我利用 JWT 官網提供的 Java 模組，寫了個加密和解密token的例子。這個例子使用Maven管理專案，原始碼共包含三個檔案：Encrypt.java、Decrypt、Main.java

pom.xml

<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>zhangchao</groupId>
    <artifactId>testJavaJwt</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding
 
>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency
 
>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.1.0</version>
        </dependency>
    </dependencies>
</project>

Encrypt.java

package zhangchao;

import java.io.UnsupportedEncodingException;
import java.util.Date;

import com.auth0.jwt.JWT;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.exceptions.JWTCreationException;

/**
 * 加密
 * @author 張超
 *
 */
public final class Encrypt {

    /**
     * 生成加密後的token
     * @param isVip 是不是VIP,true表示是VIP，false表示不是VIP。
     * @param username 使用者名稱
     * @param name  姓名
     * @return 加密後的token
     */
    public String getToken(final boolean isVip, final String username,
            final String name) {
        String token = null;
        try {
            Date expiresAt = new Date(System.currentTimeMillis() + 24L * 60L * 3600L * 1000L);
            token = JWT.create()
                .withIssuer("auth0")
                .withClaim("isVip", isVip)
                .withClaim("username", username)
                .withClaim("name", name)
                .withExpiresAt(expiresAt)
                // 使用了HMAC256加密演算法。
                // mysecret是用來加密數字簽名的金鑰。
                .sign(Algorithm.HMAC256("mysecret"));
        } catch (JWTCreationException exception){
            //Invalid Signing configuration / Couldn't convert Claims.
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return token;
    }
}

Decrypt.java

package zhangchao;

import java.io.UnsupportedEncodingException;

import com.auth0.jwt.JWT;
import com.auth0.jwt.JWTVerifier;
import com.auth0.jwt.algorithms.Algorithm;
import com.auth0.jwt.exceptions.JWTVerificationException;
import com.auth0.jwt.interfaces.DecodedJWT;

/**
 * 解密
 * @author 張超
 *
 */
public final class Decrypt {

    /**
     * 先驗證token是否被偽造，然後解碼token。
     * @param token 字串token
     * @return 解密後的DecodedJWT物件，可以讀取token中的資料。
     */
    public DecodedJWT deToken(final String token) {
        DecodedJWT jwt = null;
        try {
            // 使用了HMAC256加密演算法。
            // mysecret是用來加密數字簽名的金鑰。
            JWTVerifier verifier = JWT.require(Algorithm.HMAC256("mysecret"))
                .withIssuer("auth0")
                .build(); //Reusable verifier instance
            jwt = verifier.verify(token);
        } catch (JWTVerificationException exception){
            //Invalid signature/claims
            exception.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return jwt;
    }
}

Main.java

package zhangchao;

import com.auth0.jwt.interfaces.DecodedJWT;

public class Main {

    public static void main(String[] args) {
        // 生成token
        Encrypt encrypt = new Encrypt();
        String token = encrypt.getToken(true, "zhangchao", "張超");

        // 列印token
        System.out.println("token: " + token);

        // 解密token
        Decrypt decrypt = new Decrypt();
        DecodedJWT jwt = decrypt.deToken(token);

        System.out.println("issuer: " + jwt.getIssuer());
        System.out.println("isVip:  " + jwt.getClaim("isVip").asBoolean());
        System.out.println("username: " + jwt.getClaim("username").asString());
        System.out.println("name:     " + jwt.getClaim("name").asString());
        System.out.println("過期時間：      " + jwt.getExpiresAt());

    }

}