Nhibernate producing proxy despite HQL fetch

问题:

I have the following HQL statement:

select distinct t from TaskEntity as 
inner join fetch t.Case as c
inner join fetch c.Client as client 
inner join fetch c.Matter as matter

However, despite Matter having a FETCH against it, it's still returning as a proxy.

My mapping for this object is below

References(x => x.Matter).Columns(new[] {"c_client","c_matter" });

I've tried using JOIN on this, but my issue I'm going from 1 to 2 columns, so it wouldn't accept the mapping.

Any thoughts?

Thanks,

回答1:

Be aware that you must also provide a correct GetHashCode implementation.

Your Equals implementation is also not great.

Furthermore, both methods should return 'static' values. I have not seen your class but is should be something like:

public class TaskEntity
{
    public int AccountNumber { get; protected set; }
    public int CaseNumber { get; protected set; }
    public Client Client { get; set; }
    public Matter Matter { get; set; }

    public TaskEntity(int accountNr, caseNr)
    {
        AccountNumber = accountNr;
        CaseNumber = caseNr;
    }

    protected TaskEntity() {} // Needed for NHibernate proxies
}

I really recommend that you put your component id's in seperate classes when possible.

Furthermore, read the following article about override Equal as your current implementation is probably flawed : http://msdn.microsoft.com/en-us/library/bsc2ak47.aspx especially understand the part regarding inheritance and base types.

回答2:

I worked out the problem that was causing this issue.

It also resolves to Composite IDs!

Earlier in the project Nhibernate was warning that I was not overriding Equals and GetHashCode, to circumvent lots of code changes, and to promote code re-use I made a CompositeBaseEntity class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Case.Infrastructure
{
    public class BaseCompositeEntity : BaseEntity
    {
        public override int GetHashCode()
        {
            return base.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            return base.Equals(obj);
        }
    }
}

This class, puts back in place what Nhibernate was telling me to avoid! As there are two keys to compare equality against, we MUST override the Equals & GetHashCode() methods to become something like:

public override bool Equals(object obj)
        {
            if (obj == null)
                return false;
            var t = obj as ClientMatterEntity;
            if (t == null)
                return false;
            if (AccountNumber== t.ClientAcconuntNumber && CaseNumber == t.CaseNumber)
                return true;
            return false;
        }

This way, Nhibernate knows exactly how comparison should be done, and then knows if it has that object in a first-level cache (which it will, as we specified fetch).

More information can be found here: http://nhforge.org/blogs/nhibernate/archive/2010/07/01/nhibernate-and-composite-keys.aspx