NHibernate的关联映射(one-to-one,one-to-many,many-to-many)以及cascade分析
一、典型设置
cascade:(默认为none)级联。指明哪些操作会从对象级联到关联的对象。
inverse: (默认为false) 标记这个集合作为双向关联关系中的方向一端。在双向关联时才需要设置。在设为false的一端对cascade进行维护。处于性能的考虑,一般在数据少的一端或者被依赖端设置inverse="true",而让数据多的一段维护cascade。
1.one-to-one
1.1 数据库表结构
其中T_Person为主表,T_Employee为子表。T_Employee的PersonId参照T_Peson的PersonId。
1.2 示例映射类文件
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToOne
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Person
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _personid;
private string _name;
private Employee _employee;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Person()
{
_personid = 0;
_name = null;
_employee = null;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int PersonId
{
get { return _personid; }
set
{
_isChanged |= (_personid != value);
_personid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public Employee Employee
{
get { return _employee; }
set { _employee = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Person castObj = (Person) obj;
return (castObj != null) &&
(_personid == castObj.PersonId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_personid.GetHashCode();
return hash;
}
#endregion
}
}
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToOne
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Employee
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _personid;
private string _job;
private Person _person;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Employee()
{
_personid = 0;
_job = null;
_person = null;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int PersonId
{
get { return _personid; }
set
{
_isChanged |= (_personid != value);
_personid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Job
{
get { return _job; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Job", value, value.ToString());
_isChanged |= (_job != value);
_job = value;
}
}
public Person Person
{
get { return _person; }
set { _person = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Employee castObj = (Employee) obj;
return (castObj != null) &&
(_personid == castObj.PersonId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_personid.GetHashCode();
return hash;
}
#endregion
}
}
1.3 示例映射文件
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToOne.Person,DDLLY.TestNHibernate.TestAssociation"
table
="T_Person"
>
<
id
name
="PersonId"
column
="PersonId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
one-to-one
name
="Employee"
class
="DDLLY.TestNHibernate.TestAssociation.OneToOne.Employee,DDLLY.TestNHibernate.TestAssociation"
cascade
="all"
></
one-to-one
>
</
class
>
</
hibernate-mapping
>
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToOne.Employee,DDLLY.TestNHibernate.TestAssociation"
table
="T_Employee"
>
<
id
name
="PersonId"
column
="PersonId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="foreign"
>
<
param
name
="property"
>
Person
</
param
>
</
generator
>
</
id
>
<
property
column
="Job"
type
="String"
name
="Job"
length
="64"
/>
<
one-to-one
name
="Person"
class
="DDLLY.TestNHibernate.TestAssociation.OneToOne.Person,DDLLY.TestNHibernate.TestAssociation"
constrained
="true"
></
one-to-one
>
</
class
>
</
hibernate-mapping
>
1.4 说明
constrained(约束): 表明该类对应的表对应的数据库表,和被关联的对象所对应的数据库表之间,通过一个外键引用对主键进行约束。这个选项影响Save()和Delete()在级联执行时的先后顺序(也在schema export tool中被使用)。
property-ref: (可选) 指定关联类的一个属性,这个属性将会和本外键相对应。如果没有指定,会使用对方关联类的主键。
-
<generator class="foreign">:表示使用另外一个相关联的对象的标识符,来创建主健。T_Employee的PersonId来自T_Person的ParentId。
Employee依赖于Person,所以通常在Person设置cascade。
2.另一种one-to-one
2.1数据库表结构
其中T_Person1为主表,T_Employee1为子表。T_Employee1的PersonId设置唯一约束,参照T_Person1的PersonId。
2.2示例映射类文件
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToOne1
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Person
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _personid;
private string _name;
private Employee _employee;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Person()
{
_personid = 0;
_name = null;
_employee = null;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int PersonId
{
get { return _personid; }
set
{
_isChanged |= (_personid != value);
_personid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public Employee Employee
{
get { return _employee; }
set { _employee = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Person castObj = (Person) obj;
return (castObj != null) &&
(_personid == castObj.PersonId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_personid.GetHashCode();
return hash;
}
#endregion
}
}
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToOne1
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Employee
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _employeeId;
private string _job;
private Person _person;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Employee()
{
_employeeId = 0;
_job = null;
_person = null;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int EmployeeId
{
get { return _employeeId; }
set
{
_isChanged |= (_employeeId != value);
_employeeId = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Job
{
get { return _job; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Job", value, value.ToString());
_isChanged |= (_job != value);
_job = value;
}
}
public Person Person
{
get { return _person; }
set { _person = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Employee castObj = (Employee) obj;
return (castObj != null) &&
(_employeeId == castObj.EmployeeId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_employeeId.GetHashCode();
return hash;
}
#endregion
}
}
2.3示例映射文件
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToOne1.Person,DDLLY.TestNHibernate.TestAssociation"
table
="T_Person1"
>
<
id
name
="PersonId"
column
="PersonId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
one-to-one
name
="Employee"
class
="DDLLY.TestNHibernate.TestAssociation.OneToOne1.Employee,DDLLY.TestNHibernate.TestAssociation"
cascade
="all"
></
one-to-one
>
</
class
>
</
hibernate-mapping
>
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToOne1.Employee,DDLLY.TestNHibernate.TestAssociation"
table
="T_Employee1"
>
<
id
name
="EmployeeId"
column
="EmployeeId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Job"
type
="String"
name
="Job"
length
="64"
/>
<
many-to-one
name
="Person"
class
="DDLLY.TestNHibernate.TestAssociation.OneToOne1.Person,DDLLY.TestNHibernate.TestAssociation"
column
="PersonId"
unique
="true"
></
many-to-one
>
</
class
>
</
hibernate-mapping
>
2.4说明
这种one-to-one实际上是一种特殊的one-to-many,如果T_Employee1的PersonId不设置唯一约束,则可成为one-to-many。所以在T_Employee端设置many-to-one而不是one-to-one,记住要加上unique="true"表示唯一约束。
3.one-to-many
3.1 数据库表结构
T_Parent为主表,T_Child的ParentId参照T_Parent的ParentId。
注意:对于单向的one-to-many映射,cascade过程中会用到把T_Child表的ParentId设置为Null,所以ParentId应设为允许NULL;
而双向one-to-many映射,建议把T_Child的ParentI设置为不允许NULL
3.2 示例映射类文件(单向)
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
using
System.Collections;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToMany1
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Parent
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _parentid;
private string _name;
private IList _children;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Parent()
{
_parentid = 0;
_name = null;
_children = new ArrayList();
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int ParentId
{
get { return _parentid; }
set
{
_isChanged |= (_parentid != value);
_parentid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual IList Children
{
get { return _children; }
set
{
_isChanged |= (_children != value);
_children = value;
}
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Parent castObj = (Parent) obj;
return (castObj != null) &&
(_parentid == castObj.ParentId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_parentid.GetHashCode();
return hash;
}
#endregion
}
}
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToMany1
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Child
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _childid;
private string _name;
private int _parentid;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Child()
{
_childid = 0;
_name = null;
_parentid = 0;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int ChildId
{
get { return _childid; }
set
{
_isChanged |= (_childid != value);
_childid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual int ParentId
{
get { return _parentid; }
set
{
_isChanged |= (_parentid != value);
_parentid = value;
}
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Child castObj = (Child) obj;
return (castObj != null) &&
(_childid == castObj.ChildId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_childid.GetHashCode();
return hash;
}
#endregion
}
}
3.3 示例映射文件(单向)
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToMany1.Parent,DDLLY.TestNHibernate.TestAssociation"
table
="T_Parent"
>
<
id
name
="ParentId"
column
="ParentId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
bag
name
="Children"
cascade
="all"
lazy
="true"
>
<
key
column
="ParentId"
/>
<
one-to-many
class
="DDLLY.TestNHibernate.TestAssociation.OneToMany1.Child,DDLLY.TestNHibernate.TestAssociation"
/>
</
bag
>
</
class
>
</
hibernate-mapping
>
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToMany1.Child,DDLLY.TestNHibernate.TestAssociation"
table
="T_Child"
>
<
id
name
="ChildId"
column
="ChildId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
property
column
="ParentId"
type
="Int32"
name
="ParentId"
/>
</
class
>
</
hibernate-mapping
>
3.4 示例映射类文件(双向)
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
using
System.Collections;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToMany
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Parent
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _parentid;
private string _name;
private IList _children;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Parent()
{
_parentid = 0;
_name = null;
_children = new ArrayList();
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int ParentId
{
get { return _parentid; }
set
{
_isChanged |= (_parentid != value);
_parentid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual IList Children
{
get { return _children; }
set
{
_isChanged |= (_children != value);
_children = value;
}
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Parent castObj = (Parent) obj;
return (castObj != null) &&
(_parentid == castObj.ParentId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_parentid.GetHashCode();
return hash;
}
#endregion
}
}
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
namespace
DDLLY.TestNHibernate.TestAssociation.OneToMany
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Child
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _childid;
private string _name;
private Parent _parent;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Child()
{
_childid = 0;
_name = null;
_parent = null;
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int ChildId
{
get { return _childid; }
set
{
_isChanged |= (_childid != value);
_childid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Name
{
get { return _name; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Name", value, value.ToString());
_isChanged |= (_name != value);
_name = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual Parent Parent
{
get { return _parent; }
set
{
_isChanged |= (_parent != value);
_parent = value;
}
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Child castObj = (Child) obj;
return (castObj != null) &&
(_childid == castObj.ChildId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_childid.GetHashCode();
return hash;
}
#endregion
}
}
3.5 示例映射类文件(双向)
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToMany.Parent,DDLLY.TestNHibernate.TestAssociation"
table
="T_Parent"
>
<
id
name
="ParentId"
column
="ParentId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
bag
name
="Children"
cascade
="all"
inverse
="true"
lazy
="true"
>
<
key
column
="ParentId"
/>
<
one-to-many
class
="DDLLY.TestNHibernate.TestAssociation.OneToMany.Child,DDLLY.TestNHibernate.TestAssociation"
/>
</
bag
>
</
class
>
</
hibernate-mapping
>
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.OneToMany.Child,DDLLY.TestNHibernate.TestAssociation"
table
="T_Child"
>
<
id
name
="ChildId"
column
="ChildId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="Name"
type
="String"
name
="Name"
length
="64"
/>
<
many-to-one
name
="Parent"
column
="ParentId"
class
="DDLLY.TestNHibernate.TestAssociation.OneToMany.Parent,DDLLY.TestNHibernate.TestAssociation"
/>
</
class
>
</
hibernate-mapping
>
3.6 说明
在NHibernate配置文件中使用<set>, <list>, <map>, <bag>, <array> 和 <primitive-array>等元素来定义集合。<bag>是典型的一个,代码中我们用IList和它对应。我们以后会详细讲集合这个话题。
lazy表示允许延迟加载。表示在需要使用时才加载需要的数据。例如使用lazy时我们Load一个Parent他的Children为空,只有我们访问它的某一个Child时数据才会被加载;而不设置lazy我们Load一个Parent时其Children将同时加载。注意:使用lazy加载必须保证对应ISession的打开,否则懒加载会失败。
one-to-many可以设置单向和双向映射,设置单向时Child一段不设置many-to-one,而设置了ParentId的属性。
双向映射需要设置inverse而单向不需要。
单项映射在cascade时会对把T_Child的ParentId使用Update为Null的操作。
建议尽量使用双向映射。
4.many-to-many
4.1 数据库表结构
4.2 示例映射类文件
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
using
System.Collections;
namespace
DDLLY.TestNHibernate.TestAssociation.ManyToMany
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class User
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _userid;
private string _username;
private string _password;
private string _email;
private IList _roles;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public User()
{
_userid = 0;
_username = null;
_password = null;
_email = null;
_roles = new ArrayList();
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int UserId
{
get { return _userid; }
set
{
_isChanged |= (_userid != value);
_userid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string UserName
{
get { return _username; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for UserName", value, value.ToString());
_isChanged |= (_username != value);
_username = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Password
{
get { return _password; }
set
{
if (value != null)
if (value.Length > 32)
throw new ArgumentOutOfRangeException("Invalid value for Password", value, value.ToString());
_isChanged |= (_password != value);
_password = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string Email
{
get { return _email; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for Email", value, value.ToString());
_isChanged |= (_email != value);
_email = value;
}
}
public IList Roles
{
get { return _roles; }
set { _roles = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
User castObj = (User) obj;
return (castObj != null) &&
(_userid == castObj.UserId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_userid.GetHashCode();
return hash;
}
#endregion
}
}
/**/
/*
/*作者:DDL
/*联系:http://renrenqq.cnblogs.com/
*/
using
System;
using
System.Collections;
namespace
DDLLY.TestNHibernate.TestAssociation.ManyToMany
{
/**//// <summary>
///
/// </summary>
[Serializable]
public class Role
{
Private Members#region Private Members
private bool _isChanged;
private bool _isDeleted;
private int _roleid;
private string _rolename;
private IList _users;
#endregion
Default ( Empty ) Class Constuctor#region Default ( Empty ) Class Constuctor
/**//// <summary>
/// default constructor
/// </summary>
public Role()
{
_roleid = 0;
_rolename = null;
_users = new ArrayList();
}
#endregion // End of Default ( Empty ) Class Constuctor
Public Properties#region Public Properties
/**//// <summary>
///
/// </summary>
public virtual int RoleId
{
get { return _roleid; }
set
{
_isChanged |= (_roleid != value);
_roleid = value;
}
}
/**//// <summary>
///
/// </summary>
public virtual string RoleName
{
get { return _rolename; }
set
{
if (value != null)
if (value.Length > 64)
throw new ArgumentOutOfRangeException("Invalid value for RoleName", value, value.ToString());
_isChanged |= (_rolename != value);
_rolename = value;
}
}
public IList Users
{
get { return _users; }
set { _users = value; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsChanged
{
get { return _isChanged; }
}
/**//// <summary>
/// Returns whether or not the object has changed it's values.
/// </summary>
public bool IsDeleted
{
get { return _isDeleted; }
}
#endregion
Public Functions#region Public Functions
/**//// <summary>
/// mark the item as deleted
/// </summary>
public void MarkAsDeleted()
{
_isDeleted = true;
_isChanged = true;
}
#endregion
Equals And HashCode Overrides#region Equals And HashCode Overrides
/**//// <summary>
/// local implementation of Equals based on unique value members
/// </summary>
public override bool Equals(object obj)
{
if (this == obj) return true;
if ((obj == null) || (obj.GetType() != GetType())) return false;
Role castObj = (Role) obj;
return (castObj != null) &&
(_roleid == castObj.RoleId);
}
/**//// <summary>
/// local implementation of GetHashCode based on unique value members
/// </summary>
public override int GetHashCode()
{
int hash = 57;
hash = 27*hash*_roleid.GetHashCode();
return hash;
}
#endregion
}
}
4.3 示例映射文件
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.ManyToMany.User,DDLLY.TestNHibernate.TestAssociation"
table
="T_User"
>
<
id
name
="UserId"
column
="UserId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="UserName"
type
="String"
name
="UserName"
not-null
="true"
length
="64"
/>
<
property
column
="Password"
type
="String"
name
="Password"
not-null
="true"
length
="32"
/>
<
property
column
="Email"
type
="String"
name
="Email"
length
="64"
/>
<
bag
name
="Roles"
table
="T_User_Role"
lazy
="true"
>
<
key
column
="UserId"
/>
<
many-to-many
class
="DDLLY.TestNHibernate.TestAssociation.ManyToMany.Role,DDLLY.TestNHibernate.TestAssociation"
column
="RoleId"
/>
</
bag
>
</
class
>
</
hibernate-mapping
>
<?
xml version="1.0" encoding="utf-8"
?>
<
hibernate-mapping
xmlns
="urn:nhibernate-mapping-2.0"
>
<
class
name
="DDLLY.TestNHibernate.TestAssociation.ManyToMany.Role,DDLLY.TestNHibernate.TestAssociation"
table
="T_Role"
>
<
id
name
="RoleId"
column
="RoleId"
type
="Int32"
unsaved-value
="0"
>
<
generator
class
="native"
/>
</
id
>
<
property
column
="RoleName"
type
="String"
name
="RoleName"
not-null
="true"
length
="64"
/>
<
bag
name
="Users"
table
="T_User_Role"
lazy
="true"
inverse
="true"
>
<
key
column
="RoleId"
/>
<
many-to-many
class
="DDLLY.TestNHibernate.TestAssociation.ManyToMany.User,DDLLY.TestNHibernate.TestAssociation"
column
="UserId"
/>
</
bag
>
</
class
>
</
hibernate-mapping
>
4.4 说明
many-to-many性能不佳,数据量大时应尽可能避免使用。并尽可能使用lazy="true"。
在数据量少的一端设置inverse="true",让数据量多的一段维护cascade。
二、cascade分析
1.总述
cascade:(默认为none)级联。指明哪些操作会从对象级联到关联的对象。
orphans:孤儿,没有夫对象的子对象。对于代码Child.Parent==null,对于数据库T_Child表中ParentId为Null的数据。
delete orphans表示cascade时删除孤儿。
一般系统中是不允许孤儿存在的,我们可以通过数据库的约束来限制孤儿,例如T_Child的ParentId设为Not NULL。
如果确实存在孤儿请考虑适合的cascade策略。
cascade类型 |
对应操作 |
all |
Save / Delete / Update |
all-delete-orphan |
Save / Delete / Update + delete orphans |
delete-orphan |
Delete + delete orphans |
none |
No Cascades |
delete |
Delete |
save-update |
Save / Update |
2.one-to-one
a.初始化数据
PersonId |
Name |
Job |
1 |
DDL |
编程 |
2 |
LLY |
NULL |
b.测试方法
TestAddPersonWithAddEmployee
Person person
=
new
Person();
person.Name
=
"
newPerson
"
;
Employee employee
=
new
Employee();
employee.Job
=
"
newJob
"
;
person.Employee
=
employee;
employee.Person
=
person;
session.Save(person);
TestUpdatePersonWithAddEmployee
Person person
=
session.Load(
typeof
(Person),
2
)
as
Person;
person.Employee
=
new
Employee();
person.Employee.Person
=
person;
person.Employee.Job
=
"
LLYJob
"
;
session.Update(person);
TestUpdatePersonWithUpdateEmployee
Person person
=
session.Load(
typeof
(Person),
1
)
as
Person;
person.Employee.Job
=
"
DDL'New Job
"
;
session.Update(person);
TestDeletePersonWithDeleteEmployee
Person person
=
session.Load(
typeof
(Person),
1
)
as
Person;
session.Delete(person);
c.测试结果
测试方法 |
save-update |
delete |
delete-orphan |
all |
all-delete-orphan |
none |
TestAddPersonWithAddEmployee |
Y |
N |
N |
Y |
Y |
N |
TestUpdatePersonWithAddEmployee |
Y |
N |
N |
Y |
Y |
N |
TestUpdatePersonWithUpdateEmployee |
Y |
Y |
Y |
Y |
Y |
Y |
TestDeletePersonWithDeleteEmployee |
N |
Y |
Y |
Y |
Y |
N |
2.另一种one-to-one
a.初始化数据
PersonId |
Name |
EmployeeId |
Job |
1 |
DDL |
1 |
编程 |
2 |
LLY |
NULL |
NULL |
b.测试方法
TestAddPersonWithAddEmployee
不支持
TestUpdatePersonWithAddEmployee
Person person
=
session.Load(
typeof
(Person),
2
)
as
Person;
person.Employee
=
new
Employee();
person.Employee.Person
=
person;
person.Employee.Job
=
"
LLYJob
"
;
session.Update(person);
session.Flush();
TestUpdatePersonWithUpdateEmployee
Person person
=
session.Load(
typeof
(Person),
1
)
as
Person;
person.Employee.Job
=
"
DDL'New Job
"
;
session.Update(person);
session.Flush();
TestDeletePersonWithDeleteEmployee
Person person
=
session.Load(
typeof
(Person),
1
)
as
Person;
session.Delete(person);
session.Flush();
c.测试结果
测试方法 |
save-update |
delete |
delete-orphan |
all |
all-delete-orphan |
none |
TestAddPersonWithAddEmployee |
不支持 |
不支持 |
不支持 |
不支持 |
不支持 |
不支持 |
TestUpdatePersonWithAddEmployee |
Y |
N |
N |
Y |
Y |
N |
TestUpdatePersonWithUpdateEmployee |
Y |
Y |
Y |
Y |
Y |
Y |
TestDeletePersonWithDeleteEmployee |
N |
Y |
Y |
Y |
Y |
N |
3.one-to-many(双向)
a.初始化数据
ParentId |
ParentName |
ChildId |
ChildName |
1 |
Parent1 |
1 |
Child1 |
2 |
Parent2 |
NULL |
NULL |
b.测试方法
TestAddParentWithAddChild
Parent parent
=
new
Parent();
parent.Name
=
"
NewParent
"
;
Child child
=
new
Child();
child.Name
=
"
NewChild
"
;
child.Parent
=
parent;
parent.Children.Add(child);
session.Save(parent);
session.Flush();
TestUpdateParentWithAddChild
Parent parent
=
session.Load(
typeof
(Parent),
2
)
as
Parent;
Child child
=
new
Child();
child.Name
=
"
NewChild
"
;
child.Parent
=
parent;
parent.Children.Add(child);
session.Update(parent);
session.Flush();
TestUpdateParentWithUpdateChild
Parent parent
=
session.Load(
typeof
(Parent),
1
)
as
Parent;
Child child
=
(Child) parent.Children[
0
];
child.Name
=
"
UpdateName
"
;
session.Update(parent);
session.Flush();
TestDeleteParentWithChild
Parent parent
=
session.Load(
typeof
(Parent),
1
)
as
Parent;
session.Delete(parent);
session.Flush();
c.测试结果
测试方法 |
save-update |
delete |
delete-orphan |
all |
all-delete-orphan |
none |
TestAddParentWithAddChild |
Y |
N |
N |
Y |
Y |
N |
TestUpdateParentWithAddChild |
Y |
N |
N |
Y |
Y |
N |
TestUpdateParentWithUpdateChild |
Y |
Y |
Y |
Y |
Y |
Y |
TestDeleteParentWithChild |
N |
Y |
Y |
Y |
Y |
N |
4.one-to-many(单向)
a.初始化数据
同上
b.测试方法
TestAddParentWithAddChild
不支持
TestUpdateParentWithAddChild
Parent parent
=
session.Load(
typeof
(Parent),
2
)
as
Parent;
Child child
=
new
Child();
child.Name
=
"
NewChild
"
;
child.ParentId
=
parent.ParentId;
parent.Children.Add(child);
session.Update(parent);
session.Flush();
TestUpdateParentWithUpdateChild
Parent parent
=
session.Load(
typeof
(Parent),
1
)
as
Parent;
Child child
=
(Child) parent.Children[
0
];
child.Name
=
"
UpdateName
"
;
session.Update(parent);
session.Flush();
TestDeleteParentWithChild
Parent parent
=
session.Load(
typeof
(Parent),
1
)
as
Parent;
session.Delete(parent);
session.Flush();
c.测试结果
测试方法 |
save-update |
delete |
delete-orphan |
all |
all-delete-orphan |
none |
TestAddParentWithAddChild |
不支持 |
不支持 |
不支持 |
不支持 |
不支持 |
不支持 |
TestUpdateParentWithAddChild |
Y |
N |
N |
Y |
Y |
N |
TestUpdateParentWithUpdateChild |
Y |
Y |
Y |
Y |
Y |
Y |
TestDeleteParentWithChild |
Parent被删除,Child成为孤儿 |
Y |
Y |
Y |
Y |
Parent被删除,Child成为孤儿 |
5.many-to-many
many-to-many和别的关联映射有所不同。例子中:Role和User没有直接的依赖关系,而是通过一张中间表完成。在删除User时一般不会要求删除Role,而是删除之间的关系(即从中间表删除数据)。
a.初始化数据
UserId |
UserName |
Password |
Email |
RoleId |
RoleName |
1 |
DDL |
1 |
NULL |
1 |
角色1 |
1 |
DDL |
1 |
NULL |
2 |
角色2 |
2 |
LLY |
2 |
NULL |
1 |
角色1 |
3 |
陌生人 |
3 |
NULL |
NULL |
NULL |
NULL |
NULL |
NULL |
NULL |
3 |
角色3 |
b.测试方法
TestAddRoleToUser
User user
=
session.Load(
typeof
(User),
1
)
as
User;
Role role
=
session.Load(
typeof
(Role),
3
)
as
Role;
user.Roles.Add(role);
role.Users.Add(user);
session.Update(user);
session.Flush();
TestRemoveRoleFromUser
User user
=
session.Load(
typeof
(User),
1
)
as
User;
Role role
=
session.Load(
typeof
(Role),
2
)
as
Role;
user.Roles.Remove(role);
role.Users.Remove(user);
session.Update(user);
session.Flush();
TestUpdateUserWithRole
User user
=
session.Load(
typeof
(User),
2
)
as
User;
((Role) user.Roles[
0
]).RoleName
=
"
UpdateRole
"
;
session.Update(user);
session.Flush();
TestDeleteUserWithSetRole
User user
=
session.Load(
typeof
(User),
1
)
as
User;
session.Delete(user);
session.Flush();
c.测试结果
测试方法 |
save-update |
delete |
delete-orphan |
all |
all-delete-orphan |
none |
TestAddRoleToUser |
Y |
Y |
Y |
Y |
Y |
Y |
TestRemoveRoleFromUser |
Y |
Y |
Y |
Y |
Y |
Y |
TestUpdateUserWithRole |
Y |
Y |
Y |
Y |
Y |
Y |
TestDeleteUserWithSetRole |
N |
Uer被删除,但和其有关的Role也被删除 |
Uer被删除,但和其有关的Role也被删除 |
Uer被删除,但和其有关的Role也被删除 |
Uer被删除,但和其有关的Role也被删除 |
N |
三、结论
关联是NHibernate里面功能很强的一块,但也使很容易滥用而造成引起性能或其他问题的地方。所以请慎重的使用。
在使用之前,请考虑好以下问题:
1.关系分析,一对多,多对多,还是一对一。
2.确定依赖关系,例如:Child依赖于Parent。
3.是否允许存在孤儿,例如:存在Child没有Parent(即在数据库中ParentId为Null的Child)。
4.在对等的关系中是否有主动端。例如:需要给Parent设置Child还是给Child找Parent,或者两边都可以操作。
5.关联两端可能出现的数据量以及在页面显示时是否分页。如果数据量大或者页面上需要分页显示,建议不要采用关联映射。如果数据量大,性能会不好,如果需要分页,关联所有数据似乎没有什么意思。
6.页面上可能的对象操作方法。例如:先读取一个Parent,然后添加Child,然后保存。
请根据你的情况设置关联映射,而对于cascade标准的设置可以满足绝大多数的需要,如一有特殊情况,请按照上面的分析选择合适的。
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