加密代码

        /**
         * 加密
         * 
         * @param content 需要加密的内容
         * @param password  加密密码
         * @return
         */
        public static byte[] encrypt(String content, String password) {
                try {           
                        KeyGenerator kgen = KeyGenerator.getInstance("AES");
                        kgen.init(128, new SecureRandom(password.getBytes()));
                        SecretKey secretKey = kgen.generateKey();
                        byte[] enCodeFormat = secretKey.getEncoded();
                        SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
                        Cipher cipher = Cipher.getInstance("AES");// 创建密码器
                        byte[] byteContent = content.getBytes("utf-8");
                        cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化
                        byte[] result = cipher.doFinal(byteContent);
                        return result; // 加密
                } catch (NoSuchAlgorithmException e) {
                        e.printStackTrace();
                } catch (NoSuchPaddingException e) {
                        e.printStackTrace();
                } catch (InvalidKeyException e) {
                        e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                        e.printStackTrace();
                } catch (IllegalBlockSizeException e) {
                        e.printStackTrace();
                } catch (BadPaddingException e) {
                        e.printStackTrace();
                }
                return null;
        }

解密代码

        /**解密
         * 解密的时候要传入byte数组
         * @param content  待解密内容
         * @param password 解密密钥
         * @return
         */
        public static byte[] decrypt(byte[] content, String password) {
                try {
                         KeyGenerator kgen = KeyGenerator.getInstance("AES");
                         kgen.init(128, new SecureRandom(password.getBytes()));
                         SecretKey secretKey = kgen.generateKey();
                         byte[] enCodeFormat = secretKey.getEncoded();
                         SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");            
                         Cipher cipher = Cipher.getInstance("AES");// 创建密码器
                        cipher.init(Cipher.DECRYPT_MODE, key);// 初始化
                        byte[] result = cipher.doFinal(content);
                        return result; // 加密
                } catch (NoSuchAlgorithmException e) {
                        e.printStackTrace();
                } catch (NoSuchPaddingException e) {
                        e.printStackTrace();
                } catch (InvalidKeyException e) {
                        e.printStackTrace();
                } catch (IllegalBlockSizeException e) {
                        e.printStackTrace();
                } catch (BadPaddingException e) {
                        e.printStackTrace();
                }
                return null;
        }

测试代码

           String content = "test";
           String password = "12345678";
           //加密
           System.out.println("加密前：" + content);
           byte[] encryptResult = encrypt(content, password);
           //解密
           byte[] decryptResult = decrypt(encryptResult,password);
           System.out.println("解密后：" + new String(decryptResult));

输出结果如下：
加密前：test
解密后：test

容易出错的地方：
如果我们将测试代码修改一下，如下：

           String content = "test";
           String password = "12345678";
           //加密
           System.out.println("加密前：" + content);
           byte[] encryptResult = encrypt(content, password);
           try {
                   String encryptResultStr = new String(encryptResult,"utf-8");
                   //解密
                   byte[] decryptResult = decrypt(encryptResultStr.getBytes("utf-8"),password);
                   System.out.println("解密后：" + new String(decryptResult));
           } catch (UnsupportedEncodingException e) {
                   e.printStackTrace();
           }

则，系统会报出如下异常：

javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
        at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
        at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
        at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)
        at javax.crypto.Cipher.doFinal(DashoA13*..)

这主要是因为加密后的byte数组是不能强制转换成字符串的，换言之：字符串和byte数组在这种情况下不是互逆的；要避免这种情况，我们需要做一些修订，可以考虑将二进制数据转换成十六进制表示，主要有如下两个方法：

二进制转换成16进制

        /**将二进制转换成16进制
         * @param buf
         * @return
         */
        public static String parseByte2HexStr(byte buf[]) {
                StringBuffer sb = new StringBuffer();
                for (int i = 0; i < buf.length; i++) {
                        String hex = Integer.toHexString(buf[i] & 0xFF);
                        if (hex.length() == 1) {
                                hex = '0' + hex;
                        }
                        sb.append(hex.toUpperCase());
                }
                return sb.toString();
        }

16进制转换为二进制

        /**将16进制转换为二进制
         * @param hexStr
         * @return
         */
        public static byte[] parseHexStr2Byte(String hexStr) {
                if (hexStr.length() < 1)
                        return null;
                byte[] result = new byte[hexStr.length()/2];
                for (int i = 0;i< hexStr.length()/2; i++) {
                        int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);
                        int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
                        result[i] = (byte) (high * 16 + low);
                }
                return result;
        }

然后，我们再修订以上测试代码，如下：

           String content = "test";
           String password = "12345678";
           //加密
           System.out.println("加密前：" + content);
           byte[] encryptResult = encrypt(content, password);
           String encryptResultStr = parseByte2HexStr(encryptResult);
           System.out.println("加密后：" + encryptResultStr);
           //解密
           byte[] decryptFrom = parseHexStr2Byte(encryptResultStr);
           byte[] decryptResult = decrypt(decryptFrom,password);
           System.out.println("解密后：" + new String(decryptResult));

测试结果如下：
加密前：test
加密后：73C58BAFE578C59366D8C995CD0B9D6D
解密后：test

另外一种加密方式

   /**
         * 加密
         *
         * @param content 需要加密的内容
         * @param password  加密密码
         * @return
         */
        public static byte[] encrypt2(String content, String password) {
                try {
                        SecretKeySpec key = new SecretKeySpec(password.getBytes(), "AES");
                        Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
                        byte[] byteContent = content.getBytes("utf-8");
                        cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化
                        byte[] result = cipher.doFinal(byteContent);
                        return result; // 加密
                } catch (NoSuchAlgorithmException e) {
                        e.printStackTrace();
                } catch (NoSuchPaddingException e) {
                        e.printStackTrace();
                } catch (InvalidKeyException e) {
                        e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                        e.printStackTrace();
                } catch (IllegalBlockSizeException e) {
                        e.printStackTrace();
                } catch (BadPaddingException e) {
                        e.printStackTrace();
                }
                return null;
        }

这种加密方式有两种限制
密钥必须是16位的
待加密内容的长度必须是16的倍数，如果不是16的倍数，就会出如下异常：

javax.crypto.IllegalBlockSizeException: Input length not multiple of 16 bytes
        at com.sun.crypto.provider.SunJCE_f.a(DashoA13*..)
        at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
        at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
        at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)
        at javax.crypto.Cipher.doFinal(DashoA13*..)

要解决如上异常，可以通过补全传入加密内容等方式进行避免。