使用JWT实现Token认证

为什么使用JWT？
随着技术的发展，分布式web应用的普及，通过session管理用户登录状态成本越来越高，因此慢慢发展成为token的方式做登录身份校验，然后通过token去取redis中的缓存的用户信息，随着之后jwt的出现，校验方式更加简单便捷化，无需通过redis缓存，而是直接根据token取出保存的用户信息，以及对token可用性校验，单点登录更为简单。

JWT架构图

JWT架构图.png

使用JWT核心代码：
maven依赖：

        <dependency>
            <groupId>com.auth0</groupId>
            <artifactId>java-jwt</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>io.jsonwebtoken</groupId>
            <artifactId>jjwt</artifactId>
            <version>0.7.0</version>
        </dependency>

JWT工具类：
用于生成Token，和Token验证

public class JwtUtils {
    /**
     * 签发JWT
     * @param id
     * @param subject 可以是JSON数据 尽可能少
     * @param ttlMillis
     * @return  String
     *
     */
    public static String createJWT(String id, String subject, long ttlMillis) {
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);
        SecretKey secretKey = generalKey();
        JwtBuilder builder = Jwts.builder()
                .setId(id)
                .setSubject(subject)   // 主题
                .setIssuer("user")     // 签发者
                .setIssuedAt(now)      // 签发时间
                .signWith(signatureAlgorithm, secretKey); // 签名算法以及密匙
        if (ttlMillis >= 0) {
            long expMillis = nowMillis + ttlMillis;
            Date expDate = new Date(expMillis);
            builder.setExpiration(expDate); // 过期时间
        }
        return builder.compact();
    }
    /**
     * 验证JWT
     * @param jwtStr
     * @return
     */
    public static CheckResult validateJWT(String jwtStr) {
        CheckResult checkResult = new CheckResult();
        Claims claims = null;
        try {
            claims = parseJWT(jwtStr);
            checkResult.setSuccess(true);
            checkResult.setClaims(claims);
        } catch (ExpiredJwtException e) {
            checkResult.setErrCode(SystemConstant.JWT_ERRCODE_EXPIRE);
            checkResult.setSuccess(false);
        } catch (SignatureException e) {
            checkResult.setErrCode(SystemConstant.JWT_ERRCODE_FAIL);
            checkResult.setSuccess(false);
        } catch (Exception e) {
            checkResult.setErrCode(SystemConstant.JWT_ERRCODE_FAIL);
            checkResult.setSuccess(false);
        }
        return checkResult;
    }
    public static SecretKey generalKey() {
        byte[] encodedKey = Base64.decode(SystemConstant.JWT_SECERT);
        SecretKey key = new SecretKeySpec(encodedKey, 0, encodedKey.length, "AES");
        return key;
    }
<span class="hljs-comment">/**
 * 
 * 解析JWT字符串
 * <span class="hljs-doctag">@param</span> jwt
 * <span class="hljs-doctag">@return</span>
 * <span class="hljs-doctag">@throws</span> Exception
 */</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> Claims <span class="hljs-title">parseJWT</span><span class="hljs-params">(String jwt)</span> <span class="hljs-keyword">throws</span> Exception </span>{
    SecretKey secretKey = generalKey();
    <span class="hljs-keyword">return</span> Jwts.parser()
        .setSigningKey(secretKey)
        .parseClaimsJws(jwt)
        .getBody();
}

}

如何使用？
代码实例：

public class LoginController {
    @Autowired
    UserRepository userRepository;
<span class="hljs-meta">@ApiOperation</span>(value=<span class="hljs-string">"用户登陆"</span>)
<span class="hljs-meta">@RequestMapping</span>(value=<span class="hljs-string">"login"</span>,method = RequestMethod.POST)
<span class="hljs-function"><span class="hljs-keyword">public</span> ReturnVo <span class="hljs-title">login</span><span class="hljs-params">(String username, String password,HttpServletResponse
        response)</span> </span>{
    User user =  userRepository.findByUsername(username);
    <span class="hljs-keyword">if</span>(user!=<span class="hljs-keyword">null</span>){
        <span class="hljs-keyword">if</span>(user.getPassword().equals(password)){
            <span class="hljs-comment">//把token返回给客户端--&gt;客户端保存至cookie--&gt;客户端每次请求附带cookie参数</span>
            String JWT = JwtUtils.createJWT(<span class="hljs-string">"1"</span>, username, SystemConstant.JWT_TTL);
            <span class="hljs-keyword">return</span> ReturnVo.ok(JWT);
        }<span class="hljs-keyword">else</span>{
            <span class="hljs-keyword">return</span> ReturnVo.error();
        }
    }<span class="hljs-keyword">else</span>{
        <span class="hljs-keyword">return</span> ReturnVo.error();
    }
}
<span class="hljs-meta">@ApiOperation</span>(value=<span class="hljs-string">"获取用户信息"</span>)
<span class="hljs-meta">@RequestMapping</span>(value=<span class="hljs-string">"description"</span>,method = RequestMethod.POST)
<span class="hljs-function"><span class="hljs-keyword">public</span> ReturnVo <span class="hljs-title">description</span><span class="hljs-params">(String username)</span> </span>{
    User user =  userRepository.findByUsername(username);
    <span class="hljs-keyword">return</span> ReturnVo.ok(user.getDescription());
}

}

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