Check out example codes for "java spring username encode and decode". It will help you in understanding the concepts better.

Code Example 1

private static final String ALGO = "AES";
private static final byte[] keyValue = new byte[] { 'T', 'E', 'S', 'T' };


/**
 * Encrypt a string using AES encryption algorithm.
 *
 * @param pwd the password to be encrypted
 * @return the encrypted string
 */
public static String encrypt(String pwd) {
    String encodedPwd = "";
    try {
        Key key = generateKey();
        Cipher c = Cipher.getInstance(ALGO);
        c.init(Cipher.ENCRYPT_MODE, key);
        byte[] encVal = c.doFinal(pwd.getBytes());
        encodedPwd = Base64.getEncoder().encodeToString(encVal);

    } catch (Exception e) {

        e.printStackTrace();
    }
    return encodedPwd;

}

/**
 * Decrypt a string with AES encryption algorithm.
 *
 * @param encryptedData the data to be decrypted
 * @return the decrypted string
 */
public static String decrypt(String encryptedData) {
    String decodedPWD = "";
    try {
        Key key = generateKey();
        Cipher c = Cipher.getInstance(ALGO);
        c.init(Cipher.DECRYPT_MODE, key);
        byte[] decordedValue = Base64.getDecoder().decode(encryptedData);
        byte[] decValue = c.doFinal(decordedValue);
        decodedPWD = new String(decValue);

    } catch (Exception e) {

    }
    return decodedPWD;
}

/**
 * Generate a new encryption key.
 */
private static Key generateKey() {
    SecretKeySpec key = new SecretKeySpec(keyValue, ALGO);
    return key;
}

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