XPO:Session管理与缓存测试篇

之前整理了一下XPO在Session管理和缓存方面的一些资料(XPO:Session管理与缓存--机制篇)，但原文的例程还是有些含糊的地方，这两天抽空做了一下测试。若有不当或者不对的地方敬请不吝赐教。

XPO初始化的代码就不重复贴了，这里只贴上主要的代码。

测试中构建了2个简单的类，XpoUser和XpoOrder，一对多的关系。

using System;
using DevExpress.Xpo;

namespace Model
{
    public class XpoUser : XPObject
    {
        public XpoUser()
            : base()
        {
            // This constructor is used when an object is loaded from a persistent storage.
            // Do not place any code here.
        }

        public XpoUser(Session session)
            : base(session)
        {
            // This constructor is used when an object is loaded from a persistent storage.
            // Do not place any code here.
        }

        public override void AfterConstruction()
        {
            base.AfterConstruction();
            // Place here your initialization code.
        }

        private string _Name;
        public string Name
        {
            get
            {
                return _Name;
            }
            set
            {
                SetPropertyValue("Name", ref _Name, value);
            }
        }

        [Association("XpoUser-Orders")]
        public XPCollection<XpoOrder> Orders
        {
            get
            {
                return GetCollection<XpoOrder>("Orders");
            }
        }
    }
}

using System;
using DevExpress.Xpo;

namespace Model
{
    public class XpoOrder : XPObject
    {
        public XpoOrder()
            : base()
        {
            // This constructor is used when an object is loaded from a persistent storage.
            // Do not place any code here.
        }

        public XpoOrder(Session session)
            : base(session)
        {
            // This constructor is used when an object is loaded from a persistent storage.
            // Do not place any code here.
        }

        public override void AfterConstruction()
        {
            base.AfterConstruction();
            // Place here your initialization code.
        }

        private string _OrderID;
        public string OrderID
        {
            get
            {
                return _OrderID;
            }
            set
            {
                SetPropertyValue("OrderID", ref _OrderID, value);
            }
        }

        private XpoUser _User;
        [Association("XpoUser-Orders")]
        public XpoUser User
        {
            get
            {
                return _User;
            }
            set
            {
                SetPropertyValue("User", ref _User, value);
            }
        }
    }
}

做了两个测试，测试一的代码：

            ClearDB();
            StringBuilder sb = new StringBuilder();
            Session s1 = new Session();
            Session s2 = new Session();
            XpoUser user1 = new XpoUser(s1) { Name = "UserName" };
            user1.Save();
            XpoUser user2 = s2.FindObject<XpoUser>(new BinaryOperator("Name", "UserName"));
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            sb.AppendLine(Environment.NewLine + "Change user's name in Session 1");
            user1.Name = "New UserName";
            user1.Save();
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            sb.AppendLine(Environment.NewLine + "Create / Read something else(XpoRole) in Session 2");
            XpoRole role = new XpoRole(s2) { Name = "RoleName" };
            role.Save();
            role = s2.FindObject<XpoRole>(new BinaryOperator("Name", "RoleName"));
            sb.AppendLine(string.Format("Role name : {0}", role.Name));
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            sb.AppendLine(Environment.NewLine + "Create / Read another XpoUser in Session 2");
            XpoUser anotherUser = new XpoUser(s2) { Name = "Another User" };
            anotherUser.Save();
            anotherUser = s2.FindObject<XpoUser>(new BinaryOperator("Name", "Another User"));
            sb.AppendLine(string.Format("Another user's name : {0}", anotherUser.Name));
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            sb.AppendLine(Environment.NewLine + "Try to Save the user in Session 2, which is modified in Session 1");
            try
            {
                user2.Save();
            }
            catch (Exception ex)
            {
                sb.AppendLine(ex.Message);
            }
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            sb.AppendLine(Environment.NewLine + "Session.Reload(User) in Session 2");
            s2.Reload(user2);
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));

            txtResult.Text = sb.ToString();

输出的结果：

[Session 1] User's Name : UserName

[Session 2] User's Name : UserName

Change user's name in Session 1

[Session 1] User's Name : New UserName

[Session 2] User's Name : UserName

Create / Read something else(XpoRole) in Session 2

Role name : RoleName

[Session 1] User's Name : New UserName

[Session 2] User's Name : UserName

Create / Read another XpoUser in Session 2

Another user's name : Another User

[Session 1] User's Name : New UserName

[Session 2] User's Name : UserName

Try to Save the user in Session 2, which is modified in Session 1

Cannot persist the object. It was modified or deleted (purged) by another application.

[Session 1] User's Name : New UserName

[Session 2] User's Name : UserName

Session.Reload(User) in Session 2

[Session 1] User's Name : New UserName

[Session 2] User's Name : New UserName

可以看到：

2个不同Session里Load同一个object，确实是同一个object被传递给了2个Session，而并非该Object的任何副本。

在一个Session中对该Object做了修改后，其他Session除非Reload该对象，否则将永远无法获得其他Session对其做的改动。

同时，试图保存这个已经被其他Session所更改过的对象时会抛错。

测试2：

            ClearDB();
            StringBuilder sb = new StringBuilder();
            Session s1 = new Session();
            Session s2 = new Session();
            XpoUser user1 = new XpoUser(s1) { Name = "UserName" };
            XpoOrder order = new XpoOrder(s1) { OrderID = "#1", User = user1 };
            user1.Orders.Add(order);
            user1.Save();
            XpoUser user2 = s2.FindObject<XpoUser>(new BinaryOperator("Name", "UserName"));

            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));


            sb.AppendLine(Environment.NewLine + "Create a new order , change user's name and change Order1's ID to #3 in Session 1");
            order = s1.FindObject<XpoOrder>(new BinaryOperator("OrderID", "#1"));
            order.OrderID = "#3";
            order.Save();
            order = new XpoOrder(s1) { OrderID = "#2", User = user1 };
            order.Save();
            user1.Name = "New UserName";
            user1.Orders.Add(order);
            user1.Save();
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Session.Reload(User) in Session 2");
            s2.Reload(user2);
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Session.Reload(User, forceAggregatesReload) in Session 2");
            s2.Reload(user2, true);
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Load Order again in Session 2");
            order = s2.FindObject<XpoOrder>(new BinaryOperator("OrderID", "#3"));
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Session.Reload(Order, forceAggregatesReload) in Session 2");
            s2.Reload(order, true);
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Load Order2 in Session 2");
            order = s2.FindObject<XpoOrder>(new BinaryOperator("OrderID", "#2"));
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            sb.AppendLine(Environment.NewLine + "Session.Reload(Order2, forceAggregatesReload) in Session 2");
            s2.Reload(order, true);
            sb.AppendLine(string.Format("[Session 1] User's Name : {0}", user1.Name));
            sb.AppendLine(string.Format("[Session 1] User's Order : {0}", GetOrders(user1)));
            sb.AppendLine(string.Format("[Session 2] User's Name : {0}", user2.Name));
            sb.AppendLine(string.Format("[Session 2] User's Order : {0}", GetOrders(user2)));

            txtResult.Text = sb.ToString();

上面代码其实测试了几种不同的情况，分别注释掉后部几个代码块单独跑可以看得更清楚，这里只贴全部跑的结果：

[Session 1] User's Name : UserName

[Session 1] User's Order : #1 

[Session 2] User's Name : UserName

[Session 2] User's Order : #1 

Create a new order , change user's name and change Order1's ID to #3 in Session 1

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : UserName

[Session 2] User's Order : #1 

Session.Reload(User) in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #1 

Session.Reload(User, forceAggregatesReload) in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #1 

Load Order again in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #3 

Session.Reload(Order, forceAggregatesReload) in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #3 

Load Order2 in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #3 #2 

Session.Reload(Order2, forceAggregatesReload) in Session 2

[Session 1] User's Name : New UserName

[Session 1] User's Order : #3 #2 

[Session 2] User's Name : New UserName

[Session 2] User's Order : #3 #2 

在这个例子里，刷新User没有获得Order的变更，刷新Order也没有获得User的变更，更没有获得同一个User下其他Order的变更。

对于有一对多关系的结构来说，无论是刷新哪个对象，用不用forceAggregatesReload，都只会刷新到自己，不会对关联对象做出更新。

是bug还是对forceAggregatesReload的理解有误？

另一个问题是，在Session下并没有找到DropCache()方法，只有一个DropIdentityMap()方法，而调用这个方法以后，再Reload其他对象会抛错（对象已被Dispose）。在DevExpress的官网上大概搜了一下，也没找到什么说法。

从上面的测试结果来看，我很同意DevExpress建议的，对每一组互相关联的少量数据都使用一个单独的Session，“大方”的使用。在保持数据之间的逻辑关系不会被破坏的情况下，颗粒度越小越好。 单一Session里包含的数据越少，则这些数据的时间跨度就越小，而且一般说来也越快会被更新。如果想彻底抛弃一个Session的缓存重新加载的话，最好就直接new一个Session来做，而不要去Drop什么的了。