15 minutes learn to use JWT

15 Learn to use in minutes JWT

brief introduction

What is? JWT?

JSON Web Token, By means of digital signature , With JSON The object is the carrier , Secure transmission of information between different service terminals .

JWT What's the usage? ？

JWT The most common scenario is authorization , Once the user logs in , Each subsequent request will contain JWT, Before each user request is processed by the system , You have to do it first JWT Security check , Process after passing .

JWT The composition of

JWT from 3 Part of it is made up of , use . Splicing

These are the three parts ：

Header

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

token type jwt encryption algorithm HS256

Payload

{
    
	'sub': '1234567890',
	'name': 'john',
    'admin': true
}

load Where valid information is stored A statement registered in the standard , Public statement , Private statement Conduct base64 Encryption gets the second part

Signature

var encodedString = base64UrlEncode(header) + '.' + base64UrlEncode(payload);

var signature = HMACSHA256(encodedString, 'secret');

Signature Add salt to encrypt to get the third part

rely on

pom.xml

<!-- Core dependence -->
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.9.1</version>
</dependency>


<!-- Use jwt, If it is jdk1.8 The above versions require these dependencies , Otherwise an error -->
<dependency>
    <groupId>javax.xml.bind</groupId>
    <artifactId>jaxb-api</artifactId>
    <version>2.3.0</version>
</dependency>

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.3.0</version>
</dependency>

<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-core</artifactId>
    <version>2.3.0</version>
</dependency>

<dependency>
    <groupId>javax.activation</groupId>
    <artifactId>activation</artifactId>
    <version>1.1.1</version>
</dependency>

encryption

Code example

@Test
public void testjwt() {
    
    // establish jwt object 
    JwtBuilder jwtBuilder = Jwts.builder();

    long time = 24*60*60*1000;

    // First define the signature information 
    String signature = "admin";

    //jwt  Three parts , The creation is also divided into three parts 
    String jwtToken = jwtBuilder
            //header
            .setHeaderParam("typ", "JWT")
            .setHeaderParam("alg","HS256")
            //payload  Loading 
            .claim("username", "tom")
            .claim("role", "admin")
            .setSubject("admin-test")    // Add theme 
            .setExpiration(new Date(System.currentTimeMillis()+time))      // Plus effective time here is one day 
            .setId(UUID.randomUUID().toString())
            //signature  Define algorithms and variables 
            .signWith(SignatureAlgorithm.HS256, signature)
            // The three parts should be put together 
            .compact();

    // Output 
    System.out.println(jwtToken);

}

Get the output jwtToken

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6InRvbSIsInJvbGUiOiJhZG1pbiIsInN1YiI6ImFkbWluLXRlc3QiLCJleHAiOjE2MzUyNTkyMTMsImp0aSI6IjFhMWYxYmZiLTJjOTMtNDNlMy1hMDVlLWJmZGZhNzJlYmIyZCJ9.7d1ciA2FcmUTHSk-Kkq2bbV3Z5LLGaXBGFQBAlvUnsg

Decrypt

@Test
public void parse () {
    String signature = "admin";
    String token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VybmFtZSI6InRvbSIsInJvbGUiOiJhZG1pbiIsInN1YiI6ImFkbWluLXRlc3QiLCJleHAiOjE2MzUyNTkyMTMsImp0aSI6IjFhMWYxYmZiLTJjOTMtNDNlMy1hMDVlLWJmZGZhNzJlYmIyZCJ9.7d1ciA2FcmUTHSk-Kkq2bbV3Z5LLGaXBGFQBAlvUnsg";
    JwtParser jwtParser = Jwts.parser();
    Jws<Claims> claimsJws = jwtParser.setSigningKey(signature).parseClaimsJws(token);
    Claims claims = claimsJws.getBody();   // What you get is a collection , Store all kinds of information in it 
    System.out.println(claims.get("username"));
    System.out.println(claims.get("role"));
    System.out.println(claims.getId());
    System.out.println(claims.getSubject());
    System.out.println(claims.getExpiration());


}

Get the output

tom
admin
1a1f1bfb-2c93-43e3-a05e-bfdfa72ebb2d
admin-test
Tue Oct 26 22:40:13 CST 2021