基于本地文件系统的LocalDB

时间：2017-05-18 11:42:50 阅读：371 评论：0 收藏：0 [点我收藏+]

标签：basedir region isnull public end direct search linq 比较

零、前言

　　之前写一些小工具的时候，需要用到数据存储方面的技术，但是用数据库又觉得太大了，本地文件存储txt文件存储又不是很规范，于是乎想到了去编写一个简单的基于本地文件系统的数据存储库，暂且叫它localdb吧，总之也是为了方便使用，特别是数据量不大，但是又特别想要本地数据存储的。（抛开access不说）

一、工具

　　工欲善其事必先利其器，存储数据必然要有一个标准的数据格式，首先让我想到的就是json,xml，原因不必多说。所以下面编写的数据主要以json作为存储格式。json操作用Newtonjson，操作方便简单。

二、文件系统的操作（LocalFileDB）

　　本地数据库，必不可少对本地文件进行操作，所以对本地文件的读取创建统一管理，话不多说，直接上代码。

　　首先添加自定义的异常：

    /// <summary>
    /// 文件数据库异常
    /// </summary>
    public class FileDatabaseException : Exception
    {
        public FileDatabaseException(string message)
            : base(message)
        { }

        public FileDatabaseException(string message, Exception innerException)
            : base(message, innerException)
        { }
    }

View Code

　　然后是具体操作文件的代码（这块有参考别人的，仅供学习使用，如有侵权，请联系我）：

    /// <summary>
    /// 文件数据库，这是一个抽象类。(之前做的拿来用的，也可以应用于xml,但已有linq to xml，所以这边暂时仅用于json)
    /// </summary>
    public abstract class FileDatabase<TEntity>
    {
        #region Fields

        /// <summary>
        /// 文件数据库操作锁
        /// </summary>
        protected static readonly object operationLock = new object();
        private static HashSet<char> invalidFileNameChars;

        static FileDatabase()
        {
            invalidFileNameChars = new HashSet<char>() { ‘\0‘, ‘ ‘, ‘.‘, ‘$‘, ‘/‘, ‘\\‘ };
            foreach (var c in Path.GetInvalidPathChars()) { invalidFileNameChars.Add(c); }
            foreach (var c in Path.GetInvalidFileNameChars()) { invalidFileNameChars.Add(c); }
        }

        /// <summary>
        /// 文件数据库
        /// </summary>
        /// <param name="directory">数据库文件所在目录</param>
        protected FileDatabase(string directory)
        {
            MyDirectory = directory;
        }

        public FileDatabase()
        {

        }

        #endregion

        #region Properties

        /// <summary>
        /// 数据库文件所在目录
        /// </summary>
        public virtual string MyDirectory { get; protected set; }

        /// <summary>
        /// 文件扩展名
        /// </summary>
        public virtual string FileExtension { get; set; }

        public virtual bool IsIndent { get; set; }

        #endregion

        #region Public Methods

        /// <summary>
        /// 保存文档
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="id">文档ID</param>
        /// <param name="document">文档对象</param>
        /// <returns>文档ID</returns>
        public virtual string Save(string id, TEntity document)
        {
            if (string.IsNullOrEmpty(id))
                throw new ArgumentNullException("id");

            if (document == null)
                throw new ArgumentNullException("document");

            Delete(id);

            try
            {
                string fileName = GenerateFileFullPath(id);
                string output = Serialize(document, IsIndent);

                lock (operationLock)
                {
                    System.IO.FileInfo info = new System.IO.FileInfo(fileName);
                    System.IO.Directory.CreateDirectory(info.Directory.FullName);
                    System.IO.File.WriteAllText(fileName, output);
                }
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  string.Format(CultureInfo.InvariantCulture,
                  "Save document failed with id [{0}].", id), ex);
            }

            return id;
        }

        /// <summary>
        /// 根据文档ID查找文档
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="id">文档ID</param>
        /// <returns>文档对象</returns>
        public virtual TEntity FindOneById(string id)
        {
            if (string.IsNullOrEmpty(id))
                throw new ArgumentNullException("id");

            try
            {
                string fileName = GenerateFileFullPath(id);
                if (File.Exists(fileName))
                {
                    string fileData = File.ReadAllText(fileName);
                    return Deserialize(fileData);
                }

                return default(TEntity);
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  string.Format(CultureInfo.InvariantCulture,
                  "Find document by id [{0}] failed.", id), ex);
            }
        }

        /// <summary>
        /// 查找指定类型的所有文档
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <returns>文档对象序列</returns>
        public virtual IEnumerable<TEntity> FindAll()
        {
            try
            {
                List<TEntity> list = new List<TEntity>();

                if (Directory.Exists(GenerateFilePath()))
                {
                    string[] files = System.IO.Directory.GetFiles(
                      GenerateFilePath(),
                      "*." + FileExtension,
                      SearchOption.TopDirectoryOnly);

                    foreach (string fileName in files)
                    {
                        string fileData = File.ReadAllText(fileName);
                        TEntity document = Deserialize(fileData);
                        if (document != null)
                        {
                            list.Add(document);
                        }
                    }
                }

                return list;
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  "Find all documents failed.", ex);
            }
        }

        /// <summary>
        /// 根据指定文档ID删除文档
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="id">文档ID</param>
        public virtual void Delete(string id)
        {
            if (string.IsNullOrEmpty(id))
                throw new ArgumentNullException("id");

            try
            {
                string fileName = GenerateFileFullPath(id);
                if (File.Exists(fileName))
                {
                    lock (operationLock)
                    {
                        File.Delete(fileName);
                    }
                }
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  string.Format(CultureInfo.InvariantCulture,
                  "Delete document by id [{0}] failed.", id), ex);
            }
        }

        /// <summary>
        /// 删除所有指定类型的文档
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        public virtual void DeleteAll()
        {
            try
            {
                if (Directory.Exists(GenerateFilePath()))
                {
                    string[] files = System.IO.Directory.GetFiles(
                      GenerateFilePath(), "*." + FileExtension,
                      SearchOption.TopDirectoryOnly);

                    foreach (string fileName in files)
                    {
                        lock (operationLock)
                        {
                            File.Delete(fileName);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  "Delete all documents failed.", ex);
            }
        }

        /// <summary>
        /// 获取指定类型文档的数量
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <returns>文档的数量</returns>
        public virtual int Count()
        {
            try
            {
                if (Directory.Exists(GenerateFilePath()))
                {
                    string[] files = System.IO.Directory.GetFiles(
                      GenerateFilePath(),
                      "*." + FileExtension, SearchOption.TopDirectoryOnly);
                    if (files != null)
                    {
                        return files.Length;
                    }
                    else
                    {
                        return 0;
                    }
                }
                return 0;
            }
            catch (Exception ex)
            {
                throw new FileDatabaseException(
                  "Count all documents failed.", ex);
            }
        }

        #endregion

        #region Protected Methods

        /// <summary>
        /// 生成文件全路径
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="id">文档ID</param>
        /// <returns>文件路径</returns>
        protected virtual string GenerateFileFullPath(string id)
        {
            return Path.Combine(GenerateFilePath(),
              GenerateFileName(id));
        }

        /// <summary>
        /// 生成文件路径
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <returns>文件路径</returns>
        protected virtual string GenerateFilePath()
        {
            return Path.Combine(this.MyDirectory, typeof(TEntity).Name);
        }

        /// <summary>
        /// 生成文件名
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="id">文档ID</param>
        /// <returns>文件名</returns>
        protected virtual string GenerateFileName(string id)
        {
            if (string.IsNullOrEmpty(id))
                throw new ArgumentNullException("id");

            foreach (char c in id)
            {
                if (invalidFileNameChars.Contains(c))
                {
                    throw new FileDatabaseException(
                      string.Format(CultureInfo.InvariantCulture,
                      "The character ‘{0}‘ is not a valid file name identifier.", c));
                }
            }

            return string.Format(CultureInfo.InvariantCulture, "{0}.{1}", id, FileExtension);
        }

        /// <summary>
        /// 将指定的文档对象序列化至字符串
        /// </summary>
        /// <param name="value">指定的文档对象</param>
        /// <returns>文档对象序列化后的字符串</returns>
        protected abstract string Serialize(object value, bool isIndent = false);

        /// <summary>
        /// 将字符串反序列化成文档对象
        /// </summary>
        /// <typeparam name="TEntity">文档类型</typeparam>
        /// <param name="data">字符串</param>
        /// <returns>文档对象</returns>
        protected abstract TEntity Deserialize(string data);

        #endregion
    }

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三、存储架构的设计

1、基础设施的构建

　　数据库采用的是类似仓储的设计，这样对数据的管理比较直观，并且易用。什么是仓储，园内有很多博客有阐述，在此就不赘述了。

　　首先，要先有实体基类：

    /// <summary>
    ///     可持久到数据库的领域模型的基类。
    /// </summary>
    [Serializable]
    public abstract class EntityBase
    {
        #region 构造函数

        /// <summary>
        ///     数据实体基类
        /// </summary>
        protected EntityBase()
        {
        }

        #endregion
    }

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　　其次，要有仓储接口：

    /// <summary>
    /// 数据基础操作规范
    /// </summary>
    /// <typeparam name="TEntity"></typeparam>
    public interface IRepository<TEntity> 
        where TEntity : EntityBase
    {
        /// <summary>
        /// 添加实体并提交到数据服务器
        /// </summary>
        /// <param name="item">需要添加数据项</param>
        /// <returns>受影响条数</returns>
        int Insert(TEntity item);

        /// <summary>
        /// 移除实体并提交到数据服务器
        /// 如果表存在约束，需要先删除子表信息
        /// </summary>
        /// <param name="item">需要删除的数据项</param>
        /// <returns>受影响条数</returns>
        int Delete(TEntity item);

        /// <summary>
        /// 修改实体并提交到数据服务器
        /// </summary>
        /// <param name="item">需要修改的数据项</param>
        /// <returns>受影响条数</returns>
        int Update(TEntity item);

        /// <summary>
        /// 得到指定的实体集合（延时结果集）
        /// </summary>
        /// <returns>实体集合</returns>
        IQueryable<TEntity> GetModel();

        /// <summary>
        /// 根据主键得到实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        TEntity Find(params object[] id);
    }

View Code

2、基于json仓储的实现

　　json实体基类：

    /// <summary>
    /// Json实体基类
    /// </summary>
    public abstract class JsonEntity : EntityBase
    {
        private string id = PublicHelper.GuidGenerator();
        /// <summary>
        /// Json实体主键
        /// </summary>
        public string RootID
        {
            get { return id; }
            set { id = value; }
        }
    }

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　　json仓储接口：

    /// <summary>
    /// Json仓储接口
    /// </summary>
    /// <typeparam name="TEntity"></typeparam>
    public interface IJsonRepository<TEntity>
        : IRepository<TEntity>
        where TEntity : JsonEntity
    {
        /// <summary>
        /// 是否缩进
        /// </summary>
        bool IsIndent { get; set; }
        /// <summary>
        /// 按文件存储，直接删除所有文件
        /// </summary>
        void DeleteAll();
        int Count();
    }

View Code

　　json仓储的具体实现：

    /// <summary>
    /// json仓储
    /// </summary>
    public class JsonRepository<TEntity> :
        FileDatabase<TEntity>, IJsonRepository<TEntity>
        where TEntity : JsonEntity,new()
    {
        string m_Directory = AppDomain.CurrentDomain.BaseDirectory;

        public new bool IsIndent
        {
            get
            {
                return base.IsIndent;
            }

            set
            {
                base.IsIndent = value;
            }
        }

        public JsonRepository(string directory)
            :base(directory)
        {
            FileExtension = @"db";
            this.m_Directory = directory;
        }

        public JsonRepository()
        {
            FileExtension = @"db";
            MyDirectory = m_Directory;
        }

        public int Delete(TEntity item)
        {
            Delete(item.RootID);

            return 1;
        }

        public TEntity Find(params object[] id)
        {
            return FindOneById(id[0].ToString());
        }

        public IQueryable<TEntity> GetModel()
        {
            return FindAll().AsQueryable();
        }

        public int Insert(TEntity item)
        {
            Save(item.RootID, item);

            return 1;
        }

        public int Update(TEntity item)
        {
            Save(item.RootID, item);

            return 1;
        }

        protected override string Serialize(object value, bool isIndent = false)
        {
            return JsonHelper.Serialize(value, isIndent);
        }

        protected override TEntity Deserialize(string data)
        {
            return JsonHelper.Deserialize<TEntity>(data);
        }
    }

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四、工具类

　　PublicHelper：

    /// <summary>
    ///     公共辅助操作类
    /// </summary>
    public static class PublicHelper
    {
        #region 公共方法

        /// <summary>
        /// Guid生成器
        /// </summary>
        /// <returns></returns>
        public static string GuidGenerator()
        {
            return Guid.NewGuid().ToString("N");
        }
        #endregion
    }

View Code

　　JsonHelper:

    public class JsonHelper
    {
        /// <summary>
        /// 序列化json
        /// </summary>
        /// <param name="value">对象</param>
        /// <param name="isIndented">是否缩进</param>
        /// <returns></returns>
        public static string Serialize(object value, bool isIndented)
        {
            if (value == null)
            {
                throw new ArgumentNullException("value is null.");
            }

            return JsonConvert.SerializeObject(value, isIndented ? Formatting.Indented : Formatting.None);
        }

        /// <summary>
        /// 将字符反序列化成对象
        /// </summary>
        /// <typeparam name="TEntity">泛型对象</typeparam>
        /// <param name="data"></param>
        /// <returns></returns>
        public static TEntity Deserialize<TEntity>(string data)
        {
            if (string.IsNullOrEmpty(data))
            {
                throw new ArgumentNullException("data is null or empty.");
            }

            return JsonConvert.DeserializeObject<TEntity>(data);
        }
    }

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五、运行测试

　　测试代码：

    class Program
    {
        static void Main(string[] args)
        {
            IJsonRepository<Student> jsonRepository = new JsonRepository<Student>();

            jsonRepository.Insert(new Student()
            {
                SNo = 1,
                Name = "张三",
                Gender = "女",
                Age = 18,
            });

            jsonRepository.Insert(new Student()
            {
                SNo = 2,
                Name = "李四",
                Gender = "女",
                Age = 18,
            });

            jsonRepository.Insert(new Student()
            {
                SNo = 3,
                Name = "王二",
                Gender = "女",
                Age = 18,
            });

            var entities = jsonRepository.GetModel();

            foreach (var item in entities)
            {
                Console.WriteLine(item.ToString());
            }

            Console.ReadKey();
        }
    }

    public class Student:JsonEntity
    {
        /// <summary>
        /// 学号
        /// </summary>
        public int SNo { get; set; }
        /// <summary>
        /// 名称
        /// </summary>
        public string Name { get; set; }
        /// <summary>
        /// 性别
        /// </summary>
        public string Gender { get; set; }
        /// <summary>
        /// 年龄
        /// </summary>
        public int Age { get; set; }

        public override string ToString()
        {
            return string.Format("学号：{0};姓名：{1};性别：{2};年龄：{3}", this.SNo, this.Name, this.Gender, this.Age);
        }
    }