裝飾者模式是一個很精美且優雅的模式
本篇範例 文字內容->AES加密->Zip檔附加密碼->輸出儲存
情境
有個需求要做
文字內容->壓縮zip(附上密碼)->輸出儲存
又改成...
文字內容->AES加密->輸出儲存
需求又改成....
文字內容->AES加密->Zip檔附加密碼->輸出儲存
可發現需求一直在對於文字內容操作順序做變化,但他們核心離不開對於文字內容的操作
這種情境很適合來使用 [裝飾者模式]
裝飾者模式 有兩個主要角色 被裝飾物件(Decorated) & 裝飾物件(Decorator)
一般先有蛋糕被裝飾物件(Decorated),後再將裝飾物品加上去裝飾物件(Decorator)
被裝飾物件(Decorated)如下圖 蛋糕的原型
第一步 先找尋他們共同裝飾東西,因為是讀寫檔案 所以我們可以對於Byte下手
先做出 讀 跟 寫 介面簽章當作裝飾動作的統一介面
石頭
public interface IProcess
{
byte[] Read(string path);
void Write(string writePath, byte[] buffer);
}
在創建一個 ProcessBase 給日後裝飾物品(Decorator)來繼承
public abstract class ProcessBase : IProcess
{
/// <summary>
/// 儲存被裝飾的物件
/// </summary>
protected IProcess _process;
public abstract byte[] Read(string path);
public abstract void Write(string writePath, byte[] buffer);
public virtual void SetDecorated(IProcess process)
{
_process = process;
}
}
有兩點特別說明
protected IProcess _process; 儲存被裝飾的物件由 SetDecorated 方法來設置被裝飾的物件第二步 創建被裝飾物品(Decorated)
因為是檔案我們直接使用
/// <summary>
/// 讀取檔案
/// </summary>
public class FileProcess : IProcess
{
public byte[] Read(string path)
{
return File.ReadAllBytes(path);
}
public void Write(string writePath, byte[] buffer)
{
File.WriteAllBytes(writePath, buffer);
}
}
第三步 創建裝飾物品(Decorator)
這次主要裝飾物品有兩個
加密裝飾器繼承ProcessBase並按照加解密重寫 Write和 read 方法
/// <summary>
/// Aes 加密裝飾器
/// </summary>
public class AESCrypProcess : ProcessBase
{
private AesCryptoServiceProvider aes;
public string AESKey { get; set; } = "1776D8E110124E75";
public string AESIV { get; set; } = "B890E7F6BA01C273";
public AESCrypProcess()
{
aes = new AesCryptoServiceProvider();
aes.Key = Encoding.UTF8.GetBytes(AESKey);
aes.IV = Encoding.UTF8.GetBytes(AESIV);
}
public override byte[] Read(string path)
{
byte[] encryptBytes = _process.Read(path);
return DecryptData(encryptBytes);
}
/// <summary>
/// 進行解密
/// </summary>
/// <param name="encryptBytes"></param>
/// <returns></returns>
private byte[] DecryptData(byte[] encryptBytes)
{
byte[] outputBytes = null;
using (MemoryStream memoryStream = new MemoryStream(encryptBytes))
{
using (CryptoStream decryptStream = new CryptoStream(memoryStream, aes.CreateDecryptor(), CryptoStreamMode.Read))
{
MemoryStream outputStream = new MemoryStream();
decryptStream.CopyTo(outputStream);
outputBytes = outputStream.ToArray();
}
}
return outputBytes;
}
/// <summary>
/// 裝飾者呼叫方法
/// </summary>
/// <param name="path"></param>
/// <param name="data"></param>
public override void Write(string path, byte[] data)
{
byte[] outputBytes = EncryptData(data);
_process.Write(path, outputBytes);
}
private byte[] EncryptData(byte[] data)
{
byte[] outputBytes = null;
using (MemoryStream memoryStream = new MemoryStream())
{
using (CryptoStream encryptStream = new CryptoStream(memoryStream, aes.CreateEncryptor(), CryptoStreamMode.Write))
{
MemoryStream inputStream = new MemoryStream(data);
inputStream.CopyTo(encryptStream);
encryptStream.FlushFinalBlock();
outputBytes = memoryStream.ToArray();
}
}
return outputBytes;
}
}
這次讀寫zip使用 SharpZipLib 開源第三方插件
ZIP裝飾器繼承ProcessBase並按照加解密重寫 Write和 read 方法
/// <summary>
/// 讀取Zip使用
/// </summary>
public class ZipProcess : ProcessBase
{
public string PassWord { get; set; }
public string FileName { get; set; }
public override byte[] Read(string path)
{
byte[] buffer = _process.Read(path);
return ZipReader(path, buffer);
}
public override void Write(string writePath, byte[] data)
{
byte[] buffer = ZipWriter(data);
_process.Write(writePath, buffer);
}
private byte[] ZipWriter(byte[] buffer)
{
using (MemoryStream outputMemStream = new MemoryStream())
using (ZipOutputStream zipStream = new ZipOutputStream(outputMemStream))
using (MemoryStream memStreamIn = new MemoryStream(buffer))
{
zipStream.SetLevel(9);
ZipEntry newEntry = new ZipEntry(FileName);
newEntry.DateTime = DateTime.Now;
zipStream.Password = PassWord;
zipStream.PutNextEntry(newEntry);
StreamUtils.Copy(memStreamIn, zipStream, new byte[4096]);//將zip流搬到memoryStream中
zipStream.CloseEntry();
zipStream.IsStreamOwner = false;
zipStream.Close();
return outputMemStream.ToArray();
}
}
/// <summary>
/// 讀取zip檔
/// </summary>
/// <param name="buffer">zip檔案byte</param>
/// <returns></returns>
private byte[] ZipReader(string filePath, byte[] buffer)
{
byte[] zipBuffer = default(byte[]);
using (MemoryStream memoryStream = new MemoryStream(buffer))
{
memoryStream.Seek(0, SeekOrigin.Begin);
var zip = new ZipFile(memoryStream);
zip.Password = PassWord;
using (MemoryStream streamWriter = new MemoryStream())
{
byte[] bufferReader = new byte[4096];
var file = zip.GetEntry(FileName); //設置要去得的檔名
//如果有檔案
if (file != null)
{
var zipStream = zip.GetInputStream(file);
StreamUtils.Copy(zipStream, streamWriter, bufferReader);
zipBuffer = streamWriter.ToArray();
}
}
}
return zipBuffer;
}
}
上面就把我們要用的裝飾物品 (備料) 準備完成
第四步 創建使用(開始擺盤)
創建一個 DecorateFactory 來當生產 裝飾產品的工廠
建構子傳入一個 被裝飾的物件(FileProcess) 之後可依照喜好一直疊加 裝飾物品(ZipProcess,AESCrypProcess...)
public class DecorateFactory
{
IProcess _original;
public DecorateFactory(IProcess original)
{
_original = original;
}
public DecorateFactory SetProcess(ProcessBase process)
{
process.SetDecorated(_original);
_original = process;
return this;
}
public IProcess GetProcess()
{
return _original;
}
}
裝飾者模式 裝飾的順序是很重要的
為了方便讀者閱讀 我使用小畫家畫出 讀寫順序
如下圖
使用就可很清晰來用
DecorateFactory來創建裝飾流程factroy.GetProcess(); 方法取得完成後的產品
在簡單呼叫讀和寫方法
string filePath = @"C:\Users\daniel.shih\Desktop\test.zip";
string content = $"你好 123456 12@()!@ {Environment.NewLine} fsfd嘻嘻哈哈!!";
//設置初始化的被裝飾者
DecorateFactory factroy = new DecorateFactory(new FileProcess());
//設置裝飾的順序
factroy.SetProcess(new AESCrypProcess())
.SetProcess(new ZipProcess() { FileName = "1.txt",PassWord ="1234567"});
IProcess process = factroy.GetProcess();
byte[] data_buffer = Encoding.UTF8.GetBytes(content);
process.Write(filePath, data_buffer);
byte[] buffer = process.Read(filePath);
Console.WriteLine(Encoding.UTF8.GetString(buffer));
日後不管需求是改成
還是.....
我們都不怕因為我們把各種操作封裝和多態
各個模組間都是獨立的很好映證 高內聚低耦合 的設計原則
小結:
裝飾者模式是一個很精美且優雅的模式 希望這篇文章可讓讀者對於此模式有更加了解
本文同步發佈 : https://dotblogs.com.tw/daniel/2018/04/09/102242
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