java实现AES不调库

Java提供了javax.crypto包，可以用来实现AES加密算法。以下是一个简单的AES加密和解密示例代码：

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

public class AESUtil {

    public static String encrypt(String key, String plainText) throws Exception {
        byte[] raw = key.getBytes();
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(plainText.getBytes());
        return Base64.getEncoder().encodeToString(encrypted);
    }

    public static String decrypt(String key, String encryptedText) throws Exception {
        byte[] raw = key.getBytes();
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] encrypted = Base64.getDecoder().decode(encryptedText);
        byte[] original = cipher.doFinal(encrypted);
        return new String(original);
    }

    public static void main(String[] args) throws Exception {
        String key = "mysecretaeskey"; // AES密钥，长度为16或32字节
        String plainText = "Hello, world!"; // 待加密的明文

        String encryptedText = encrypt(key, plainText);
        System.out.println("Encrypted Text: " + encryptedText);

        String decryptedText = decrypt(key, encryptedText);
        System.out.println("Decrypted Text: " + decryptedText);
    }
}

以上代码使用AES算法和Base64编码实现了对明文的加密和解密。需要注意的是，AES密钥的长度必须为16或32字节，否则会抛出异常。