一起谈.NET技术，NHibernate3剖析：Mapping篇之ConfORM实战(3):OneToOne语义 狼人:

　　ConfORM概述

　　在ConfORM实战(1):概览中，描述了ConfORM简单使用。在ConfORM实战(2):原理中介绍了ConfORM的基本实现原理。如果你不熟悉ConfORM请查看前几篇文章，你也可以到http://code.google.com/p/codeconform/获取ConfORM。

　　在这之前，我们需要为HbmMapping写AsString()扩展方法：用于输出HbmMapping对象的Mapping，用于学习测试使用，具体代码参考这里。

　　在Domain设计中，关联关系有单向关联和双向关联两种，那么一对一我们可以分为单向一对一关联(Unidirectional one-to-one)、双向一对一主键关联(Bidirectional one-to-one (primary key association))、双向一对一外键关联(Bidirectional one-to-one (foreign key association))三种情况。这篇使用ConfORM“映射”这些Domain实例吧。

　　One-to-One语义

　　我们使用ObjectRelationalMapper类中的OneToOne方法定义两个对象一对一关系。

　　单向一对一关联(Unidirectional one-to-one)

　　1.Domain

　　设计单向一对一关联Domain实例，Person对象和Address对象，人有一个地址。

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Address Address { get; set; }
}

public class Address
{
    public int Id { get; set; }
    public string Street { get; set; }
    public int CivicNumber { get; set; }
}

　　2.ConfORM

　　使用ConfORM来配置Domain，使之编译生成我们需要的HbmMapping对象。(注意黑体)

[Test]
public void UnidirectionalOneToOneMappingDemo()
{
    //show how work with one-to-one and how ConfORM understands OOP
    var orm = new ObjectRelationalMapper();
    var mapper = new Mapper(orm);
    var entities = new[] { typeof(Person), typeof(Address) };
    //use the definition of table-to-class strategy class by class
    orm.TablePerClass(entities);
    // Defining relations
    orm.OneToOne<Person, Address>();
    // Show the mapping to the console
    var mapping = mapper.CompileMappingFor(entities);
    Console.Write(mapping.AsString());
}

　　3.Mapping

　　上面测试输出HbmMapping的映射字符串，如果你使用ReSharper或者TestDriven.Net工具测试，你可以看见下面输出：

　　4.原理

　　对于单向一对一关联，实际就是设置IManyToOneMapper，ConfORM会在IPatternsAppliersHolder的ManyToOne和ManyToOnePath集合中匹配对应模式适配器，即匹配UnidirectionalOneToOneUniqueCascadeApplier模式适配器，进行相应操作。

　　UnidirectionalOneToOneUniqueCascadeApplier：应用IManyToOneMapper.Unique(true)和ManyToOneMapper.Cascade(applyCascade.HasValue?applyCascade.Value : Cascade.All)。

　　双向一对一主键关联(Bidirectional one-to-one (primary key association))

　　1.Domain

　　设计双向一对一关联Domain实例，Person对象和Address对象，人有一个地址，地址有一个人。

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Address Address { get; set; }
}

public class Address
{
    public int Id { get; set; }
    public Person Person { get; set; }
    public string Street { get; set; }
    public int CivicNumber { get; set; }
}

　　2.ConfORM

　　使用ConfORM来配置Domain，使之编译生成我们需要的HbmMapping对象。其实这个代码和上面的一样：

[Test]
public void BidirectionalOneToOneMappingDemo1()
{
    //show how work with one-to-one and how ConfORM understands OOP
    var orm = new ObjectRelationalMapper();
    var mapper = new Mapper(orm);
    var entities = new[] { typeof(Person), typeof(Address) };
    //use the definition of table-to-class strategy class by class
    orm.TablePerClass(entities);
    // Defining relations
    orm.OneToOne<Person, Address>();
    //or orm.OneToOne<Address,Person>();
    // Show the mapping to the console
    var mapping = mapper.CompileMappingFor(entities);
    Console.Write(mapping.AsString());
}

　　3.Mapping

　　测试生成字符串：

　　4.原理

　　对于双向一对一关联，实际就是设置IOneToOneMapper，ConfORM会在IPatternsAppliersHolder的OneToOne和OneToOnePath集合中匹配对应模式适配器，即匹配到以下三个模式适配器，进行相应操作。

　　BidirectionalPrimaryKeyAssociationMasterOneToOneApplier：应用IOneToOneMapper.Cascade(Cascade.All)

　　BidirectionalOneToOneAssociationPoidApplier：应用IIdMapper.Generator(Generators.Foreign(BidirectionalOneToOneOrNull(subject.ReflectedType)))

　　BidirectionalPrimaryKeyAssociationSlaveOneToOneApplier：应用IOneToOneMapper.Constrained(true)

　　双向一对一外键关联(Bidirectional one-to-one (foreign key association))

　　Domain与双向一对一主键关联(Bidirectional one-to-one (primary key association))相同。

　　2.ConfORM

　　配置Domain，注意黑体：

[Test]
public void BidirectionalOneToOneMappingDemo2()
{
    //show how work with one-to-one and how ConfORM understands OOP
    var orm = new ObjectRelationalMapper();
    var mapper = new Mapper(orm);
    var entities = new[] { typeof(Person), typeof(Address) };
    //use the definition of table-to-class strategy class by class
    orm.TablePerClass(entities);
    // Defining relations
    orm.ManyToOne<Person, Address>();
    orm.OneToOne<Address, Person>();
    // Show the mapping to the console
    var mapping = mapper.CompileMappingFor(entities);
    Console.Write(mapping.AsString());
}

　　3.Mapping

　　测试生成字符串：

　　4.原理

　　类似的，匹配到以下模式适配器：

　　BidirectionalForeignKeyAssociationManyToOneApplier：应用IManyToOneMapper.Unique(true)和IManyToOneMapper.Cascade(Cascade.All)

　　BidirectionalForeignKeyAssociationOneToOneApplier：应用IOneToOneMapper.PropertyReference(GetPropertyOf(manyToOneSideType, oneToOneSideType))

　　BidirectionalPrimaryKeyAssociationMasterOneToOneApplier：应用IOneToOneMapper..Cascade(Cascade.All)

　　结语

　　这篇文章展示ConfORM的One-to-One语义应用，映射了三种One-to-One映射。

　　参考资料

　　Fabio Maulo：ConfORM:“Mapping” One-To-One