首先需要匯入一個第三方jsr包，commons-codec.jar
下面是一個寫好的工具類，呼叫該類的方法，實現使用指定金鑰對明文進行加解密：

package util;

import java.io.UnsupportedEncodingException;
import java.util.Random;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;

public
 
 class AesUtil {

//byte陣列轉字串
    public static String byteToString(byte[] byte1)
            throws UnsupportedEncodingException {
        return new String(byte1);
    }
//加密時呼叫方法，三個引數分別是：明文，金鑰，向量，注意向量的長度只能是16byte，而且加密解密時必須使用一致的向量。
    public static byte[] AES_CBC_Encrypt(byte[] content, byte[] keyBytes,
            byte
 
[] iv) {

        try {
            SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(iv));
            byte[] result = cipher.doFinal(content);
            return
 
 result;
        } catch (Exception e) {
            System.out.println("exception:" + e.toString());
        }
        return null;
    }
//解密方法，三個引數：密文，金鑰，向量
    public static byte[] AES_CBC_Decrypt(byte[] content, byte[] keyBytes,
            byte[] iv) {

        try {
            SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
            byte[] result = cipher.doFinal(content);
            return result;
        } catch (Exception e) {
            // TODO Auto-generated catchblock
            System.out.println("exception:" + e.toString());
        }
        return null;
    }

    /**
     *將base64型別的字串轉成byte型別
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptBASE64(String key) throws Exception {
        return Base64.decodeBase64(key.getBytes());
    }

    /**
     * 將byte型別轉變為base64型別的字串
     * @param key
     * @return
     * @throws Exception
     */
    public static String encryptBASE64(byte[] key) throws Exception {
        return new String(Base64.encodeBase64(key));
    }
    /**
     * 這個方法在大多數時候是用不到的，可以選擇無視。
     * @param src byte陣列
     * @return 十六進位制的字串
     */
    public static String bytesToHexString(byte[] src) {
        StringBuilder stringBuilder = new StringBuilder();
        if (src == null || src.length <= 0) {
            return null;
        }
        for (int i = 0; i < src.length; i++) {
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if (hv.length() < 2) {
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }

    /**
     * 字串轉二進位制字串
     * 
     * @param str
     */

    public String toBinary(String str) {

        char[] strChar = str.toCharArray();
        String result = "";
        for (int i = 0; i < strChar.length; i++) {
            result += Integer.toBinaryString(strChar[i]) + "";
        }

        return result;
    }

    /**
     * 字串轉16進位制字串
     * @param s
     * @return
     */
    public static String strTo16(String s) {
        String str = "";
        for (int i = 0; i < s.length(); i++) {
            int ch = (int) s.charAt(i);
            String s4 = Integer.toHexString(ch);
            str = str + s4;
        }
        return str;
    }


    /**
     * 得到一個任意長度隨即金鑰
     * @param KeyLength
     * @return
     */
    public static String KeyCreate(int KeyLength) {

        String base = "ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678";
        Random random = new Random();
        StringBuffer Keysb = new StringBuffer();
        for (int i = 0; i < KeyLength; i++) // 生成指定位數的隨機祕鑰字串
        {
            int number = random.nextInt(base.length());
            Keysb.append(base.charAt(number));
        }
        return Keysb.toString();
    }
}

直接將上面的工具類複製到專案中，下面demo用來演示加密解密過程：

//明文
String returnMessageContent = "癥結所在";
//aes的key值
String key = AesUtil.KeyCreate(16);
//注意第一個引數-明文轉化為byte陣列的時候，一定要指定是按照utf-8的格式進行轉化的，不然對中文的加密就會出現加密後無法解密的情況。
//第三個引數-向量，一定是16byte長度的，這裡採用金鑰字串的前16位。
byte[] encrypted = AesUtil.AES_CBC_Encrypt(returnMessageContent.getBytes("utf-8"), key.getBytes(), key.substring(0, 16).getBytes());
//將加密後的密文轉成base64格式的字串
String secretWord = AesUtil.encryptBASE64(encrypted);

解密的demo

String chat_content = secretWord;
// 解密，獲得訊息明文
byte[] chat_contentming = AesUtil.AES_CBC_Decrypt(AesUtil.decryptBASE64(chat_content),aesming.getBytes(),aesming.substring(0, 16).getBytes());
//將明文byte按照utf-8的形式轉化為String字串
String messageming = new String(chat_contentming, "utf-8");