XML数据库的尝试-白红宇

XML数据库的尝试

阅读量：5809 次

发布时间：2019-06-18

本文共 14796 字，大约阅读时间需要 49 分钟。

首先祝大家新年快乐.身体健康,平安就是福气.

对于一般的个人迷你项目,数据量不大的时候,完全没有必要使用数据库,管理数据使用XML就可以了.

自己尝试写了一个XML数据库,插入1w条小记录,大概3M大小,然后将一半数据进行更新,大约耗时3秒钟.

XML数据库其实就是一个内存数据库,数据都在内存里面,速度不慢.

然后由于是XML序列化的,其实ORM也不需要了.每个数据库文件保存一种格式的数据.

废话不说,上代码

先是数据模型:

/* * Created by SharpDevelop. * User: scs * Date: 2014/12/30 * Time: 14:07 *  * To change this template use Tools | Options | Coding | Edit Standard Headers. */using System;using DevKit.Common;namespace DevKit.HtmlUtility{    ///     /// Description of Class1.    /// 
    [Serializable]    public class CodeSnap    {        ///         /// 标题        /// 
        public string Title = string.Empty;        ///         /// 描述        /// 
        public string Descrpition = string.Empty;        ///         /// 类别        /// 
        public string Catalog = string.Empty;        ///         /// Tag        /// 
        public string Tag = string.Empty;        ///         /// 代码        /// 
        public string Code = string.Empty;        ///         /// 检索        /// 
        /// 检索关键字        /// 
              Boolean Search(string strKeyword)        {            return false;            }    }}

数据模型是领域的数据,但是删除标志,更新时间这些数据库使用的字段也是需要的.由于需要序列化,必须打上[Serializable]

///     /// 数据库记录    /// 
    [Serializable]    public class Model
      
           {        /// 
               /// 删除标志        /// 
        public Boolean IsDel;        /// 
               /// 统一编号        /// 
        public string DBId;        /// 
               /// 最后更新时间        /// 
        public DateTime LastUpdate;        /// 
               /// 数据        /// 
        public T DataRec;    }

最后是数据库引擎的代码,这里用到了深拷贝

///     /// 数据库引擎    /// 
    public class XmlDataBase
      
           {        /// 
               /// 数据库状态        /// 
        public string Status = "Close";        /// 
               /// 数据表        /// 
        List
       
        
         > list = new List
         
          
           >();        /// 
            /// 数据库文件 /// 
        string DBfilename = string.Empty;        /// 
            /// 数据库记录数[Without IsDel] /// 
        /// 
                   public int getCount()        {            return list.Count(x => {                return !x.IsDel;            });        }        /// 
            /// 数据库记录数[With IsDel] /// 
        /// 
                   public int getCountWithDel()        {            return list.Count;        }        /// 
            /// 新建并且打开数据库 /// 
        /// 
                   public XmlDataBase(string xmlfilename)        {            DBfilename = xmlfilename;            if (System.IO.File.Exists(xmlfilename)) {                list = Utility.LoadObjFromXml
           
            
             
              >>(DBfilename); } } /// 
               /// 压缩数据库 /// 
 public void Compress() { var Compresslist = new List
              
               
                >(); Func
                
                 
                  ,Boolean> inner = (x) => { return (!x.IsDel); }; Compresslist = list.FindAll(new Predicate
                  
                   
                    >(inner)); list = Compresslist; Commit(); } /// 
                     /// 添加 /// 
 /// 
                     public void AppendRec(T rec) { var dbrec = new Model
                    
                     (); dbrec.DBId = Guid.NewGuid().ToString(); dbrec.DataRec = Common.Utility.DeepCopy(rec); dbrec.LastUpdate = DateTime.Now; list.Add(dbrec); } /// 
                      /// 删除 /// 
 /// 
                      public void DelRec(Model
                     
                       rec) { rec.IsDel = true; UpdateDB(Utility.DeepCopy(rec)); } /// 
                       /// 更新 /// 
 /// 
                       public void UpdataRec(Model
                      
                        rec) { UpdateDB(Utility.DeepCopy(rec)); } /// 
                        /// 数据的修改 /// 
 /// 
                       传递过来对象的深拷贝 void UpdateDB(Model
                       
                         rec) { for (int i = 0; i < list.Count; i++) { if (rec.DBId == list[i].DBId) { rec.LastUpdate = DateTime.Now; //不允许内部数据使用外部数据的指针引用 //这里使用深拷贝 list[i] = rec; break; } } } /// 
                         /// 提交更新 /// 
 public void Commit() { Utility.SaveObjAsXml(DBfilename, list); } /// 
                         /// 检索 /// 
 /// 
                         /// 
                        
                         数据对象的深拷贝
                         public List
                        
                         
                          > Search(Func
                          
                            SearchMethod) { Func
                           
                            
                             ,Boolean> inner = (x) => { return (SearchMethod(x.DataRec) && !x.IsDel); }; List
                             
                              
                               > t = new List
                               
                                
                                 >(); foreach (Model
                                 
                                   element in list.FindAll(new Predicate
                                  
                                   
                                    >(inner))) { //这里也是将数据的副本给与外部 t.Add(Utility.DeepCopy(element)); } return t; } }

数据库内部有一个列表,列表里面存放着数据记录,每个数据记录包括[业务数据]和[数据库信息]

数据的读取,给外部的是一个数据的深拷贝,这样的话,保证了外部对于数据的修改不会影响内部数据.

在传统的数据库中,一般都是通过TCP协议交换数据的,所以,数据其实也是一个深拷贝.

读取如此,保存数据也是将列表替换为一个外部对象的深拷贝.

每次保存数据的时候,其实是将所有的数据都写入数据XML文件中,当然,数据量少的前提下,这样做是可以的.

下面是一个使用的例子:数据库的New语句

Common.XmlDataBase
      
        db= new Common.XmlDataBase
       
        (@"C:\中和软件\CodeSnap.xml");;

void BtnAppendClick(object sender, EventArgs e)        {            Stopwatch x = new Stopwatch();            x.Start();            for (int i = 0; i < 9999; i++) {                var r = new CodeSnap();                r.Title = "Title" + i.ToString();                r.Descrpition = "Descrpition";                r.Tag = "Tag";                r.Code = "Code";                db.AppendRec(r);            }            db.Commit();            var t = db.Search((m) => {                return true;            });            for (int i = 0; i < t.Count; i++) {                if (i % 2 == 1) {                    t[i].DataRec.Title = "New Title";                    db.UpdataRec(t[i]);                }            }            db.Commit();            x.Stop();            MessageBox.Show(x.Elapsed.ToString());        }

这个只是一个XML数据的雏形,原代码基本上都在这里了.

可以改进的地方大概如下:NameSpace这些XML特有的属性的去除.

现在Key是用GUID的,这个东西也蛮大的,如果不考虑压缩数据库的问题,可以使用数字连番.

(如果使用数字连番的话,由于压缩数据库会改变数据记录数,可能出现主健重复的问题)

其他压缩,例如时间,现在使用标准的DateTime.Now,所以时间也很冗长.以后可以将时间格式化后,保存为文字列.


      
       false
          
      
       ef65bff8-4951-464d-bd8f-432f1148b9f8
          
      
       2014-12-31T11:02:43.5750566+08:00

当然,XML也可以换成JSON的,这样的话,数据可以更小,但是JSON操作还不是NET内置的功能,所以暂时不使用.

里面用到的XML操作和深拷贝代码如下

}        ///         /// 保存对象        /// 
        public static void SaveObjAsXml
      
       (string filename, T Obj)        {            var xml = new XmlSerializer(typeof(T));            var writer = new StreamWriter(filename);            xml.Serialize(writer, Obj);            writer.Close();        }        /// 
               /// 读取对象        /// 
        /// 
               /// 
               /// 
               public static T LoadObjFromXml
       
        (string filename)        {            var xml = new XmlSerializer(typeof(T));            var reader = new StreamReader(filename);            T obj = (T)xml.Deserialize(reader);            reader.Close();            return obj;        }        /// 
                /// 深拷贝        /// 
        /// 
                /// 
                public static T DeepCopy
        
         (T obj){            BinaryFormatter bFormatter = new BinaryFormatter();            MemoryStream stream = new MemoryStream();            bFormatter.Serialize(stream, obj);            stream.Seek(0, SeekOrigin.Begin);            return (T)bFormatter.Deserialize(stream);        }

出处：https://www.cnblogs.com/TextEditor/p/4195361.html

完整代码参考：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Xml.Serialization;using System.IO;using System.Runtime.Serialization.Formatters.Binary;using System.Xml;namespace ConsoleApplication1.xml{    ///     /// 数据库记录    /// 
    [Serializable]    public class Model
      
           {        /// 
               /// 删除标志        /// 
        public Boolean IsDel;        /// 
               /// 统一编号        /// 
        public string DBId;        /// 
               /// 最后更新时间        /// 
        public DateTime LastUpdate;        /// 
               /// 数据        /// 
        public T DataRec;    }    /// 
           /// 数据库引擎    /// 
    public class XmlDataBase
       
            {        /// 
                /// 数据表        /// 
        List
        
         
          > list = new List
          
           
            >(); /// 
             /// 数据库文件 /// 
 string DBfilename = string.Empty; /// 
             /// 数据库状态 /// 
 public string Status = "Close"; /// 
             /// 数据库记录数[Without IsDel] /// 
 /// 
             public int getCountWithoutDel() { Refresh(); return list.Count(x => !x.IsDel); } /// 
             /// 数据库记录数[With All] /// 
 /// 
             public int getCountWithAll() { Refresh(); return list.Count; } /// 
             /// 新建并且打开数据库 /// 
 /// 
             public XmlDataBase(string xmlfilename) { DBfilename = xmlfilename; if (System.IO.File.Exists(DBfilename)) { list = LoadObjFromXml
            
             
              
               >>(DBfilename); } } /// 
                /// 刷新数据 /// 
 public void Refresh() { //非静态，所以，可能在其他地方发生了数据更新 if (System.IO.File.Exists(DBfilename)) { list = LoadObjFromXml
               
                
                 
                  >>(DBfilename); } } /// 
                   /// 压缩数据库,清理已经删除的记录 /// 
 public void Compress() { var Compresslist = new List
                  
                   
                    >(); Func
                    
                     
                      , Boolean> inner = (x) => (!x.IsDel); Compresslist = list.FindAll(new Predicate
                      
                       
                        >(inner)); list = Compresslist; Commit(); } /// 
                         /// 添加 /// 
 /// 
                         public void AppendRec(T rec) { var dbrec = new Model
                        
                         (); dbrec.DBId = Guid.NewGuid().ToString(); dbrec.DataRec = DeepCopy(rec); dbrec.LastUpdate = DateTime.Now; list.Add(dbrec); } /// 
                          /// 删除 /// 
 /// 
                          public void DelRecord(Model
                         
                           rec) { rec.IsDel = true; UpdateDB(DeepCopy(rec)); } /// 
                           /// 删除制定编号数据 /// 
 /// 
                           public void DelRecordByDBID(string DBId) { for (int i = 0; i < list.Count; i++) { if (DBId == list[i].DBId) { list[i].IsDel = true; list[i].LastUpdate = DateTime.Now; break; } } } /// 
                           /// 更新 /// 
 /// 
                           public void UpdataRec(Model
                          
                            rec) { UpdateDB(DeepCopy(rec)); } /// 
                            /// 数据的修改 /// 
 /// 
                           传递过来对象的深拷贝 private void UpdateDB(Model
                           
                             rec) { for (int i = 0; i < list.Count; i++) { if (rec.DBId == list[i].DBId) { rec.LastUpdate = DateTime.Now; //不允许内部数据使用外部数据的指针引用,这里使用深拷贝 list[i] = rec; break; } } } /// 
                             /// 提交更新 /// 
 public void Commit() { SaveObjAsXml(DBfilename, list); } /// 
                             /// 检索 /// 
 /// 
                             /// 
                            
                             数据对象的深拷贝
                             public List
                            
                             
                              > SearchAsDBRecords(Func
                              
                                SearchMethod) { Refresh(); Func
                               
                                
                                 , Boolean> inner = (x) => (SearchMethod(x.DataRec) && !x.IsDel); var t = new List
                                 
                                  
                                   >(); foreach (Model
                                   
                                     element in list.FindAll(new Predicate
                                    
                                     
                                      >(inner))) { //这里也是将数据的副本给与外部 t.Add(DeepCopy(element)); } return t; } /// 
                                       /// 检索（根据数据号） /// 
 /// 
                                      数据号 /// 
                                       public Model
                                      
                                        SearchAsDBRecordByDBID(string DBID) { Refresh(); Model
                                       
                                         result = list.Find((x) => x.DBId == DBID && !x.IsDel); if (result != null) return DeepCopy(result); return null; } /// 
                                         /// 检索,（如果只是获取T对象列表） /// 
 /// 
                                         /// 
                                        
                                         数据对象的深拷贝
                                         public List
                                        
                                          SearchAsObjRecords(Func
                                         
                                           SearchMethod) { Refresh(); Func
                                          
                                           
                                            , Boolean> inner = (x) => (SearchMethod(x.DataRec) && !x.IsDel); var t = new List
                                            
                                             (); foreach (Model
                                             
                                               element in list.FindAll(new Predicate
                                              
                                               
                                                >(inner))) { //这里也是将数据的副本给与外部 t.Add(DeepCopy(element.DataRec)); } return t; } /// 
                                                 /// 检索（根据数据号）（如果只是获取T对象） /// 调用前请使用IsRecordExist函数确认数据是否存在 /// 
 /// 
                                                数据号 /// 
                                                 public T SearchAsObjRecordByDBID(string DBID) { Refresh(); T t = default(T); Model
                                                
                                                  result = list.Find((x) => x.DBId == DBID); t =DeepCopy(result.DataRec); return t; } /// 
                                                  /// 是否存在数据 /// 
 /// 
                                                  /// 
                                                  public bool IsRecordExists(Func
                                                 
                                                   SearchMethod) { Func
                                                  
                                                   
                                                    , Boolean> inner = (x) => (SearchMethod(x.DataRec) && !x.IsDel); return list.FindAll(new Predicate
                                                    
                                                     
                                                      >(inner)).Count != 0; } /// 
                                                       /// 是否存在指定番号数据 /// 
 /// 
                                                       /// 
                                                       public bool IsRecordExistsByDBID(string DBID) { Func
                                                      
                                                       
                                                        , Boolean> inner = (x) => (x.DBId == DBID && !x.IsDel); return list.FindAll(new Predicate
                                                        
                                                         
                                                          >(inner)).Count != 0; } /// 
                                                           /// 保存对象 /// 
 /// 
                                                           /// 
                                                           private static void SaveObjAsXml
                                                          
                                                           (string filename, T Obj) { var settings = new XmlWriterSettings(); settings.Indent = true; //NewLineChars对于String属性的东西无效 //这是对于XML中换行有效， //String的换行会变成Console的NewLine /n settings.NewLineChars = System.Environment.NewLine; var xml = new XmlSerializer(typeof(T)); var writer = XmlWriter.Create(filename, settings); var ns = new XmlSerializerNamespaces(); ns.Add("", ""); xml.Serialize(writer, Obj, ns); writer.Close(); } /// 
                                                            /// 读取对象 /// 
 /// 
                                                            /// 
                                                            /// 
                                                            private static T LoadObjFromXml
                                                           
                                                            (string filename) { var setting = new XmlReaderSettings(); var xml = new XmlSerializer(typeof(T)); var reader = XmlReader.Create(filename, setting); T obj = (T)xml.Deserialize(reader); reader.Close(); return obj; } /// 
                                                             /// 深拷贝 /// 
 /// 
                                                             /// 
                                                             private static T DeepCopy
                                                            
                                                             (T obj) { var bFormatter = new BinaryFormatter(); var stream = new MemoryStream(); bFormatter.Serialize(stream, obj); stream.Seek(0, SeekOrigin.Begin); return (T)bFormatter.Deserialize(stream); } }}

View Code

对象定义格式如下：

// 模式一using System;namespace ConsoleApplication1.xml{    ///     /// Description of Class1.    /// 
    [Serializable]    public class CodeSnap    {        ///         /// 标题        /// 
        public string Title = string.Empty;        ///         /// 描述        /// 
        public string Descrpition = string.Empty;        ///         /// 类别        /// 
        public string Catalog = string.Empty;        ///         /// Tag        /// 
        public string Tag = string.Empty;        ///         /// 代码        /// 
        public string Code = string.Empty;        ///         /// 检索        /// 
        /// 检索关键字        /// 
             public Boolean Search(string strKeyword)        {            return false;            }    }}// 模式二using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace ConsoleApplication1.xml{    [Serializable]    public class CodeBook    {        private string bName;        public string BookName        {            get { return bName; }            set { bName = value; }        }        private string bAnthor;        public string Anthor        {            get { return bAnthor; }            set { bAnthor = value; }        }                private int _price;        public int Price        {            get { return _price; }            set { _price = value; }        }    }}

调用方式参考：

xml.XmlDataBase
     
       db = new xml.XmlDataBase
      
       (@"C:\temp\CodeSnap.xml");            for (int i = 0; i < 4; i++)            {                var r = new xml.CodeSnap();                r.Title = "Title" + i.ToString();                r.Descrpition = "Descrpition";                r.Tag = "Tag";                r.Code = "Code";                db.AppendRec(r);            }            //db.Commit();            xml.XmlDataBase
       
         db1 = new xml.XmlDataBase
        
         (@"C:\temp\book.xml");            for (int i = 0; i < 5; i++)            {                var r = new xml.CodeBook();                r.Anthor = "anth " + i;                r.BookName = " book " + i;                r.Price = i;                db1.AppendRec(r);            }            //db1.Commit();            var t = db1.SearchAsDBRecords((m) =>            {                return true;            });            var bbb = t.FindAll((ss) => {
   return ss.DataRec.Price > 10;});            for (int i = 0; i < t.Count; i++)            {                if (i % 2 == 1)                {                    //xml.CodeBook b = t[i];                    //t[i].Price += 10;                    t[i].DataRec.Price += 10;                    //db1.UpdataRec(t[i]);                }                if (i==3)                {                    //db1.DelRecordByDBID(t[i].DBId);                    db1.DelRecord(t[i]);                }                Console.WriteLine(db1.Status);            }            db1.Commit();            Console.WriteLine(db1.getCountWithAll());            db1.Compress();