db4o虽然出来很久了，一直没怎么关注，今天随手试了下，对于小型应用还是不错的，至少省去了ORM的麻烦，一切皆对象，一切都变得那么自然。
下载地址:http://www.db4o.com/DownloadNow.aspx
优点:
1.使用简单，整个引擎只要一个dll(Db4objects.Db4o.dll)即能搞定(个人觉得可完全取代access用于某些小型应用)
2.数据库仅一个文件，方便部署
3.支持事务(文档上有提到的，不过我没测试过)
4.性能还过得去(10w以内的数据还可以接受，详见我的测试结果)
5.彻底忘记ORM吧，一切皆Object，还要什么ORM?
6.可同时用于.net与java平台
下面是测试代码:
db4o测试 by 菩提树下的杨过 http://yjmyzz.cnblogs.com
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Diagnostics;
using Db4objects.Db4o;
namespace GetStarted
{
class Program
{
static string DBFileName = "D:\\MyDoc\\db4o\\data\\demo.yap";
static void Main(string[] args)
{
//如果文件已经存在，先删除(免得原来的记录影响测试结果)
if (File.Exists(DBFileName)) { try { File.Delete(DBFileName); } catch (Exception e) { Console.WriteLine(e.Message.ToString()); } }
IObjectContainer db = Db4oFactory.OpenFile(DBFileName);//打开数据库(如果数据库文件不存在，将自动创建)
try
{
Pilot pilot1 = new Pilot("Michael Schumacher", 100);
db.Store(pilot1);//对象存入数据库(即传统意义上的insert操作)
Console.WriteLine("Stored {0}", pilot1);
Pilot pilot2 = new Pilot("Rubens Barrichello", 99);
db.Store(pilot2);//再存一个对象
Console.WriteLine("Stored {0}", pilot2);
Console.WriteLine("-----------------------------------------");
Pilot proto = new Pilot(null, 0);//如果要查询出所有Pilot，创建一个"empty"的Pilot即可
IObjectSet result = db.QueryByExample(proto);
ListResult(result);
Console.WriteLine("-----------------------------------------");
Pilot proto1 = new Pilot("Rubens Barrichello", 0);//按Name查询(比如有意思的是：第二个参数随便什么都行，另外第一个参数是区分大小写的)
IObjectSet result1 = db.QueryByExample(proto1);
ListResult(result1);
Console.WriteLine("-----------------------------------------");
Pilot proto2 = new Pilot(null, 99);//按points查询
IObjectSet result2 = db.QueryByExample(proto2);
ListResult(result2);
Console.WriteLine("-----------------------------------------");
IList<Pilot> pilots = db.Query<Pilot>(typeof(Pilot));//泛型的查询方法，貌似写法更简单自然
foreach (Pilot p in pilots)
{
Console.WriteLine(p);
}
Console.WriteLine("-----------------------------------------");
IList<Pilot> pilots2 = db.Query<Pilot>(new Predicate<Pilot>(c => c.Name == "Rubens Barrichello"));//按Name查询
foreach (Pilot p in pilots2)
{
Console.WriteLine(p);
}
Console.WriteLine("-----------------------------------------");
//更新数据
Pilot pilot3 = pilots2.FirstOrDefault();
Console.WriteLine("before update：" + pilot3);
pilot3.AddPoints(10);
db.Store(pilot3);
var _p = db.Query<Pilot>(new Predicate<Pilot>(c => c.Name == pilot3.Name)).FirstOrDefault();
Console.WriteLine("after update：" + _p);
Console.WriteLine("-----------------------------------------");
//删除数据
db.Delete(_p);
IList<Pilot> listAfterDel = db.Query<Pilot>(typeof(Pilot));//显示删除后的所有对象
foreach (Pilot p in listAfterDel)
{
Console.WriteLine(p);
}
Console.WriteLine("-----------------------------------------");
//大量数据插入测试
Stopwatch stopMatch = new Stopwatch();
stopMatch.Start();
int Count = 100000;//10w条数据
for (int i = 0; i < Count; i++)
{
Pilot pInsert = new Pilot(i.ToString(),i);
db.Store(pInsert);
}
stopMatch.Stop();
Console.WriteLine("{0}条记录插入共耗时{1}毫秒", Count, stopMatch.ElapsedMilliseconds);
stopMatch.Start();
IList<Pilot> lstAll = db.Query<Pilot>(typeof(Pilot));
stopMatch.Stop();
Console.WriteLine("{0}条记录查询共耗时{1}毫秒", Count, stopMatch.ElapsedMilliseconds);
stopMatch.Start();
foreach (Pilot p in lstAll)
{
p.AddPoints(1);
db.Store(p);
}
stopMatch.Stop();
Console.WriteLine("{0}条记录更新共耗时{1}毫秒", Count, stopMatch.ElapsedMilliseconds);
stopMatch.Start();
foreach (Pilot p in lstAll)
{
db.Delete(p);
}
stopMatch.Stop();
Console.WriteLine("{0}条记录删除共耗时{1}毫秒", Count, stopMatch.ElapsedMilliseconds);
}
catch (Exception e)
{
Console.WriteLine(e.Message.ToString());
}
finally
{
db.Close();
}
Console.ReadLine();
}
static void ListResult(IObjectSet result)
{
Console.WriteLine(result.Count);
foreach (object item in result)
{
Console.WriteLine(item);
}
}
}
public class Pilot
{
string _name;
int _points;
public Pilot(string name, int points)
{
_name = name;
_points = points;
}
public string Name { get { return _name; } }
public int Points { get { return _points; } }
public void AddPoints(int points)
{
_points += points;
}
public override string ToString()
{
return string.Format("{0}/{1}", _name, _points);
}
}
}
本机运行结果:
Stored Michael Schumacher/100
Stored Rubens Barrichello/99
-----------------------------------------
2
Michael Schumacher/100
Rubens Barrichello/99
-----------------------------------------
1
Rubens Barrichello/99
-----------------------------------------
1
Rubens Barrichello/99
-----------------------------------------
Michael Schumacher/100
Rubens Barrichello/99
-----------------------------------------
Rubens Barrichello/99
-----------------------------------------
before update：Rubens Barrichello/99
after update：Rubens Barrichello/109
-----------------------------------------
Michael Schumacher/100
-----------------------------------------
100000条记录插入共耗时6176毫秒
100000条记录查询共耗时6189毫秒
100000条记录更新共耗时15861毫秒
100000条记录删除共耗时23730毫秒