Exception in thread main java.lang.IllegalArgumentException secret key byte array cannot be null or empty

异常信息

Exception in thread "main" java.lang.IllegalArgumentException: secret key byte array cannot be null or empty.
	at io.jsonwebtoken.lang.Assert.notEmpty(Assert.java:204)
	at io.jsonwebtoken.impl.DefaultJwtBuilder.signWith(DefaultJwtBuilder.java:88)
	at io.jsonwebtoken.impl.DefaultJwtBuilder.signWith(DefaultJwtBuilder.java:100)
	at aa.main(aa.java:15)

异常原因

秘钥长度小于4位数

异常代码

public static void main(String[] args) {

	/* 生成jwt令牌 */
	JwtBuilder builder = Jwts.builder()
		.setId("123")
		.setSubject("123")
		.setIssuedAt(new Date())
		/* 秘钥长度必须大于3 */
		.signWith(SignatureAlgorithm.HS256,"123");

	System.out.println(builder.compact());
	
}