1.     学习目的:

通过进一步学习nhibernate基础知识，在实现单表CRUD的基础上，实现两表之间one-to-many的关系.

2.     开发环境+必要准备

开发环境: windows 2003,Visual studio .Net 2005,Sql server 2005 developer edition

必要准备: 学习上篇文章单表操作   

3． 对上篇文章中部分解释

 1）在User.hbm.xml中class节点中有一个lazy的属性，这个属性用于指定是否需要延迟加载（lazy loading），在官方文档中称为:lazy fecting.可以说延迟加载是nhibernate最好的特点，因为它可以在父类中透明的加载子类集合，这对于many-to-one的业务逻辑中，真是方便极了。但是有些时候，父类是不需要携带子类信息的。这时候如果也加载，无疑对性能是一种损失。在映射文件的class节点中可以通过配置lazy属性来指定是否支持延迟加载，这就更灵活多了。 

 2) 在User.hbm.xml中generate节点，代表的是主键的生成方式，上个例子中的”native”根据底层数据库的能力选择identity,hilo,sequence中的一个，比如在MS Sql中，使我们最经常使用的自动增长字段，每次加1. 

3) 在NHibernateHelper.cs中，创建Configuration对象的代码：new Configuration().Configure(@"E:\myproject\nhibernatestudy\simle1\NHibernateStudy1\NhibernateSample1\hibernate.cfg.xml")；因为我是在单元测试中调试，所以将绝对路径的配置文件传递给构造函数。如果在windows app或者web app可以不用传递该参数。 

4． 实现步骤

 1）确定实现的业务需求：用户工资管理系统

 2) 打开上篇文章中的NHibernateStudy1解决方案。向项目NhibernateSample1添加类Salary;代码如下

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

namespace NhibernateSample1
{
    public partial class Salary
    {
        int _id;
        User _user;
        int _year;
        int _month;
        int _envy;
        decimal _money;
        /// <summary>
        /// 工资编号
        /// </summary>
        public virtual int Id
        {
            get
            {
                return _id;
            }
            set
            {
                _id = value;
            }
        }
        /// <summary>
        /// 雇员
        /// </summary>
        public virtual User Employee
        {
            get
            {
                return _user;
            }
            set
            {
                _user = value;
            }
        }
        /// <summary>
        /// 年度
        /// </summary>
        public int Year
        {
            get
            {
                return _year;
            }
            set
            {
                _year = value;
            }
        }
        /// <summary>
        /// 月份
        /// </summary>
        public int Month
        {
            get
            {
                return _month;
            }
            set
            {
                _month = value;
            }
        }
        /// <summary>
        /// 季度
        /// </summary>
        public int Envy
        {
            get
            {
                return _envy;
            }
            set
            {
                _envy = value;
            }
        }
        /// <summary>
        /// 工资
        /// </summary>
        public decimal Money
        {
            get
            {
                return _money;
            }
            set
            {
                _money = value;
            }
        }
    }
}

3) 更改User.cs,在User里面添加SalaryList属性：

 1private System.Collections.IList _salaryList;
 2 /// <summary>
 3        /// 工资列表
 4        /// </summary>
 5        public System.Collections.IList SalaryList
 6        {
 7            get
 8            {
 9                return _salaryList;
10            }
11            set
12            {
13                _salaryList = value;
14            }
15        }

4）修改User.hbm.xml，加入bag节点

<bag name="SalaryList" table="Salary" inverse="true" lazy="true" cascade="all">
      <key column="Id"/>
      <one-to-many class="NhibernateSample1.Salary,NhibernateSample1"></one-to-many>
    </bag>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="NhibernateSample1.Salary,NhibernateSample1" table="Salary" lazy="false">
    <id name="Id" column="Id" unsaved-value="0">
      <generator class="native" />
    </id>
    <property name="Year" column="Year" type="Int32" not-null="true"></property>
    <property name="Month"  column="Month"  type="Int32" not-null="true"></property>
    <property name="Envy"  column="Envy"  type="Int32" not-null="true"></property>
    <property name="Money"  column="Money"  type="Decimal" not-null="true"></property>
    <many-to-one name="Employee" column="Uid" not-null="true"></many-to-one>
  </class>
</hibernate-mapping>

6）编写CRUD类

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using NHibernate;
using NHibernate.Cfg;
using NHibernate.Tool.hbm2ddl;

namespace NhibernateSample1
{
    public  class UserSalaryFixure
    {
        private ISessionFactory _sessions; 
        public void Configure()
        {
            Configuration cfg = GetConfiguration();      
            _sessions = cfg.BuildSessionFactory();
        }
        Configuration GetConfiguration()
        {
            string cfgPath = @"E:\my project\nhibernate study\simle 1\NHibernateStudy1\NhibernateSample1\hibernate.cfg.xml";
            Configuration cfg = new Configuration().Configure(cfgPath);
            return cfg;
        }
        public void ExportTables()
        {
            Configuration cfg = GetConfiguration();           
            new SchemaExport(cfg).Create(true, true);
        }
        public User CreateUser(String name,string pwd)
        {
            User u = new User();
            u.Name = name;
            u.Pwd = pwd;
            u.SalaryList = new ArrayList();

            ISession session = _sessions.OpenSession();

            ITransaction tx = null;

            try
            {
                tx = session.BeginTransaction();
                session.Save(u);
                tx.Commit();
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                throw e;
            }
            finally
            {
                session.Close();
            }

            return u;
        }
        public Salary CreateSalary(User u, int year,int month,int envy,decimal money)
        {
            Salary item = new Salary();
            item.Year = year;
            item.Money = money;
            item.Envy = envy;
            item.Month = month;
            item.Employee = u;
            u.SalaryList.Add(item);
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;

            try
            {
                tx = session.BeginTransaction();
                session.Update(u);
                tx.Commit();
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                throw e;
            }
            finally
            {
                session.Close();
            }
            return item;
        }
        public Salary CreateSalary(int uid,int year, int month, int envy, decimal money)
        {
            Salary item = new Salary();
            item.Year = year;
            item.Money = money;
            item.Envy = envy;
            item.Month = month;
            
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;
            try
            {
                tx = session.BeginTransaction();
                User u = (User)session.Load(typeof(User), uid);
                item.Employee = u;
                u.SalaryList.Add(item);
                tx.Commit();
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                throw e;
            }
            finally
            {
                session.Close();
            }
            return item;
        }
        public Salary GetSalary(int salaryID)
        {
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;
            try
            {
                tx = session.BeginTransaction();
                Salary item = (Salary)session.Load(typeof(Salary),
                    salaryID);               
                tx.Commit();
                return item;
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                return null;
            }
            finally
            {
                session.Close();
            }
            return null;
        }
        public User GetUser(int uid)
        {
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;
            try
            {
                tx = session.BeginTransaction();
                User item = (User)session.Load(typeof(User),
                    uid);
                tx.Commit();
                return item;
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                return null;
            }
            finally
            {
                session.Close();
            }
            return null;
        }
        public void UpdateSalary(int salaryID, decimal money)
        {
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;
            try
            {
                tx = session.BeginTransaction();
                Salary item = (Salary)session.Load(typeof(Salary),
                    salaryID);
                item.Money = money;
                tx.Commit();
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                throw e;
            }
            finally
            {
                session.Close();
            }
        }

        public void Delete(int uid)
        {
            ISession session = _sessions.OpenSession();
            ITransaction tx = null;
            try
            {
                tx = session.BeginTransaction();
                Salary item = session.Load(typeof(Salary), uid) as Salary; ;
                session.Delete(item);
                tx.Commit();
            }
            catch (HibernateException e)
            {
                if (tx != null) tx.Rollback();
                throw e;
            }
            finally
            {
                session.Close();
            }
        }

    }
}