问题
Using nHibernate 3.2, C# 4.0, SQL Server 2008 R2 Express
I have two business entities - Broker and Market. They are stored in the brokers and markets tables respectively. I also have brokerMarkets table with one extra column called MinIncrement. There's a many-many relationship between Broker and Market, but only when I want to store a MinIncrement value (i.e. it's optional). My classes look like this:
public class Market : BusinessBase
{
public Market() {}
public virtual int Id { get; set; }
public virtual string Symbol { get; set; }
public virtual string Description { get; set; }
}
public class Broker : BusinessBase
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual bool IsDefault { get; set; }
public virtual bool IsActive { get; set; }
public virtual ISet<Account> Accounts { get; set; }
}
public class BrokerMarket : Market
{
public BrokerMarket() { }
public virtual Broker Broker {get; set;}
public virtual decimal MinIncrement { get; set; }
}
My mapping files look like this: Market.hbm.xml
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="MooDB"
namespace="MooDB.BusinessLayer">
<class name="MooDB.BusinessLayer.Market,MooDB" table="markets">
<id name="Id" column="marketId" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<version name="Version" column="version" type="integer" unsaved-value="0" />
<property name="Symbol" column="symbol" type="String" length="10" not-null="true" />
<property name="Description" column="description" type="String" length="30" not-null="true" />
<set name="Brokers" generic="true" table="brokerMarkets">
<key column="marketId" />
<many-to-many column="brokerId" class="MooDB.BusinessLayer.Broker,MooDB" />
</set>
</class>
</hibernate-mapping>
Broker.hbm.xml
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="MooDB"
namespace="MooDB.BusinessLayer">
<class name="MooDB.BusinessLayer.Broker,MooDB" table="brokers">
<id name="Id" column="brokerId" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<version name="Version" column="version" type="integer" unsaved-value="0" />
<property name="Name" column="broker" type="String" length="50" not-null="true" />
<property name="IsActive" column="isActive" type="bool" not-null="true" />
<property name="IsDefault" column="isDefault" type="bool" not-null="true" />
<set name="Markets" generic="true" table="brokerMarkets">
<key column="brokerId" />
<many-to-many column="marketId" class="MooDB.BusinessLayer.Market,MooDB" />
</set>
<set name="Accounts" table="accounts" generic="true" inverse="true">
<key column="brokerId" />
<one-to-many class="MooDB.BusinessLayer.Account,MooDB" />
</set>
</class>
</hibernate-mapping>
In my data access layer I have a method to add a BrokerMarket:
public void AddBrokerMarket(BrokerMarket bm)
{
using (ITransaction tx = _session.BeginTransaction())
{
try
{
_session.Save(bm);
_session.Flush();
tx.Commit();
}
catch (HibernateException)
{
tx.Rollback();
throw;
}
}
}
In my unit test I try and add a BrokerMarket like this:
[Test]
public void CanAddBrokerMarket()
{
Broker broker = _provider.GetBrokerById(1);
Market market = _provider.GetMarketById(2);
var brokerMarket = new BrokerMarket { Broker = broker, Description = market.Description, Symbol = market.Symbol, MinIncrement = 0.01M };
_provider.AddBrokerMarket(brokerMarket);
}
When I run the test I get this error:
Running the tests. Test 'MooDBTests/MooDB/Tests/DataLayerTests/CanAddBrokerMarket' failed: Message NHibernate.MappingException : No persister for: MooDB.BusinessLayer.BrokerMarket Stack Trace at NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName) at NHibernate.Impl.SessionImpl.GetEntityPersister(String entityName, Object obj) at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.FireSave(SaveOrUpdateEvent event) at NHibernate.Impl.SessionImpl.Save(Object obj) NHibernateDataProvider.cs(91,0): at MooDB.DataLayer.NHibernateDataProvider.AddBrokerMarket(BrokerMarket bm) DataLayerTests.cs(81,0): at MooDB.Tests.DataLayerTests.CanAddBrokerMarket()
I'm not sure what I've done wrong. Do I need to add a Broker collection in the Market class and a Market collection in the Broker class? I did try that but I get the same error, and I think I'm missing something conceptually somewhere.
UPDATE
I have implemented the following changes: Market.hbm.xml
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="MooDB"
namespace="MooDB.BusinessLayer">
<class name="MooDB.BusinessLayer.Market,MooDB" table="markets">
<id name="Id" column="marketId" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<version name="Version" column="version" type="integer" unsaved-value="0" />
<property name="Symbol" column="symbol" type="String" length="10" not-null="true" />
<property name="Description" column="description" type="String" length="30" not-null="true" />
<map name="BrokerMarkets" table="brokerMarkets" lazy="true" cascade="none">
<cache usage="read-write"/>
<key column="marketId" />
<index column="brokerId" type="Int32" />
<composite-element class="MooDB.BusinessLayer.BrokerMarket,MooDB">
<parent name="Market"/>
<property name="MinIncrement" column="minIncrement" type="decimal" />
<many-to-one name="Broker" class="MooDB.BusinessLayer.Broker,MooDB" column="brokerId" />
</composite-element>
</map>
</class>
</hibernate-mapping>
Broker.hbm.xml
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="MooDB"
namespace="MooDB.BusinessLayer">
<class name="MooDB.BusinessLayer.Broker,MooDB" table="brokers">
<id name="Id" column="brokerId" type="Int32" unsaved-value="0">
<generator class="native" />
</id>
<version name="Version" column="version" type="integer" unsaved-value="0" />
<property name="Name" column="broker" type="String" length="50" not-null="true" />
<property name="IsActive" column="isActive" type="bool" not-null="true" />
<property name="IsDefault" column="isDefault" type="bool" not-null="true" />
<set name="Accounts" table="accounts" generic="true" inverse="true">
<key column="brokerId" />
<one-to-many class="MooDB.BusinessLayer.Account,MooDB" />
</set>
</class>
</hibernate-mapping>
Market class:
public class Market : BusinessBase
{
public Market() {}
public virtual int Id { get; set; }
public virtual string Symbol { get; set; }
public virtual string Description { get; set; }
public virtual ISet<BrokerMarket> BrokerMarkets { get; set; } //added this line
}
BrokerMarket class
public class BrokerMarket : Market
{
public BrokerMarket() { }
public virtual Broker Broker {get; set;}
public virtual Market Market { get; set; } // added this line
public virtual decimal MinIncrement { get; set; }
}
Everything else is unchanged. I run the unit test again and I get:
Running the tests. Test 'MooDBTests/MooDB/Tests/DataLayerTests/CanAddBrokerMarket' failed: Message TestFixtureSetUp failed in DataLayerTests
Test 'MooDBTests/MooDB/Tests/DataLayerTests' failed: Message SetUp : NHibernate.MappingException : Repeated column in mapping for collection: MooDB.BusinessLayer.Market.BrokerMarkets column: brokerId
UPDATE 2
If I remove
<index column="brokerId" type="Int32" />
from Market.hbm.xml I get this error when running the unit test:
Running the tests. Test 'MooDBTests/MooDB/Tests/DataLayerTests/CanAddBrokerMarket' failed: Message TestFixtureSetUp failed in DataLayerTests
Test 'MooDBTests/MooDB/Tests/DataLayerTests' failed: Message SetUp : NHibernate.MappingException : MooDB.Mappings.Market.hbm.xml(17,10): XML validation error: The element 'map' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'composite-element' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'map-key, composite-map-key, map-key-many-to-many, index, composite-index, index-many-to-many, index-many-to-any' in namespace 'urn:nhibernate-mapping-2.2'. ----> System.Xml.Schema.XmlSchemaValidationException : The element 'map' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'composite-element' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'map-key, composite-map-key, map-key-many-to-many, index, composite-index, index-many-to-many, index-many-to-any' in namespace 'urn:nhibernate-mapping-2.2'.
回答1:
the error could be because you have not defined mapping for BrokerMarket Class, If you want to save broker market like the way you are doin will have to create BrokerMarket.hbm.xml. you may also have a look at using composite element here something like http://thesoftwaresimpleton.blogspot.com/2010/03/nhibernate-many-to-many-with-extra.html
来源：https://stackoverflow.com/questions/8766096/how-to-configure-nhibernate-for-many-many-mapping