NHibernate级联保存

Question

这是试图将 null 插入 Comment.BlogArticleID。

出现以下 GenericADOException： “无法插入：[NHibernate__OneToMany.BO.Comment][SQL：INSERT INTO Comment (Name) VALUES (?); select SCOPE_IDENTITY()]”

出现以下内部异常： “无法将 NULL 值插入表“Relationships_Test_OneToMany.dbo.Comment”列“BlogArticleID”；列不允许为空值。INSERT 失败。\r\n该语句已终止。”

我需要单向映射。目前提供的答案是关于双向映射。

NHibernate 级联保存是否可以与本机 ID 生成器一起使用？

数据库表：

BlogArticle{ID, Name}，如果是 ID，则 Identity=true。

Comment{ID, Name, BlogArticleID}，如果是 ID，则 Identity=true。

Comment.hbm.xml

<hibernate-mapping
  xmlns="urn:nhibernate-mapping-2.2"
  assembly="NHibernate__OneToMany.BO"
  namespace="NHibernate__OneToMany.BO"
  default-access="property">

  <class name="Comment" table="Comment">
    <id name="ID">
      <generator class="native" />
    </id>

    <property name="Name" />
  </class>
</hibernate-mapping>

public class Comment
    {
        private int _id;
        public virtual int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        public Comment()
        {
        }

        public Comment(string name)
        {
            this._name = name;
        }

        private string _name;
        public virtual string Name
        {
            get { return _name; }
            set { _name = value; }
        }   
    }

BlogArticle.hbm.xml

<hibernate-mapping 
  xmlns="urn:nhibernate-mapping-2.2"
  namespace="NHibernate__OneToMany.BO"
  assembly="NHibernate__OneToMany.BO"
  default-access="property">
  <class name="BlogArticle"  table="BlogArticle">
    <id name="ID">
      <generator class="native" />
    </id>

    <property name="Name" column="Name" />

    <bag name="Comments" cascade="all" >
      <key column="BlogArticleID" />
      <one-to-many class="Comment" />
    </bag>
  </class>
</hibernate-mapping>


public class BlogArticle
    {
        private int _id;
        public virtual int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        private string _name;
        public virtual string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        private IList _depts;
        public virtual IList Comments
        {
            get { return _depts; }
            set { _depts = value; }
        }   
    }

主

class Program
{
    static void Main(string[] args)
    {
        BlogArticle ba = new BlogArticle();
        ba.Name = "Humanity";
        ba.Comments = new List<Comment>();
        ba.Comments.Add(new Comment("Comm1"));
        ba.Comments.Add(new Comment("Comm2"));
        ba.Comments.Add(new Comment("Comm3"));

        Repository<BlogArticle> rep = new Repository<BlogArticle>();
        rep.Save(ba);
    }
}

存储库

public class Repository<T> : IRepository<T>
    {
        ISession _session;

        public Repository()
        {
            _session = SessionFactoryManager.SessionFactory.OpenSession();
        }

        private void Commit()
        {
            if (_session.Transaction.IsActive)
            {
                _session.Transaction.Commit();
            }
        }

        private void Rollback()
        {
            if (_session.Transaction.IsActive)
            {
                _session.Transaction.Rollback();
                //_session.Clear();
            }
        }

        private void BeginTransaction()
        {
            _session.BeginTransaction();
        }

        public void Save(T obj)
        {
            try
            {
                this.BeginTransaction();

                _session.Save(obj);                

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }            
        }

        void IRepository<T>.Save(IList<T> objs)
        {
            try
            {
                this.BeginTransaction();

                for (Int32 I = 0; I < objs.Count; ++I)
                {
                    _session.Save(objs[I]);
                }

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }
        }

        void IRepository<T>.Update(T obj)
        {
            try
            {
                this.BeginTransaction();

                _session.Update(obj);

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }
        }

        void IRepository<T>.Update(IList<T> objs)
        {
            try
            {
                this.BeginTransaction();

                for (Int32 I = 0; I < objs.Count; ++I)
                {
                    _session.Update(objs[I]);
                }

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }
        }

        void IRepository<T>.Delete(T obj)
        {
            try
            {
                this.BeginTransaction();

                _session.Delete(obj);

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }  
        }

        void IRepository<T>.Delete(IList<T> objs)
        {
            try
            {
                this.BeginTransaction();

                for (Int32 I = 0; I < objs.Count; ++I)
                {
                    _session.Delete(objs[I]);
                }

                this.Commit();
            }
            catch (Exception ex)
            {
                this.Rollback();

                throw ex;
            }
        }

        T IRepository<T>.Load<T>(object id)
        {
            return _session.Load<T>(id);
        }

        public IList<T> Get<T>(int pageIndex, int pageSize)
        {
            ICriteria criteria = _session.CreateCriteria(typeof(T));
            criteria.SetFirstResult(pageIndex * pageSize);
            if (pageSize > 0)
            {
                criteria.SetMaxResults(pageSize);
            }
            return criteria.List<T>();
        }

        public T Get<T>(object id)
        {
            return _session.Get<T>(id);
        }

        public IList<T> Get<T>()
        {
            return Get<T>(0, 0);
        }

        public IList<T> Get<T>(string propertyName, bool Ascending)
        {
            Order cr1 = new Order(propertyName, Ascending);

            IList<T> objsResult = _session.CreateCriteria(typeof(T)).AddOrder(cr1).List<T>();

            return objsResult;
        }

        public IList<T> Find<T>(IList<string> strs)
        {
            System.Collections.Generic.IList<NHibernate.Criterion.ICriterion> objs = new System.Collections.Generic.List<ICriterion>();
            foreach (string s in strs)
            {
                NHibernate.Criterion.ICriterion cr1 = NHibernate.Criterion.Expression.Sql(s);
                objs.Add(cr1);
            }
            ICriteria criteria = _session.CreateCriteria(typeof(T));
            foreach (ICriterion rest in objs)
                _session.CreateCriteria(typeof(T)).Add(rest);

            criteria.SetFirstResult(0);
            return criteria.List<T>();
        }

        public void Detach(T item)
        {
            _session.Evict(item);
        }        
    }

Answer 1

关联类的键列 (Comment.BlogArticleID) 在数据库中必须可为空。 NHibernate 将插入行并使该列保留为 NULL，然后执行更新以设置键。

将 not-null="true" 添加到关键元素将不起作用，因为此属性仅由架构导出工具使用。

请注意，失败的插入包括对新子行生成的标识的选择。

Answer 2

您尚未将文章映射到评论：

<hibernate-mapping
  xmlns="urn:nhibernate-mapping-2.2"
  assembly="NHibernate__OneToMany.BO"
  namespace="NHibernate__OneToMany.BO"
  default-access="property">

  <class name="Comment" table="Comment">
    <id name="ID">
      <generator class="native" />
    </id>

    <property name="Name" />
    <many-to-one name="BlogArticle" column="BlogArticleID" />   <----------
  </class>
</hibernate-mapping>

public class Comment
    {
        private int _id;
        public virtual int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        public Comment() { }

        public Comment(int id, string name, BlogArticle article) <------------
        {
            this._id = id;
            this._name = name;
            this._blogArticle = article; <------------
        }

        private string _name;
        public virtual string Name
        {
            get { return _name; }
            set { _name = value; }
        }   

        private BlogArticle _blogArticle;       <------------
        public virtual BlogArticle Name       <------------
        {
            get { return _blogArticle; }       <------------
            set { _blogArticle= value; }       <------------
        }   

    }