java 微信工具类解密微信回调使用

public class WechatDecryptDataUtil {

public static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
    return new String(
            decryptOfDiyIV(
                    Base64.decode(encryptDataB64),
                    Base64.decode(sessionKeyB64),
                    Base64.decode(ivB64)
            )
    );
}

private static final String KEY_ALGORITHM = "AES";
private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
private static Key key;
private static Cipher cipher;

private static void init(byte[] keyBytes) {
    // 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 (keyBytes.length % base != 0) {
        int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
        byte[] temp = new byte[groups * base];
        Arrays.fill(temp, (byte) 0);
        System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
        keyBytes = temp;
    }
    // 初始化
    Security.addProvider(new BouncyCastleProvider());
    // 转化成JAVA的密钥格式
    key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
    try {
        // 初始化cipher
        cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
    } catch (Exception e) {
        e.printStackTrace();
    }
}

/**
 * 解密方法
 *
 * @param encryptedData 要解密的字符串
 * @param keyBytes      解密密钥
 * @param ivs           自定义对称解密算法初始向量 iv
 * @return 解密后的字节数组
 */
private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
    byte[] encryptedText = null;
    init(keyBytes);
    try {
        cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
        encryptedText = cipher.doFinal(encryptedData);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return encryptedText;
}

}