微信小程序登录解密encryptedData获取unionId，用户名，头像等信息

1 pom.xml文件添加依赖

        
            org.codehaus.xfire
            xfire-core
            1.2.6
        
        
            org.bouncycastle
            bcprov-jdk16
            1.46
        

2 解密encryptedData数据的方法

/**
     * 解密encryptedData获取用户信息
     *
     * @param encryptedData
     * @param sessionKey
     * @param iv
     * @return
     */
    public static JSONObject getUserInfo(String encryptedData, String sessionKey, String iv) {
        // 被加密的数据
        byte[] dataByte = Base64.decode(encryptedData);
        // 加密秘钥
        byte[] keyByte = Base64.decode(sessionKey);
        // 偏移量
        byte[] ivByte = Base64.decode(iv);

        try {
            // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
            int base = 16;
            if (keyByte.length % base != 0) {
                int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
                byte[] temp = new byte[groups * base];
                Arrays.fill(temp, (byte) 0);
                System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
                keyByte = temp;
            }
            // 初始化
            Security.addProvider(new BouncyCastleProvider());
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding", "BC");
            SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
            AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
            parameters.init(new IvParameterSpec(ivByte));
            cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化
            byte[] resultByte = cipher.doFinal(dataByte);
            if (null != resultByte && resultByte.length > 0) {
                String result = new String(resultByte, "UTF-8");
                return JSONObject.parseObject(result);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

备注：encryptedData和iv从小程序的getUserInfo接口获取

3 使用方法（伪代码）

Map userInfo = WXUtil.getUserInfo(encryptedData, sessionKey, iv);
String nickName = (String) userInfo.get("nickName"); //昵称
String avatarUrl = (String) userInfo.get("avatarUrl"); //头像
String unionId = (String) userInfo.get("unionId"); //unionid