java 实现AES加密算法

下面是一个简单的 Java 实现 AES 加密算法的示例代码：

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class AESUtil {

    public static String encrypt(String plaintext, String key, String iv) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv.getBytes(StandardCharsets.UTF_8));
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] encrypted = cipher.doFinal(plaintext.getBytes());
        return Base64.getEncoder().encodeToString(encrypted);
    }

    public static String decrypt(String ciphertext, String key, String iv) throws Exception {
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "AES");
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv.getBytes(StandardCharsets.UTF_8));
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] decoded = Base64.getDecoder().decode(ciphertext);
        byte[] decrypted = cipher.doFinal(decoded);
        return new String(decrypted, StandardCharsets.UTF_8);
    }

    public static void main(String[] args) throws Exception {
        String plaintext = "Hello, world!";
        String key = "0123456789abcdef";
        String iv = "fedcba9876543210";

        String ciphertext = encrypt(plaintext, key, iv);
        System.out.println("Ciphertext: " + ciphertext);

        String decrypted = decrypt(ciphertext, key, iv);
        System.out.println("Decrypted: " + decrypted);
    }

}

注意：这只是一个简单的示例代码，实际使用中应该考虑更多的安全因素，比如密钥的生成和管理、IV 的随机性等。