Symmetric AES encryption with Java

Crypto.java

package com.robbdimitrov.crypto;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Base64;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class Crypto {
    public static String generateKey() {
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(256);
            SecretKey secretKey = keyGenerator.generateKey();
            return Base64.getEncoder().encodeToString(secretKey.getEncoded());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String encrypt(String value, String secret) {
        SecretKey secretKey = decodeKey(secret);
        try {
            IvParameterSpec ivspec = generateIv();
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivspec);
            byte[] cipherText = cipher.doFinal(value.getBytes());
            byte[] data = concat(ivspec.getIV(), cipherText);
            return Base64.getEncoder().encodeToString(data);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String decrypt(String value, String secret) {
        SecretKey secretKey = decodeKey(secret);
        try {
            byte[] data = Base64.getDecoder().decode(value);
            IvParameterSpec ivspec = new IvParameterSpec(Arrays.copyOfRange(data, 0, 16));
            byte[] cipherText = Arrays.copyOfRange(data, 16, data.length);

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, secretKey, ivspec);
            byte[] plainText = cipher.doFinal(cipherText);
            return new String(plainText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    private static SecretKey decodeKey(String encodedKey) {
        byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
        return new SecretKeySpec(decodedKey, 0, decodedKey.length, "AES");
    }

    private static IvParameterSpec generateIv() {
        byte[] iv = new byte[16];
        new SecureRandom().nextBytes(iv);
        return new IvParameterSpec(iv);
    }

    private static byte[] concat(byte[] first, byte[] second) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        output.write(first);
        output.write(second);
        return output.toByteArray();
    }
}

CryptoTest.java

package com.robbdimitrov.crypto;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotEquals;
import static org.junit.Assert.assertNotNull;

import com.robbdimitrov.crypto.Crypto;

import org.junit.Test;

public class CryptoTest {
    @Test
    public void testGenerateKey() {
        String secret = Crypto.generateKey();
        assertNotNull(secret);
        assertNotEquals(secret.length(), 0);
        System.out.print("Secret = " + secret);
    }

    @Test
    public void testEncryption() {
        String secret = Crypto.generateKey();
        String plainText = "Text to be encrypted";

        String encrypted = Crypto.encrypt(plainText, secret);
        assertNotNull(encrypted);
        assertNotEquals(encrypted, plainText);

        String decrypted = Crypto.decrypt(encrypted, secret);
        assertEquals(decrypted, plainText);
    }
}