NHibernate-关系 - 芒果文档

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📜 NHibernate-关系

📅 最后修改于: 2020-11-19 05:37:55 🧑 作者: Mango

在本章中，我们将研究NHibernate中的关系。让我们将注意力转向如何理解NHibernate中的关系。最简单的方法是从数据库角度考虑关系。

我们将首先创建一个新的应用程序，在其中将在客户和订单实体之间创建一些关系。
我们要看的第一个关系是经典的收藏关系。
我们有一个带有订单集合的客户。
这是一对多的关系，在数据库中由2个表表示，在orders表上有一个客户ID，我们与客户之间有一个外键关系。

首先，我们需要创建一个数据库以及两个表Customer和Order。您可以通过在SQL Server资源管理器中指定以下查询来创建此查询。

USE [master] 
GO 
CREATE DATABASE [NHibernateDemo] 
GO 
USE [NHibernateDemo] 
GO

CREATE TABLE [dbo].[Customer]( 
   [Id] [uniqueidentifier] NOT NULL, 
   [FirstName] [nvarchar](100) NOT NULL, 
   [LastName] [nvarchar](100) NOT NULL, 
   [Points] [int] NULL, [HasGoldStatus] [bit] NULL, 
   [MemberSince] [date] NULL, 
   [CreditRating] [nchar](20) NULL, 
   [AverageRating] [decimal](18, 4) NULL, 
   [Street] [nvarchar](100) NULL, 
   [City] [nvarchar](100) NULL, 
   [Province] [nvarchar](100) NULL, 
   [Country] [nvarchar](100) NULL,
   PRIMARY KEY CLUSTERED ([Id] ASC) 
) 

GO 
CREATE TABLE [dbo].[Order]( 
   [Id] [uniqueidentifier] NOT NULL, 
   [CustomerId] [uniqueidentifier] NULL, 
   [Ordered] [datetime] NULL, 
   [Shipped] [datetime] NULL, 
   [Street] [nvarchar](100) NULL, 
   [City] [nvarchar](100) NULL, 
   [Province] [nvarchar](100) NULL, 
   [Country] [nvarchar](100) NULL, 
   PRIMARY KEY CLUSTERED ([Id] ASC) 
) 
GO

它将在数据库中创建两个表。下图显示了客户表。

客户表

下图显示了订单表，您可以在其中看到与客户之间的外键关系。

外键关系

我们需要在app.config文件中定义连接字符串，这是app.config文件的实现。

要在应用程序中安装NHibernate，请在NuGet Manager控制台窗口中运行以下命令。

install-package NHibernate

要配置NHibernate配置，我们需要在hibernate.cfg.xml文件中定义配置，如以下代码所示。

 
 
   
    
      default
        
      
         NHibernate.Driver.SqlClientDriver 
       
        
      
         NHibernate.Dialect.MsSql2008Dialect
       
        
      true

在此示例中，我们将处理两个域类，即Customer和Order。

这是Customer.cs文件实现，其中有两个类，一个是Customer类，另一个是Location类，在其中将对象用作Customer类中的地址。

using System; 
using System.Text; 
using Iesi.Collections.Generic;

namespace NHibernateDemo {
 
   public class Customer { 
      
      public Customer() { 
         MemberSince = DateTime.UtcNow; 
         Orders = new HashedSet(); 
      } 
      
      public virtual Guid Id { get; set; } 
      public virtual string FirstName { get; set; } 
      public virtual string LastName { get; set; } 
      public virtual double AverageRating { get; set; } 
      public virtual int Points { get; set; } 
        
      public virtual bool HasGoldStatus { get; set; }
      public virtual DateTime MemberSince { get; set; } 
      public virtual CustomerCreditRating CreditRating { get; set; } 
      public virtual Location Address { get; set; }
        
      public virtual ISet Orders { get; set; }
      public virtual void AddOrder(Order order) { Orders.Add(order); order.Customer = this; }
      
      public override string ToString() { 
         var result = new StringBuilder();
            
         result.AppendFormat("{1} {2} ({0})\r\n\tPoints: {3}\r\n\tHasGoldStatus:
            {4}\r\n\tMemberSince: {5} ({7})\r\n\tCreditRating: {6}\r\n\tAverageRating:
            {8}\r\n", Id, FirstName, LastName, Points, HasGoldStatus, MemberSince,
            CreditRating, MemberSince.Kind, AverageRating);
            result.AppendLine("\tOrders:"); 
         
         foreach(var order in Orders) { 
            result.AppendLine("\t\t" + order); 
         } 
            
         return result.ToString(); 
      } 
   }
   
   public class Location { 
      public virtual string Street { get; set; } 
      public virtual string City { get; set; } 
      public virtual string Province { get; set; } 
      public virtual string Country { get; set; } 
   }
   
   public enum CustomerCreditRating { 
      Excellent,
      VeryVeryGood, 
      VeryGood, 
      Good, 
      Neutral, 
      Poor, 
      Terrible 
   } 
}

这是映射文件Customer.hbm.xml ，其中Customer类被映射到Customer表。

我们还有一个Order类，这是Order.cs文件的实现。

using System; using Iesi.Collections.Generic;

namespace NHibernateDemo { 

   public class Order { 
      
      public virtual Guid Id { get; set; } 
      public virtual DateTime Ordered { get; set; } 
      public virtual DateTime? Shipped { get; set; }
      public virtual Location ShipTo { get; set; } 
      public virtual Customer Customer { get; set; }
      
      public override string ToString() { 
         return string.Format("Order Id: {0}", Id); 
      } 
   } 
}

多对一关系

我们还需要将Order类映射到数据库中的Order表，因此这是Order.hbm.xml文件的实现。

一对多关系

在这里，我们将研究客户与订单之间的一对多关系。我们在这里有客户，我们正在创建一个新客户，您可以看到该集合已通过以下一对订单进行了初始化。

private static Customer CreateCustomer() { 
   
   var customer = new Customer { 
      FirstName = "John", 
      LastName = "Doe", 
      Points = 100, 
      HasGoldStatus = true, 
      MemberSince = new DateTime(2012, 1, 1), 
      CreditRating = CustomerCreditRating.Good, 
      AverageRating = 42.42424242, 
      Address = CreateLocation() 
   }; 
   
   var order1 = new Order { 
      Ordered = DateTime.Now 
   }; 
   
   customer.AddOrder(order1); 
   var order2 = new Order { 
      Ordered = DateTime.Now.AddDays(-1), 
      Shipped = DateTime.Now, 
      ShipTo = CreateLocation() 
   }; 
   
   customer.AddOrder(order2); 
   return customer; 
}

因此，我们将创建一个新客户，然后保存它，保存后，我们将找到ID，然后在Main方法的另一个会话中重新加载它，如以下程序所示。

private static void Main() { 

   var cfg = ConfigureNHibernate(); 
   var sessionFactory = cfg.BuildSessionFactory();
   
   Guid id; 
   using(var session = sessionFactory.OpenSession()) 
    
   using(var tx = session.BeginTransaction()) { 
      var newCustomer = CreateCustomer(); 
      Console.WriteLine("New Customer:"); 
      Console.WriteLine(newCustomer);
      session.Save(newCustomer); 
      id = newCustomer.Id; 
      tx.Commit(); 
   }
   
   using(var session = sessionFactory.OpenSession()) 
    
   using(var tx = session.BeginTransaction()) { 
      var reloaded = session.Load(id); 
      Console.WriteLine("Reloaded:"); 
      Console.WriteLine(reloaded); 
      tx.Commit(); 
   }
   
   Console.WriteLine("Press  to exit..."); 
   Console.ReadLine(); 
}

这是完整的Program.cs文件实现。

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq;

namespace NHibernateDemo {
 
   internal class Program { 
    
      private static void Main() { 
        
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         
         Guid id; 
         using(var session = sessionFactory.OpenSession())
            
         using(var tx = session.BeginTransaction()) { 
            var newCustomer = CreateCustomer(); 
            Console.WriteLine("New Customer:"); 
            Console.WriteLine(newCustomer); 
            session.Save(newCustomer); 
            id = newCustomer.Id; 
            tx.Commit(); 
         } 
         
         using(var session = sessionFactory.OpenSession()) 
            
         using(var tx = session.BeginTransaction()) { 
            var reloaded = session.Load(id); 
            Console.WriteLine("Reloaded:"); 
            Console.WriteLine(reloaded); 
            tx.Commit();
         }
         
         Console.WriteLine("Press  to exit..."); 
         Console.ReadLine();
      }
      
      private static Customer CreateCustomer() { 
        
         var customer = new Customer { 
            FirstName = "John", 
            LastName = "Doe", 
            Points = 100, 
            HasGoldStatus = true, 
            MemberSince = new DateTime(2012, 1, 1), 
            CreditRating = CustomerCreditRating.Good, 
            AverageRating = 42.42424242, 
            Address = CreateLocation() 
         }; 
         
         var order1 = new Order { 
            Ordered = DateTime.Now
         }; 
         
         customer.AddOrder(order1); 
            
         var order2 = new Order { 
            Ordered = DateTime.Now.AddDays(-1), 
            Shipped = DateTime.Now, 
            ShipTo = CreateLocation() 
         }; 
         
         customer.AddOrder(order2); 
         return customer; 
      } 
      
      private static Location CreateLocation() { 
        
         return new Location { 
            Street = "123 Somewhere Avenue", 
            City = "Nowhere", 
            Province = "Alberta", 
            Country = "Canada" 
         }; 
      } 
      
      private static Configuration ConfigureNHibernate() { 
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x =&ht; { 
            x.ConnectionStringName = "default"; 
            x.Driver(); 
            x.Dialect(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; x.BatchSize = 10; 
         }); 
         
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   } 
}

运行此应用程序时，将看到以下输出。

New Customer:

John Doe (00000000-0000-0000-0000-000000000000)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Unspecified)
   CreditRating: Good
   AverageRating: 42.42424242

   Orders:
      Order Id: 00000000-0000-0000-0000-000000000000
      Order Id: 00000000-0000-0000-0000-000000000000

Reloaded:
John Doe (9b0fcf10-83f6-4f39-bda5-a5b800ede2ba)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Utc)
   CreditRating: Good
   AverageRating: 42.4242

   Orders:
Press  to exit...

如您所见，该客户最初有2个订单，但是当我们重新加载时，没有订单可见。如果查看customer.hbm.xml文件，则可以在此处看到我们没有映射实际的订单集合。因此，NHibernate对此一无所知。让我们继续添加它。

这是一个集合，此集合的名称为“订单”，存储在称为“订单”的表中。我们需要指定一个作为外键名称的键或查找订单。这些订单通过客户ID识别或属于客户。然后我必须指出，这是一对多的关系，它与订单类有关。

我们还需要通过将新的客户订单保存到数据库中来稍微更改Main方法，如以下程序所示。

private static void Main() { 

   var cfg = ConfigureNHibernate(); 
   var sessionFactory = cfg.BuildSessionFactory();
   
   Guid id; 
   using(var session = sessionFactory.OpenSession()) 
    
   using(var tx = session.BeginTransaction()) {
      var newCustomer = CreateCustomer(); 
      Console.WriteLine("New Customer:"); 
      Console.WriteLine(newCustomer);
      session.Save(newCustomer); 
      
      foreach (var order in newCustomer.Orders) { 
         session.Save(order); 
      } 
        
      id = newCustomer.Id; 
      tx.Commit(); 
   }
   
   using(var session = sessionFactory.OpenSession()) 
    
   using(var tx = session.BeginTransaction()) { 
      var reloaded = session.Load(id); 
      Console.WriteLine("The orders were ordered by: "); 
      
      foreach (var order in reloaded.Orders) { 
         Console.WriteLine(order.Customer); 
      } 
        
      tx.Commit(); 
   }
   Console.WriteLine("Press  to exit..."); Console.ReadLine();
}

我们还指定了哪个客户订购了该特定产品。因此，我们需要创建多对一关系，以将该订单与该客户联系起来。

因此，让我们进入Order.hbm.xml文件并添加多对一关系，然后用客户ID命名客户字段和列。

让我们再次运行该应用程序，现在您将看到以下输出。

New Customer:
John Doe (00000000-0000-0000-0000-000000000000)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Unspecified)
   CreditRating: Good
   AverageRating: 42.42424242

   Orders:
      Order Id: 00000000-0000-0000-0000-000000000000
      Order Id: 00000000-0000-0000-0000-000000000000

Reloaded:
John Doe (660a6f29-650e-4380-99e0-a5b800febbde)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Utc)
   CreditRating: Good
   AverageRating: 42.4242

   Orders:
      Order Id: 57314deb-e023-4e55-ac1e-a5b800febbe3
      Order Id: fc065683-d5f5-484b-ae42-a5b800febbe3

The orders were ordered by:
John Doe (660a6f29-650e-4380-99e0-a5b800febbde)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Utc)
   CreditRating: Good
   AverageRating: 42.4242

   Orders:
      Order Id: 57314deb-e023-4e55-ac1e-a5b800febbe3
      Order Id: fc065683-d5f5-484b-ae42-a5b800febbe3

John Doe (660a6f29-650e-4380-99e0-a5b800febbde)
   Points: 100
   HasGoldStatus: True
   MemberSince: 1/1/2012 12:00:00 AM (Utc)
   CreditRating: Good
   AverageRating: 42.4242

   Orders:
      Order Id: 57314deb-e023-4e55-ac1e-a5b800febbe3
      Order Id: fc065683-d5f5-484b-ae42-a5b800febbe3
        
Press  to exit...