在本章中，我们将介绍NHibernate中的关系.让我们把注意力转向我们如何理解NHibernate中的关系.最简单的方法是从数据库的角度考虑关系.
我们将首先创建一个新的应用程序，我们在其中将在客户和订单实体之间建立一些关系.
我们要看的第一个关系是经典的收藏关系.
我们有一个订单集合的客户.
这是一对多的关系并且它在数据库中由2个表表示，订单表上有一个客户ID，我们有一个外键关系返回给客户.
首先我们需要创建一个数据库和两个表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它.
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.
以下图像显示订单表，您可以在其中查看返回给客户的外键关系.
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.
<?xml version = "1.0" encoding = "utf-8" ?> <configuration> <connectionStrings> <add name = "default" connectionString = "Data Source = (localdb)\MSSQLLocalDB;Initial Catalog = NHibernateDemo;Integrated Security = True;Connect Timeout = 30;Encrypt = False;TrustServerCertificate = False; ApplicationIntent = ReadWrite;MultiSubnetFailover = False"/> </connectionStrings> </configuration>
要在应用程序中安装NHibernate，请在NuGet Manager Console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中定义配置文件如下面的代码所示.
<xml version = "1.0" encoding = "utf-8" ?> <hibernate-configuration xmlns = "urn:nhibernate-configuration-2.2"> <session-factory> <property name = "connection.connection_string_name">default</property> <property name = "connection.driver_class"> NHibernate.Driver.SqlClientDriver </property> <property name = "dialect"> NHibernate.Dialect.MsSql2008Dialect </property> <property name = "show_sql">true</property> </session-factory> </hibernate-configuration>
在这个例子中，我们将使用两个域类，即客户和订单.
这是客户. cs文件实现，其中我们有两个类，一个是Customer类，另一个是Location类，其中对象用作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<Order>();
}
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<Order> 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类映射到Customer表.
<?xml version = "1.0" encoding = "utf-8" ?> <hibernate-mapping xmlns = "urn:nhibernate-mapping-2.2" assembly = "NHibernateDemo" namespace = "NHibernateDemo"> <class name = "Customer"> <id name = "Id"> <generator class = "guid.comb"/> </id> <property name = "FirstName"/> <property name = "LastName"/> <property name = "AverageRating"/> <property name = "Points"/> <property name = "HasGoldStatus"/> <property name = "MemberSince" type = "UtcDateTime"/> <property name = "CreditRating" type = "CustomerCreditRatingType"/> <component name = "Address"> <property name = "Street"/> <property name = "City"/> <property name = "Province"/> <property name = "Country"/> </component> </class> </hibernate-mapping>
我们还有一个订单类，这里是 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);
}
}
}我们还需要将Order类映射到数据库中的Order表，因此这里是 Order.hbm.xml 文件的实现.
<?xml version = "1.0" encoding = "utf-8" ?> <hibernate-mapping xmlns = "urn:nhibernate-mapping-2.2" assembly = "NHibernateDemo" namespace = "NHibernateDemo"> <class name = "Order" table = "`Order`"> <id name = "Id"> <generator class = "guid.comb"/> </id> <property name = "Ordered"/> <property name = "Shipped"/> <component name = "ShipTo"> <property name = "Street"/> <property name = "City"/> <property name = "Province"/> <property name = "Country"/> </component> <!--<many-to-one name = "Customer" column = "CustomerId" cascade = "save-update"/>--> </class> </hibernate-mapping>
在这里，我们将看一下一对一在这种情况下，客户和订单之间存在许多关系.我们在这里有我们的客户，我们正在创建一个新客户，您可以看到该集合已使用以下一对订单进行初始化.
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;
}所以我们将创建一个新客户，然后将其保存，保存后，我们将找到该ID，然后在另一个中重新加载主方法中的会话，如下面的程序所示.
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<Customer>(id);
Console.WriteLine("Reloaded:");
Console.WriteLine(reloaded);
tx.Commit();
}
Console.WriteLine("Press <ENTER> 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<Customer>(id);
Console.WriteLine("Reloaded:");
Console.WriteLine(reloaded);
tx.Commit();
}
Console.WriteLine("Press <ENTER> 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<SqlClientDriver>();
x.Dialect<MsSql2008Dialect>();
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，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 (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 <ENTER> to exit...
正如您所看到的，最初客户有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，可以看到我们没有映射实际订单集合.所以NHibernate一无所知.让我们继续添加它.
<?xml version = "1.0" encoding = "utf-8" ?> <hibernate-mapping xmlns = "urn:nhibernate-mapping-2.2" assembly = "NHibernateDemo" namespace = "NHibernateDemo"> <class name = "Customer"> <id name = "Id"> <generator class = "guid.comb"/> </id> <property name = "FirstName"/> <property name = "LastName"/> <property name = "AverageRating"/> <property name = "Points"/> <property name = "HasGoldStatus"/> <property name = "MemberSince" type = "UtcDateTime"/> <property name = "CreditRating" type = "CustomerCreditRatingType"/> <component name = "Address"> <property name = "Street"/> <property name = "City"/> <property name = "Province"/> <property name = "Country"/> </component> <set name = "Orders" table = "`Order`"> <key column = "CustomerId"/> <one-to-many class = "Order"/> </set> </class> </hibernate-mapping>
这是一个集合，此集合的名称是"Orders"，它存储在一个名为order的表中.我们需要指定一个键，它是外键的名称或查找订单.这些订单通过客户ID识别或属于客户.然后我必须注意，这是一对多关系，它与订单类有关.
我们还需要通过保存新客户订单稍微更改Main方法到数据库以及以下程序中显示.
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<Customer>(id);
Console.WriteLine("The orders were ordered by: ");
foreach (var order in reloaded.Orders) {
Console.WriteLine(order.Customer);
}
tx.Commit();
}
Console.WriteLine("Press <ENTER> to exit..."); Console.ReadLine();
}我们还指定了哪个客户订购了该特定产品.所以我们需要创建一个多对一的关系来将该订单与该客户联系起来.
所以让我们进入 Order.hbm.xml 文件并添加多对一，然后将客户字段和列命名为客户ID.
<?xml version = "1.0" encoding = "utf-8" ?> <hibernate-mapping xmlns = "urn:nhibernate-mapping-2.2" assembly = "NHibernateDemo" namespace = "NHibernateDemo"> <class name = "Order" table = "`Order`"> <id name = "Id"> <generator class = "guid.comb"/> </id> <property name = "Ordered"/> <property name = "Shipped"/> <component name = "ShipTo"> <property name = "Street"/> <property name = "City"/> <property name = "Province"/> <property name = "Country"/> </component> <many-to-one name = "Customer" column = "CustomerId"/> </class> </hibernate-mapping>
让我们再次运行此应用程序，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 <ENTER> to exit...
