JWTString=Base64(Header).Base64(Payload).HMACSHA256(base64UrlEncode(header)+"."+base64UrlEncode(payload),secret)

{
  "alg": "HS256",
  "typ": "JWT"
}

iss：發(fā)行人
exp：到期時(shí)間
sub：主題
aud：用戶
nbf：在此之前不可用
iat：發(fā)布時(shí)間
jti：JWT ID用于標(biāo)識(shí)該JWT

{
  "sub": "1234567890",
  "name": "Helen",
  "admin": true
}

{
  "alg": "none",
  "typ": "JWT"
}

<dependency>
    <groupId>com.auth0</groupId>
    <artifactId>java-jwt</artifactId>
    <version>3.10.3</version>
</dependency>

public class JWTTest {
    @Test
    public void testGenerateToken(){
        // 指定token過期時(shí)間為10秒
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.SECOND, 10);

        String token = JWT.create()
                .withHeader(new HashMap<>())  // Header
                .withClaim("userId", 21)  // Payload
                .withClaim("userName", "baobao")
                .withExpiresAt(calendar.getTime())  // 過期時(shí)間
                .sign(Algorithm.HMAC256("!34ADAS"));  // 簽名用的secret

        System.out.println(token);
    }
}

@Test
public void testResolveToken(){
    // 創(chuàng)建解析對(duì)象，使用的算法和secret要與創(chuàng)建token時(shí)保持一致
    JWTVerifier jwtVerifier = JWT.require(Algorithm.HMAC256("!34ADAS")).build();
    // 解析指定的token
    DecodedJWT decodedJWT = jwtVerifier.verify("eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyTmFtZSI6ImJhb2JhbyIsImV4cCI6MTU5OTkyMjUyOCwidXNlcklkIjoyMX0.YhA3kh9KZOAb7om1C7o3vBhYp0f61mhQWWOoCrrhqvo");
    // 獲取解析后的token中的payload信息
    Claim userId = decodedJWT.getClaim("userId");
    Claim userName = decodedJWT.getClaim("userName");
    System.out.println(userId.asInt());
    System.out.println(userName.asString());
    // 輸出超時(shí)時(shí)間
    System.out.println(decodedJWT.getExpiresAt());
}

public class JWTUtils {
    // 簽名密鑰
    private static final String SECRET = "!DAR$";

    /**
     * 生成token
     * @param payload token攜帶的信息
     * @return token字符串
     */
    public static String getToken(Map<String,String> payload){
        // 指定token過期時(shí)間為7天
        Calendar calendar = Calendar.getInstance();
        calendar.add(Calendar.DATE, 7);

        JWTCreator.Builder builder = JWT.create();
        // 構(gòu)建payload
        payload.forEach((k,v) -> builder.withClaim(k,v));
        // 指定過期時(shí)間和簽名算法
        String token = builder.withExpiresAt(calendar.getTime()).sign(Algorithm.HMAC256(SECRET));
        return token;
    }
    /**
     * 解析token
     * @param token token字符串
     * @return 解析后的token
     */
    public static DecodedJWT decode(String token){
        JWTVerifier jwtVerifier = JWT.require(Algorithm.HMAC256(SECRET)).build();
        DecodedJWT decodedJWT = jwtVerifier.verify(token);
        return decodedJWT;
    }
}

private static final String RSA_PRIVATE_KEY = "...";
private static final String RSA_PUBLIC_KEY = "...";

/**
     * 生成token
     * @param payload token攜帶的信息
     * @return token字符串
     */
public static String getTokenRsa(Map<String,String> payload){
    // 指定token過期時(shí)間為7天
    Calendar calendar = Calendar.getInstance();
    calendar.add(Calendar.DATE, 7);

    JWTCreator.Builder builder = JWT.create();
    // 構(gòu)建payload
    payload.forEach((k,v) -> builder.withClaim(k,v));

    // 利用hutool創(chuàng)建RSA
    RSA rsa = new RSA(RSA_PRIVATE_KEY, null);
    // 獲取私鑰
    RSAPrivateKey privateKey = (RSAPrivateKey) rsa.getPrivateKey();
    // 簽名時(shí)傳入私鑰
    String token = builder.withExpiresAt(calendar.getTime()).sign(Algorithm.RSA256(null, privateKey));
    return token;
}

/**
     * 解析token
     * @param token token字符串
     * @return 解析后的token
     */
public static DecodedJWT decodeRsa(String token){
    // 利用hutool創(chuàng)建RSA
    RSA rsa = new RSA(null, RSA_PUBLIC_KEY);
    // 獲取RSA公鑰
    RSAPublicKey publicKey = (RSAPublicKey) rsa.getPublicKey();
    // 驗(yàn)簽時(shí)傳入公鑰
    JWTVerifier jwtVerifier = JWT.require(Algorithm.RSA256(publicKey, null)).build();
    DecodedJWT decodedJWT = jwtVerifier.verify(token);
    return decodedJWT;
}

<!-- https://mvnrepository.com/artifact/io.jsonwebtoken/jjwt -->
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>

public class JwtUtils {
    // token時(shí)效：24小時(shí)
    public static final long EXPIRE = 1000 * 60 * 60 * 24;
    // 簽名哈希的密鑰，對(duì)于不同的加密算法來說含義不同
    public static final String APP_SECRET = "ukc8BDbRigUDaY6pZFfWus2jZWLPHO";

    /**
     * 根據(jù)用戶id和昵稱生成token
     * @param id  用戶id
     * @param nickname 用戶昵稱
     * @return JWT規(guī)則生成的token
     */
    public static String getJwtToken(String id, String nickname){
        String JwtToken = Jwts.builder()
                .setHeaderParam("typ", "JWT")
                .setHeaderParam("alg", "HS256")
                .setSubject("baobao-user")
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + EXPIRE))
                .claim("id", id)
                .claim("nickname", nickname)
            	// HS256算法實(shí)際上就是MD5加鹽值，此時(shí)APP_SECRET就代表鹽值
                .signWith(SignatureAlgorithm.HS256, APP_SECRET)
                .compact();

        return JwtToken;
    }

    /**
     * 判斷token是否存在與有效
     * @param jwtToken token字符串
     * @return 如果token有效返回true，否則返回false
     */
    public static boolean checkToken(String jwtToken) {
        if(StringUtils.isEmpty(jwtToken)) return false;
        try {
            Jwts.parser().setSigningKey(APP_SECRET).parseClaimsJws(jwtToken);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    /**
     * 判斷token是否存在與有效
     * @param request Http請(qǐng)求對(duì)象
     * @return 如果token有效返回true，否則返回false
     */
    public static boolean checkToken(HttpServletRequest request) {
        try {
            // 從http請(qǐng)求頭中獲取token字符串
            String jwtToken = request.getHeader("token");
            if(StringUtils.isEmpty(jwtToken)) return false;
            Jwts.parser().setSigningKey(APP_SECRET).parseClaimsJws(jwtToken);
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }

    /**
     * 根據(jù)token獲取會(huì)員id
     * @param request Http請(qǐng)求對(duì)象
     * @return 解析token后獲得的用戶id
     */
    public static String getMemberIdByJwtToken(HttpServletRequest request) {
        String jwtToken = request.getHeader("token");
        if(StringUtils.isEmpty(jwtToken)) return "";
        Jws<Claims> claimsJws = Jwts.parser().setSigningKey(APP_SECRET).parseClaimsJws(jwtToken);
        Claims claims = claimsJws.getBody();
        return (String)claims.get("id");
    }
}

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-api</artifactId>
    <version>0.11.2</version>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-impl</artifactId>
    <version>0.11.2</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-jackson</artifactId> <!-- or jjwt-gson if Gson is preferred -->
    <version>0.11.2</version>
    <scope>runtime</scope>
</dependency>

public class JwtUtils {
    // token時(shí)效：24小時(shí)
    public static final long EXPIRE = 1000 * 60 * 60 * 24;
    // 簽名哈希的密鑰，對(duì)于不同的加密算法來說含義不同
    public static final String APP_SECRET = "ukc8BDbRigUDaY6pZFfWus2jZWLPHOsdadasdasfdssfeweee";

    /**
     * 根據(jù)用戶id和昵稱生成token
     * @param id  用戶id
     * @param nickname 用戶昵稱
     * @return JWT規(guī)則生成的token
     */
    public static String getJwtToken(String id, String nickname){
        String JwtToken = Jwts.builder()
                .setSubject("baobao-user")
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + EXPIRE))
                .claim("id", id)
                .claim("nickname", nickname)
                // 傳入Key對(duì)象
                .signWith(Keys.hmacShaKeyFor(APP_SECRET.getBytes(StandardCharsets.UTF_8)), SignatureAlgorithm.HS256)
                .compact();
        return JwtToken;
    }

    /**
     * 判斷token是否存在與有效
     * @param jwtToken token字符串
     * @return 如果token有效返回true，否則返回false
     */
    public static Jws<Claims> decode(String jwtToken) {
        // 傳入Key對(duì)象
        Jws<Claims> claimsJws = Jwts.parserBuilder().setSigningKey(Keys.hmacShaKeyFor(APP_SECRET.getBytes(StandardCharsets.UTF_8))).build().parseClaimsJws(jwtToken);
        return claimsJws;
    }
}

private static final String RSA_PRIVATE_KEY = "...";
private static final String RSA_PUBLIC_KEY = "...";

/**
     * 根據(jù)用戶id和昵稱生成token
     * @param id  用戶id
     * @param nickname 用戶昵稱
     * @return JWT規(guī)則生成的token
     */
public static String getJwtTokenRsa(String id, String nickname){
    // 利用hutool創(chuàng)建RSA
    RSA rsa = new RSA(RSA_PRIVATE_KEY, null);
    RSAPrivateKey privateKey = (RSAPrivateKey) rsa.getPrivateKey();
    String JwtToken = Jwts.builder()
        .setSubject("baobao-user")
        .setIssuedAt(new Date())
        .setExpiration(new Date(System.currentTimeMillis() + EXPIRE))
        .claim("id", id)
        .claim("nickname", nickname)
        // 簽名指定私鑰
        .signWith(privateKey, SignatureAlgorithm.RS256)
        .compact();
    return JwtToken;
}

/**
     * 判斷token是否存在與有效
     * @param jwtToken token字符串
     * @return 如果token有效返回true，否則返回false
     */
public static Jws<Claims> decodeRsa(String jwtToken) {
    RSA rsa = new RSA(null, RSA_PUBLIC_KEY);
    RSAPublicKey publicKey = (RSAPublicKey) rsa.getPublicKey();
    // 驗(yàn)簽指定公鑰
    Jws<Claims> claimsJws = Jwts.parserBuilder().setSigningKey(publicKey).build().parseClaimsJws(jwtToken);
    return claimsJws;
}

public class JWTInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String JWT = request.getHeader("Authorization");
        try {
            // 1.校驗(yàn)JWT字符串
            DecodedJWT decodedJWT = JWTUtils.decode(JWT);
            // 2.取出JWT字符串載荷中的隨機(jī)token，從Redis中獲取用戶信息
            ...
            return true;
        }catch (SignatureVerificationException e){
            System.out.println("無效簽名");
            e.printStackTrace();
        }catch (TokenExpiredException e){
            System.out.println("token已經(jīng)過期");
            e.printStackTrace();
        }catch (AlgorithmMismatchException e){
            System.out.println("算法不一致");
            e.printStackTrace();
        }catch (Exception e){
            System.out.println("token無效");
            e.printStackTrace();
        }
        return false;
    }
}