json web token(JWT)是一种新的用户认证方式,不同与以前的Session.
JWT不需要服务器端存储用户信息,当用户登录后,服务器将用户信息放入加密放入token,需要时再通过对token解密获取.

如下链接下载jjwt jar包导入项目：
http://mvnrepository.com/artifact/io.jsonwebtoken/jjwt

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import java.sql.Time;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;
import io.jsonwebtoken.Claims;
import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

public class JWTUtils {
    private static final String skey="SDKJSFZVCXZVDANGNGHJVC08-L";
       /**
         * 
         */
       public static SecretKey generalKey(){
            String stringKey = skey;
            byte[] encodedKey = Base64.decodeBase64(stringKey);
            SecretKey key = new SecretKeySpec(encodedKey, 0, encodedKey.length, "AES");
            return key;
        }
       /**
         * 
         */
        public static String createJWT(String id,String issuer, Map<String, Object> claims, long ttlMillis) throws Exception {
            SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
            
            long nowMillis = System.currentTimeMillis();
            Time now = new Time(nowMillis);
            System.out.println( " now :" + now);
            
            SecretKey key = generalKey();
            
            JwtBuilder builder = Jwts.builder()
                .setClaims(claims)
                .setId(id)
                .setIssuer(issuer)
                .setIssuedAt(now)
                .setSubject("1111")
                .signWith(signatureAlgorithm, key);
            System.out.println( " builder :" + builder);
            if (ttlMillis >= 0) {
                long expMillis = nowMillis + ttlMillis;
                System.out.println( " expMillis :" + expMillis);
                Time exp = new Time(expMillis);
                System.out.println( " exp :" + exp);
                builder.setExpiration(exp);
            }
            return builder.compact();
        }
           /**
             * 
             */
            public static String createJWT(String username, String pwd,long ttlMillis) throws Exception {
                SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
                
                Map<String, Object> claims = new HashMap<String, Object>();
                claims.put("userName", username);
                claims.put("pwd", pwd);
                
                long nowMillis = System.currentTimeMillis();
                Time now = new Time(nowMillis);
                System.out.println( " now :" + now);
                
                SecretKey key = generalKey();
                
                JwtBuilder builder = Jwts.builder()
                    .setClaims(claims)
                    .setIssuer(username)
                    .setIssuedAt(now)
                    .signWith(signatureAlgorithm, key);
                System.out.println( " builder :" + builder);
                if (ttlMillis >= 0) {
                    long expMillis = nowMillis + ttlMillis;
                    System.out.println( " expMillis :" + expMillis);
                    Time exp = new Time(expMillis);
                    System.out.println( " exp :" + exp);
                    builder.setExpiration(exp);
                }
                return builder.compact();
            }   
        /**
         *
         */
        public static Claims parseJWT(String jwt) throws Exception{
            SecretKey key = generalKey();
            Claims claims = Jwts.parser()         
               .setSigningKey(key)
               .parseClaimsJws(jwt)
               .getBody();
            System.out.println("ID: " + claims.getId());
            System.out.println("Subject: " + claims.getSubject());
            System.out.println("Issuer: " + claims.getIssuer());
            System.out.println("Expiration: " + claims.getExpiration());
            return claims;
        }
}
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