c# - XML 存储库实现

Question

我正在寻找一个简单的 Xml 存储库(GetAll、添加、更新、删除)示例。

每个人都说“使用存储库模式是个好主意，因为您可以交换数据存储位置...”现在我需要将数据存储在 xml 文件中，但不知道如何实现 XML 存储库。我在整个谷歌上搜索过，但找不到它。

如果可能，请发送包含关系数据句柄的示例。就像您在 EF 上保存产品实体时，所有产品相关实体也会持久化一样。

Answer 1

2020 年更新:已经有很好的 nuget 包可以很好地处理这个问题，例如 SharpRepository.XmlRepository ，它是许多存储库实现套件的一部分。

---

嗯，Petter 解决方案很好。

只是为了分享我的实现，我会再次回答我的问题，我希望这对某人有用。请评价和评论。

public interface IRepository<T>
{
    IEnumerable<T> GetAll();
    IEnumerable<T> GetAll(object parentId);
    T GetByKey(object keyValue);

    void Insert(T entidade, bool autoPersist = true);
    void Update(T entidade, bool autoPersist = true);
    void Delete(T entidade, bool autoPersist = true);

    void Save();
}

以及 XML 存储库的基类

public abstract class XmlRepositoryBase<T> : IRepository<T>
{

    public virtual XElement ParentElement { get; protected set; }

    protected XName ElementName { get; private set; }

    protected abstract Func<XElement, T> Selector { get; }

    #endregion

    protected XmlRepositoryBase(XName elementName)
    {
        ElementName = elementName;

        // clears the "cached" ParentElement to allow hot file changes
        XDocumentProvider.Default.CurrentDocumentChanged += (sender, eventArgs) => ParentElement = null;
    }

    #region

    protected abstract void SetXElementValue(T model, XElement element);

    protected abstract XElement CreateXElement(T model);

    protected abstract object GetEntityId(T entidade);

    #region IRepository<T>

    public T GetByKey(object keyValue)
    {
        // I intend to remove this magic string "Id"
        return XDocumentProvider.Default.GetDocument().Descendants(ElementName)
            .Where(e => e.Attribute("Id").Value == keyValue.ToString())
            .Select(Selector)
            .FirstOrDefault();
    }

    public IEnumerable<T> GetAll()
    {
        return ParentElement.Elements(ElementName).Select(Selector);
    }

    public virtual IEnumerable<T> GetAll(object parentId)
    {
        throw new InvalidOperationException("This entity doesn't contains a parent.");
    }

    public virtual void Insert(T entity, bool autoPersist = true)
    {
        ParentElement.Add(CreateXElement(entity));

        if (autoPersist)
            Save();
    }

    public virtual void Update(T entity, bool autoPersist= true)
    {
        // I intend to remove this magic string "Id"
        SetXElementValue(
            entity,
            ParentElement.Elements().FirstOrDefault(a => a.Attribute("Id").Value == GetEntityId(entity).ToString()
        ));

        if (persistir)
            Save();
    }

    public virtual void Delete(T entity, bool autoPersist = true)
    {
        ParentElement.Elements().FirstOrDefault(a => a.Attribute("Id").Value == GetEntityId(entity).ToString()).Remove();

        if (autoPersist)
            Save();
    }


    public virtual void Save()
    {
        XDocumentProvider.Default.Save();
    }
    #endregion

    #endregion
}

还有 2 个抽象类，一个用于独立实体，另一个用于子实体。为了避免每次都读取xml文件，我做了一种缓存控制

public abstract class EntityXmlRepository<T> : XmlRepositoryBase<T>
{
    #region cache control

    private XElement _parentElement;
    private XName xName;

    protected EntityXmlRepository(XName entityName)
        : base(entityName)
    {
    }

    public override XElement ParentElement
    {
        get
        {
            // returns in memory element or get it from file
            return _parentElement ?? ( _parentElement = GetParentElement() );
        }
        protected set
        {
            _parentElement = value;
        }
    }

    /// <summary>
    /// Gets the parent element for this node type
    /// </summary>
    protected abstract XElement GetParentElement();
    #endregion
}

现在是子类型的实现

public abstract class ChildEntityXmlRepository<T> : XmlRepositoryBase<T>
{
    private object _currentParentId;
    private object _lastParentId;

    private XElement _parentElement;

    public override XElement ParentElement
    {
        get 
        {
            if (_parentElement == null)
            {
                _parentElement = GetParentElement(_currentParentId);
                _lastParentId = _currentParentId;
            }
            return _parentElement;
        }
        protected set 
        {
            _parentElement = value; 
        }
    }

    /// <summary>
    /// Defines wich parent entity is active
    /// when this property changes, the parent element field is nuled, forcing the parent element to be updated
    /// </summary>
    protected object CurrentParentId
    {
        get
        {
            return _currentParentId;
        }
        set
        {
            _currentParentId = value;
            if (value != _lastParentId)
            {
                _parentElement = null;
            }
        }
    }       



    protected ChildEntityXmlRepository(XName entityName) : base(entityName){}

    protected abstract XElement GetParentElement(object parentId);

    protected abstract object GetParentId(T entity);


    public override IEnumerable<T> GetAll(object parentId)
    {
        CurrentParentId = parentId;
        return ParentElement.Elements(ElementName).Select(Selector);
    }

    public override void Insert(T entity, bool persistir = true)
    {
        CurrentParentId = GetParentId(entity);
        base.Insert(entity, persistir);
    }

    public override void Update(T entity, bool persistir = true)
    {
        CurrentParentId = GetParentId(entity);
        base.Update(entity, persistir);
    }

    public override void Delete(T entity, bool persistir = true)
    {
        CurrentParentId = GetParentId(entity);
        base.Delete(entity, persistir);
    }
}

现在，一个真实世界的实现

public class RepositorioAgendamento : EntityXmlRepository<Agendamento>, IRepositorioAgendamento
{
    protected override Func<XElement, Agendamento> Selector
    {
        get
        {
            return x => new Agendamento() {
                Id = x.Attribute("Id").GetGuid(),
                   Descricao = x.Attribute("Descricao").Value,
                   TipoAgendamento = x.Attribute("TipoAgendamento").GetByte(),
                   Dias = x.Attribute("Dias").GetByte(),
                   Data = x.Attribute("Data").GetDateTime(),
                   Ativo = x.Attribute("Ativo").GetBoolean(),
            };
        }
    }

    protected override XElement CreateXElement(Agendamento agendamento)
    {
        agendamento.Id = Guid.NewGuid();

        return new XElement(ElementName,
                new XAttribute("Id", agendamento.Id),
                new XAttribute("Descricao", agendamento.Descricao),
                new XAttribute("TipoAgendamento", agendamento.TipoAgendamento),
                new XAttribute("Dias", agendamento.Dias),
                new XAttribute("Data", agendamento.Data),
                new XAttribute("Ativo", agendamento.Ativo),
                new XElement(XmlNames.GruposBackup),
                new XElement(XmlNames.Credenciais)
                );
    }

    protected override void SetXElementValue(Agendamento modelo, XElement elemento)
    {
        elemento.Attribute("Descricao").SetValue(modelo.Descricao);
        elemento.Attribute("TipoAgendamento").SetValue(modelo.TipoAgendamento);
        elemento.Attribute("Dias").SetValue(modelo.Dias);
        elemento.Attribute("Data").SetValue(modelo.Data);
        elemento.Attribute("Ativo").SetValue(modelo.Ativo);
    }


    public RepositorioAgendamento() : base(XmlNames.Agendamento)
    {

    }

    protected override XElement GetParentElement()
    {
        return XDocumentProvider.Default.GetDocument().Elements(XmlNames.Agendamentos).First();
    }

    protected override object GetEntityId(Agendamento entidade)
    {
        return entidade.Id;
    }

    public IEnumerable<Agendamento> ObterAtivos()
    {
        return ParentElement.Elements()
            .Where(e => e.Attribute("Ativo").GetBoolean())
            .Select(Selector);
    }
}

现在，XDocumentProvider。它的作用是抽象出对xml文件的访问，统一到所有的repositories，什么XDocument是data context。 这可以命名为 UnitOfWork？

public abstract class XDocumentProvider
{
    // not thread safe yet
    private static bool pendingChanges;

    private bool _documentLoadedFromFile;

    FileSystemWatcher fileWatcher;

    public static XDocumentProvider Default;

    public event EventHandler CurrentDocumentChanged;

    private XDocument _loadedDocument;

    public string FileName { get; set; }


    protected XDocumentProvider()
    {
        fileWatcher = new FileSystemWatcher();
        fileWatcher.NotifyFilter = NotifyFilters.LastWrite;
        fileWatcher.Changed += fileWatcher_Changed;
    }

    void fileWatcher_Changed(object sender, FileSystemEventArgs e)
    {
        if (_documentLoadedFromFile && !pendingChanges)
        {
            GetDocument(true);
        }
    }


    /// <summary>
    /// Returns an open XDocument or create a new document
    /// </summary>
    /// <returns></returns>
    public XDocument GetDocument(bool refresh = false)
    {
        if (refresh || _loadedDocument == null)
        {
            // we need to refactor it, but just to demonstrate how should work I will send this way ;P
            if (File.Exists(FileName))
            {
                _loadedDocument = XDocument.Load(FileName);
                _documentLoadedFromFile = true;

                if (fileWatcher.Path != Environment.CurrentDirectory)
                {
                    fileWatcher.Path = Environment.CurrentDirectory;
                    fileWatcher.Filter = FileName;
                    fileWatcher.EnableRaisingEvents = true;
                }
            }
            else
            {
                _loadedDocument = CreateNewDocument();
                fileWatcher.EnableRaisingEvents = false;
                _documentLoadedFromFile = false;
            }

            if(CurrentDocumentChanged != null) CurrentDocumentChanged(this, EventArgs.Empty);
        }

        return _loadedDocument;
    }

    /// <summary>
    /// Creates a new XDocument with a determined schemma.
    /// </summary>
    public abstract XDocument CreateNewDocument();

    public void Save()
    {
        if (_loadedDocument == null)
            throw new InvalidOperationException();

        try
        {
            // tells the file watcher that he cannot raise the changed event, because his function is to capture external changes.
            pendingChanges = true;
            _loadedDocument.Save(FileName);
        }
        finally
        {
            pendingChanges = false;
        }
    }
}

然后我可以为不同的实体创建许多存储库，在单个数据上下文中添加挂起的持久性操作。

我已经使用模拟对使用此存储库的应用程序进行了测试并且运行良好。

在我的 IoC 配置中，我必须为 XDocumentProvider 设置默认值。如有必要，我们可以通过构造函数传递 XDocumentProvider 而不是这个静态“默认”属性

您如何看待我的实现？

谢谢