如何使用 autofac 实现多依赖注入装饰器

Question

我想用 IOC 容器 autofac 调用 MessageStore 类。

如何在最新版本的 autofac 中注册这个装饰器和复合模式？

这段代码结合了复合和装饰器模式，注意SOLID Principal。

我对此感到困惑。我的问题是，这段代码如何用 autofac 定义

var fileStore = new FileStore(new DirectoryInfo(HostingEnvironment.MapPath("~/file"))); var cacheStore = new CacheStore(fileStore, fileStore); var logStore = new LogStore(cacheStore, cacheStore); var messageStore = new MessageStore(logStore, logStore); messageStore.Save(12, "Hello");

public class FileStore :  IFileLocator, IStoreWriter,IStoreReader
{
    private readonly DirectoryInfo _workingDirectory;

    public FileStore(DirectoryInfo workDirectory)
    {
        if (workDirectory == null)
            throw new ArgumentNullException("workDirectory");

        if (!workDirectory.Exists)
            throw new ArgumentException("Directory not found", "workDirectory");

        _workingDirectory = workDirectory;
    }

    public virtual void Save(int id, string message)
    {
        var path = GetFileInfo(id).FullName;
        File.WriteAllText(path, message);
    }

    public virtual Maybe<string> Read(int id)
    {
        var file = GetFileInfo(id);

        if (!file.Exists)
            return new Maybe<string>();

        var path = file.FullName;
        return new Maybe<string>(File.ReadAllText(path));
    }

    public virtual FileInfo GetFileInfo(int id)
    {
        return new FileInfo(
            Path.Combine(_workingDirectory.FullName, id + ".txt"));
    }
}

public class CacheStore : IStoreWriter, IStoreReader
{
    private readonly ConcurrentDictionary<int, Maybe<string>> _cache;
    private readonly IStoreWriter _writer;
    private readonly IStoreReader _reader;

    public CacheStore(IStoreWriter writer, IStoreReader reader)
    {
        _cache = new ConcurrentDictionary<int, Maybe<string>>();
        _writer = writer;
        _reader = reader;
    }

    public virtual void Save(int id, string message)
    {
        _writer.Save(id, message);
        var m = new Maybe<string>(message);
        _cache.AddOrUpdate(id, m, (i, s) => m);
    }

    public virtual Maybe<string> Read(int id)
    {
        Maybe<string> retVal;
        if (_cache.TryGetValue(id, out retVal))
            return retVal;

        retVal = _reader.Read(id);
        if (retVal.Any())
            _cache.AddOrUpdate(id, retVal, (i, s) => retVal);
        return retVal;
    }
}

public class LogStore :  IStoreWriter, IStoreReader
{
    private readonly IStoreWriter _writer;
    private readonly IStoreReader _reader;
    public LogStore(IStoreWriter writer, IStoreReader reader)
    {
        _writer = writer;
        _reader = reader;
    }
    public void Save(int id, string message)
    {
        Log.Information("Saving message {id}.", id);
        _writer.Save(id, message);
        Log.Information("Saved message {id}.", id);
    }

    public Maybe<string> Read(int id)
    {
        Log.Debug("Reading message {id}.", id);
        var retVal = _reader.Read(id);
        if (retVal.Any())
            Log.Debug("Returning message {id}.", id);
        else
            Log.Debug("No message {id} found.", id);
        return retVal;
    }

}

 public class MessageStore
{
    private readonly IStoreWriter _writer;
    private readonly IStoreReader _reader;
    public MessageStore(IStoreWriter writer, IStoreReader reader)
    {
        if (writer == null)
            throw new ArgumentNullException("writer");
        if (reader == null)
            throw new ArgumentNullException("reader");
        _writer = writer;
        _reader = reader;
    }

    public void Save(int id, string message)
    {
        _writer.Save(id, message);
    }

    public Maybe<string> Read(int id)
    {
        return _reader.Read(id);
    }
}

Answer 1

鉴于您的所有商店都实现并使用IStoreReader 和IStoreWriter，您可以通过将它们组合成一个IStore 接口来简化事情。这可以是定义Save 和Read 方法的单个接口，也可以根据需要从现有的IStoreReader 和IStoreWriter 接口继承。

然后您可以将您的FileStore（这似乎是主要实现）注册为密钥服务。然后使用RegisterDecorator 注册缓存和日志装饰器。最后注册MessageStore，解析没有key的服务，就是最外层的装饰器。

builder.Register(f => new FileStore(new DirectoryInfo(HostingEnvironment.MapPath("~/file"))))
    .Keyed<IStore>("file");

builder.RegisterDecorator<IStore>(
    (c, inner) => new CacheStore(inner), fromKey: "file", toKey: "cache");

builder.RegisterDecorator<IStore>(
    (c, inner) => new LogStore(inner), fromKey: "cache", toKey: null);

builder.Register(c => new MessageStore(c.Resolve<IStore>()));

我确信围绕装饰器的 API 可以改进，这绝对是我打算很快做的事情。

Answer 2

谢谢亚历克斯。但我用下面的代码解决了，因为我不想创建IStore。你觉得我的讨论吗？

builder.Register(f => new FileStore(new DirectoryInfo(HostingEnvironment.MapPath("~/file")))) 
            .Named<IStoreWriter>("F-writer").Named<IStoreReader>("F-reader");
        builder.Register( 
            c => new CacheStore(c.ResolveNamed<IStoreWriter>("F-writer"), c.ResolveNamed<IStoreReader>("F-reader"))) 
            .Named<IStoreWriter>("C-writer").Named<IStoreReader>("C-reader"); 

        builder.Register( 
            c => new LogStore(c.ResolveNamed<IStoreWriter>("C-writer"), c.ResolveNamed<IStoreReader>("C-reader"))) 
            .Named<IStoreWriter>("L-writer").Named<IStoreReader>("L-reader"); 

        builder.Register( 
            c => 
                new MessageStore(c.ResolveNamed<IStoreWriter>("L-writer"), c.ResolveNamed<IStoreReader>("L-reader")));