exception {
        String token = request.getParameter("token");
        ResponseEntity responseData = ResponseEntity.ok();
        //token不存在
        if (token != null) {
            User user = JwtToken.unsign(token, User.class);
            String userId = request.getParameter("userId");
            //解密token后的userId与用户传来的userId不一致，大多是因为token过期
            if (user != null && userId != null && Integer.parseInt(userId) == user.getId()) {
                return true;
            }
        }

        responseData = ResponseEntity.forbidden();
        response.setContentType("application/json; charset=utf-8");
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(responseData);
        PrintWriter out = response.getWriter();
        out.print(json);
        out.flush();
        out.close();
        return false;
    }

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

    }
}
复制

四。springmvc的配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="jwt.controller"/>

    <mvc:annotation-driven />

    <!-- 拦截器设置 -->
    <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="jwt.interceptor.UserTokenInterceptor"></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>

    <!-- 默认的视图解析器 在上边的解析错误时使用 (默认使用html)- -->
    <bean id="defaultViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
        <property name="contentType" value="text/html"/>
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
        <property name="order" value="1"/>
    </bean>

</beans>复制

五。 使用Chrome插件Postman进行简单的测试

1.登录，http://localhost:8080/login

、

记下 token和userId

2. 测试token鉴权  http://localhost:8080/info

输入正确的userId和token

注意:测试使用Params传递参数的，建议正式环境在header里添加参数

输入错误的userId或token，在拦截器那里就被拦截了