The specified key byte array is 136 bits which is not secure enough for any JWT HMAC-SHA algorithm.

场景

集合了<jjwt.version>0.11.5</jjwt.version>版本的 jwt

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

原 signWith 方法过时，更改后报错如下

主要错误信息如下

The specified key byte array is 136 bits which is not secure enough for any JWT HMAC-SHA algorithm.

2022-05-11 16:44:38.748 ERROR 83332 --- [io-13921-exec-1] o.a.c.c.C.[.[.[.[dispatcherServlet]      : Servlet.service() for servlet [dispatcherServlet] in context with path [/admin] threw exception [Request processing failed; nested exception is io.jsonwebtoken.security.WeakKeyException: The specified key byte array is 136 bits which is not secure enough for any JWT HMAC-SHA algorithm.  The JWT JWA Specification (RFC 7518, Section 3.2) states that keys used with HMAC-SHA algorithms MUST have a size >= 256 bits (the key size must be greater than or equal to the hash output size).  Consider using the io.jsonwebtoken.security.Keys#secretKeyFor(SignatureAlgorithm) method to create a key guaranteed to be secure enough for your preferred HMAC-SHA algorithm.  See https://tools.ietf.org/html/rfc7518#section-3.2 for more information.] with root cause

io.jsonwebtoken.security.WeakKeyException: The specified key byte array is 136 bits which is not secure enough for any JWT HMAC-SHA algorithm.  The JWT JWA Specification (RFC 7518, Section 3.2) states that keys used with HMAC-SHA algorithms MUST have a size >= 256 bits (the key size must be greater than or equal to the hash output size).  Consider using the io.jsonwebtoken.security.Keys#secretKeyFor(SignatureAlgorithm) method to create a key guaranteed to be secure enough for your preferred HMAC-SHA algorithm.  See https://tools.ietf.org/html/rfc7518#section-3.2 for more information.
	at io.jsonwebtoken.security.Keys.hmacShaKeyFor(Keys.java:96) ~[jjwt-api-0.11.5.jar:0.11.5]
	at com.admin.utils.JwtTokenUtils.generateToken(JwtTokenUtils.java:42) ~[classes/:na]
	at com.admin.service.AdminUserService.adminLogin(AdminUserService.java:59) ~[classes/:na]
	at com.admin.service.AdminUserService$$FastClassBySpringCGLIB$$1.invoke(<generated>) ~[classes/:na]
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.19.jar:5.3.19]
	at org.springframework.aop.framework.CglibAopProxy.invokeMethod(CglibAopProxy.java:386) ~[spring-aop-5.3.19.jar:5.3.19]
	at org.springframework.aop.framework.CglibAopProxy.access$000(CglibAopProxy.java:85) ~[spring-aop-5.3.19.jar:5.3.19]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:704) ~[spring-aop-5.3.19.jar:5.3.19]
	at com.admin.service.AdminUserService$$EnhancerBySpringCGLIB$$1.adminLogin(<generated>) ~[classes/:na]
	at com.admin.controller.UserController.adminLogin(UserController.java:26) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_332]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_332]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_332]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_332]

解决

给下述代码中的JWT_SECRET字段弄长点，大概 256 来个字符的时候就可以了

    /**
     * 根据用户信息生成token
     */
    public String generateToken(String username) {
    
    

        Claims claims = Jwts.claims().setSubject(username);

        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        SecretKey key = Keys.hmacShaKeyFor(JWT_SECRET.getBytes(StandardCharsets.UTF_8));
        return Jwts.builder()
                .setClaims(claims)
                .setExpiration(generateExpirationDate())
                .signWith(key, signatureAlgorithm)
                .compact();
    }