NHibernate：延迟加载IUserType [英] NHibernate: Lazy loading of IUserType

问题描述

假设我们有一个存储客户细节的系统和一个存储雇员细节的系统（假设情况！）。当EmployeeSystem访问一个Employee时，客户端信息可以通过使用WCF的ClientSystem访问，实现在IUserType中：

 < hibernate-mapping xmlns =urn：nhibernate-mapping-2.2
 assembly =EmployeeSystemnamespace =EmployeeSystem.Entities> 
< class name =Employeetable =`Employee`> 
< id name =Idcolumn =`Id`type =long> 
< generator class =native/> 
< / id> 
< property name =Name/> 
< property 
 name =Clientcolumn =`ClientId`
 lazy =true
 type =EmployeeSystem.UserTypes.ClientUserType，EmployeeSystem/> 
< / class> 
< / hibernate-mapping> 
  

IUserType实现：

  public class ClientUserType：IUserType 
 {
 ... 
 
 public object NullSafeGet（IDataReader rs，string [] names，object owner）
 {
 object obj = NHibernateUtil.Int32.NullSafeGet（rs，names [0]）; 
 
 IClientService clientService = new ClientServiceClient（）; 
 ClientDto clientDto = null; 
 
 if（null！= obj）
 {
 clientDto = clientService.GetClientById（Convert.ToInt64（obj））; 
} 
 
客户端客户端=新客户端
 {
 Id = clientDto.Id，
名称= clientDto.Name 
}; 
 
返回客户端; 
} 
 
 ... 
 
} 
  

即使我在属性上有lazy =true，只要加载Employee，它就会加载客户端。这是正确的行为？我是否必须在NullSafeGet中自己实现惰性加载，或者我是否缺少某些内容？

解决方案

它是一对一关系。由于hibernate文档表明这是完全可能的，甚至似乎在xml配置文件中有一些选项可用于切换一对一关系的延迟加载，但它们显然不起作用。

一对一懒惰关联

Say we have a system that stores details of clients, and a system that stores details of employees (hypothetical situation!). When the EmployeeSystem access an Employee, the Client information is accessed from the ClientSystem using WCF, implemented in an IUserType:

NHibernate mapping:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
    assembly="EmployeeSystem" namespace="EmployeeSystem.Entities">
   <class name="Employee" table="`Employee`"  >
      <id name="Id" column="`Id`" type="long">
         <generator class="native" />
      </id>
      <property name="Name"/>
      <property 
         name="Client" column="`ClientId`"
         lazy="true"
         type="EmployeeSystem.UserTypes.ClientUserType, EmployeeSystem" /> 
   </class>
</hibernate-mapping>

IUserType implementation:

public class ClientUserType : IUserType
{
    ...

    public object NullSafeGet(IDataReader rs, string[] names, object owner)
    {
        object obj = NHibernateUtil.Int32.NullSafeGet(rs, names[0]);

        IClientService clientService = new ClientServiceClient();
        ClientDto clientDto = null;

        if (null != obj)
        {
            clientDto = clientService.GetClientById(Convert.ToInt64(obj));
        }

        Client client = new Client
        {
            Id = clientDto.Id,
            Name = clientDto.Name
        };

        return client;
    }

    ...

}

Even though I have lazy="true" on the property, it loads the Client as soon as the Employee is loaded. Is this correct behaviour? Do I have to implement the lazy loading myself in NullSafeGet or am I missing something?

解决方案

Is it a one-to-one relation. As hibernate documentation suggests that this is all possible, there even appears to be options in the xml configuration file to switch on lazy loading for one-to-one relationships, but they have apparently no effect.

one-to-one lazy association

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