Base64.encodeBase64String(secretKey.getEncoded())是apache的commons-codec庫，二進位制經base64編碼為字串

//cfb
package com.dddd.codec;

import org.apache.commons.codec.binary.Base64;

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

public class Test {

    public static void main(String[] args) {
        try {
            KeyGenerator kg= KeyGenerator.getInstance("AES");
            //初始化金鑰生成器，AES要求金鑰長度為128位、192位、256位
            kg.init(128);
            SecretKey secretKey=kg.generateKey();
            System.out.println("金鑰："+ Base64.encodeBase64String(secretKey.getEncoded()));

            SecretKey key=new SecretKeySpec(secretKey.getEncoded(),"AES");

            String txt = "testtxt";

            Cipher cipher= Cipher.getInstance("AES/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[]  encryptData = cipher.doFinal(txt.getBytes());
            System.out.println("加密後："+Base64.encodeBase64String(encryptData));

            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[]  decryptData = cipher.doFinal(encryptData);
            System.out.println("解密後："+new String(decryptData));


        }catch (Exception e){
            e.printStackTrace();
        }

    }
}
 

//gcm
package com.dddd.codec;

import org.apache.commons.codec.binary.Base64;

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

public class Test {

    public static void main(String[] args) {
        try {
            KeyGenerator kg= KeyGenerator.getInstance("AES");
            //初始化金鑰生成器，AES要求金鑰長度為128位、192位、256位
            kg.init(128);
            SecretKey secretKey=kg.generateKey();
            System.out.println("金鑰："+ Base64.encodeBase64String(secretKey.getEncoded()));

            SecretKey key=new SecretKeySpec(secretKey.getEncoded(),"AES");

            String txt = "testtxt";

            Cipher cipher= Cipher.getInstance("AES/GCM/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] iv = cipher.getIV(); 
            assert iv.length == 12;
            byte[]  encryptData = cipher.doFinal(txt.getBytes());
            assert encryptData.length == txt.getBytes().length + 16; 
            byte[] message = new byte[12 + txt.getBytes().length + 16]; 
            System.arraycopy(iv, 0, message, 0, 12);
            System.arraycopy(encryptData, 0, message, 12, encryptData.length);
            System.out.println("加密後："+Base64.encodeBase64String(message));


            if (message.length < 12 + 16) throw new IllegalArgumentException();
            GCMParameterSpec params = new GCMParameterSpec(128, message, 0, 12);
            cipher.init(Cipher.DECRYPT_MODE, key, params);
            byte[]  decryptData = cipher.doFinal(message, 12, message.length - 12);
            System.out.println("解密後："+new String(decryptData));


        }catch (Exception e){
            e.printStackTrace();
        }

    }
}