NHibernate 多表查询解决

代码

在项目中应用NHibernate架构时,会经常遇到多表查询,使用select  new  ObjectEntity这种语法,根据查询的内容自己构建相应的实体类.
这是一个小型家庭办公中的实例。有员工表Employee，姓名表Project，工作记录表EmpWorkRecord。一个员工有多条工作记录，工作记录与项目有关。
Employee实体类与映射文件如下。
     public   class  Employee
    {
         private  IList emprecord;

         public  Employee()
        {
            emprecord  =   new  ArrayList();
        }
         private   int  id;

         public   virtual   int  Id
        {
             get  {  return  id; }
             set  { id  =  value; }
        }
         ///   <summary>
         ///  员工姓名
         ///   </summary>
         private    string  empname  =   "" ;

         public   virtual   string  EmpName
        {
             get  {  return  empname; }
             set  { empname  =  value; }
        }
         ///   <summary>
         ///  性别
         ///   </summary>
         private   string  sex  =   "" ;

         public   virtual   string  Sex
        {
             get  {  return  sex; }
             set  { sex  =  value; }
        }
         ///   <summary>
         ///  地址
         ///   </summary>
         private   string  address  =   "" ;

         public   virtual   string  Address
        {
             get  {  return  address; }
             set  { address  =  value; }
        }
         ///   <summary>
         ///  家庭电话
         ///   </summary>
         private   string  housephone  =   "" ;

         public   virtual   string  Housephone
        {
             get  {  return  housephone; }
             set  { housephone  =  value; }
        }
         ///   <summary>
         ///  手机号码
         ///   </summary>
         private   string  telephone  =   "" ;

         public   virtual   string  Telephone
        {
             get  {  return  telephone; }
             set  { telephone  =  value; }
        }
         ///   <summary>
         ///  电子邮件
         ///   </summary>
         private   string  email  =   "" ;
         public   virtual   string  Email
        {
             get  {  return  email; }
             set  { email  =  value; }
        }

         public   virtual  IList EmpRecord
        {
             get  {  return  emprecord; }
             set  { emprecord  =  value; }
        }
         private   IList < EmpGetMonyRecord >  empgetmonyrecord;

         public   virtual  IList < EmpGetMonyRecord >  EmpGetMonyRecord
        {
             get  {  return  empgetmonyrecord; }
             set  { empgetmonyrecord  =  value; }
        }

    }
Employee.hbm.xml文件：
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<? xml version = " 1.0 "  encoding = " utf-8 "   ?>
< hibernate - mapping xmlns = " urn:nhibernate-mapping-2.2 " >
   < class  name = " Finance.Model.Employee,Finance.Model "  table = " Employee " >
     < id name = " Id "  type = " Int32 " >
       < generator  class = " identity " />
     </ id >
     < property name = " EmpName "  type = " String "  length = " 16 "    />
     < property name = " Address "  type = " String "  length = " 100 " />
     < property name = " Sex "  type = " String "  length = " 2 " />
     < property name = " Housephone "  type = " String "  length = " 13 " />
     < property name = " Telephone "  type = " String "  length = " 12 " />
     < property name = " Email "  type = " String "  length = " 50 "   />
     < bag name = " EmpRecord "  table = " EmpWorkRecord "    >
       < key column = " EmpId " ></ key >
       < one - to - many  class = " Finance.Model.EmpWorkRecord,Finance.Model " />
     </ bag >
     < bag name = " EmpGetMonyRecord "  table = " EmpGetMonyRecord "     >
       < key column = " EmpId " ></ key >
       < one - to - many  class = " Finance.Model.EmpGetMonyRecord,Finance.Model " />
     </ bag >
   </ class >
</ hibernate - mapping >
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工作记录实体类EmpWorkRecord以及hbm.xml文件如下：
    public    class  EmpWorkRecord
    {

         private  Employee emp;
         private   int  id;
         private   int  empid;
         private   decimal  wage;
         private  DateTime workdate;
         private   string  worktype;
         private  Project project;

         public  EmpWorkRecord()
        {
            emp  =   new  Employee();
            project  =   new  Project();
        }   
       
         public   virtual   int  Id
        {
             get  {  return  id; }
             set  { id  =  value; }
        }
       

         public   virtual   int  EmpId
        {
             get  {  return  empid; }
             set  { empid  =  value; }
        }
       

         public   virtual   decimal  Wage
        {
             get  {  return  wage; }
             set  { wage  =  value; }
        }
       

         public   virtual  DateTime WorkDate
        {
             get  {  return  workdate; }
             set  { workdate  =  value; }
        }

         public   virtual   string  WorkType
        {
             get  {  return  worktype; }
             set  { worktype  =  value; }
        }
         public   virtual  Project Project
        {
             get  {  return  project; }
             set  { project  =  value; }
        }
         public   virtual  Employee Emp
        {
             get  {  return  emp; }
             set  { emp  =  value; }
        }
    }
－－－EmpWorkRecord.hbm.xml文件－－－－－－－－－－－－－－－－－－－－－－
<? xml version = " 1.0 "  encoding = " utf-8 "   ?>
< hibernate - mapping xmlns = " urn:nhibernate-mapping-2.2 " >
   < import  class = " Finance.Model.EmpWorkJoinEmpProject,Finance.Model " /> // 引入构造实体类EmpWorkJoinEmpProject
   < class  name = " Finance.Model.EmpWorkRecord,Finance.Model "  table = " EmpWorkRecord "   >
     < id name = " Id "  type = " Int32 " >
       < generator  class = " identity " />
     </ id >
     < property name = " Wage "   type = " Decimal "    />
     < property name = " WorkDate "  type = " DateTime "   />
     < property name = " WorkType "  type = " String "  length = " 10 "   ></ property >
     < many - to - one name = " Emp "  column = " EmpId "   class = " Finance.Model.Employee,Finance.Model "  lazy = " false " ></ many - to - one >
     < many - to - one name = " Project "  column = " ProjectId "   class = " Finance.Model.Project,Finance.Model "  lazy = " false " ></ many - to - one >
   </ class >
</ hibernate - mapping >
现在要获取员工的工作记录信息以表的形式显示出来或者绑定GridView上：员工名（EmpName），工作日期（WorkDate），工作类型（WorkType），姓名名称（ProjectName）。如果就做关联查询的结果并不能显示出表的形式，必须把查询出的数据进行处理。
（ 1 ）一种方法是把查询的结果循环遍历构造出表的形式再绑定到gridview。
        // 获取数据
        public  IList GetPage( int  pageIndex,  int  pageSize,  string   where ,  string  orderBy)
        { 
             string  hql  =   " select  m.Name,m.Type,m.Price,cost.Num,cost.PurchaseTime,cost.PurchasePeople,cost.Id from Material m             join m.MaterialCost cost " ;
             return  control.GetManyTablePage(hql,  where , orderBy, pageIndex, pageSize,  " Finance.Model.MaterialCost " );
        }
        // 绑定GridView
         private   void  BindGv()
        {
             string   where   =   null ;
             if  ( this .txtMaterialName.Text.Trim().Length  >   0 )
            {
                 where   =   " Name=' "   +   this .txtMaterialName.Text.Trim()  +   " ' " ;
            }
             int  pageIndex  =  Finance.StringHandling.Integer.GetInteger(Request.QueryString[ " Page " ],  1 );
            IList list  =  materalcostbll.GetPage(pageIndex,  15 ,  where ,  " cost.Id desc " ); 
            List < MaterialJoinCost >  materialjoincost  =   new  List < MaterialJoinCost > ();
            MaterialJoinCost m  =   null ;
            IEnumerator e  =  list.GetEnumerator();
             while  (e.MoveNext())
            {    // 给查询出来的每行赋值
                m  =   new  MaterialJoinCost();
                 object [] obj  =  ( object [])e.Current;
                m.Name  =  obj[ 0 ].ToString();
                m.Price  =   decimal .Parse(obj[ 2 ].ToString());
                m.Num  =  Convert.ToInt32(obj[ 3 ].ToString());
                m.PurchaseTime  =  Convert.ToDateTime(obj[ 4 ].ToString());
                m.PurchasePeople  =  obj[ 5 ].ToString();
                m.Id  =   int .Parse(obj[ 6 ].ToString());
                materialjoincost.Add(m);
            }

            GridView1.DataSource  =  materialjoincost; 
            GridView1.DataBind();
            pageset.Text  =  materalcostbll.GetPageSet(pageIndex,  15 ,  where ,  " MaterialCost.aspx?Page=$ " ,  2 );
        }

（ 2 ）运用NHIbernate查询语法：select  new  EmpWorkJoinEmpProject(...)。
 这里主要介绍方法二，这种方法也是比较常用的方式。
 首先构造EmpWorkJoinEmpProject实体。在EmpWorkRecord.hbm.xml中加上
< import  class = " Finance.Model.EmpWorkJoinEmpProject,Finance.Model " /> 语句，为了是构造实体类时找到该类。
  public   class  EmpWorkJoinEmpProject
    {
         private   int  id;
         private   int  empId;
         private   string  empName;

       
         private   decimal  wage;

         private  DateTime workDate;

       
         private   string  pname;
         private   string  worktype;

         public   string  WorkType
        {
             get  {  return  worktype; }
             set  { worktype  =  value; }
        }
       
         public  EmpWorkJoinEmpProject( int  id,  int  empid,  string  empName,  decimal  wage, string  worktype, DateTime workDate,  string  pname)
        {
             this .id  =  id;
             this .empId  =  empid;
             this .empName  =  empName;
             this .wage  =  wage;
             this .workDate  =  workDate;
             this .pname  =  pname;
             this .worktype  =  worktype;
        }
         public   int  Id
        {
             get  {  return  id; }
             set  { id  =  value; }
        }
         public   int  EmpId
        {
             get  {  return  empId; }
             set  { empId  =  value; }
        }
         public   string  EmpName
        {
             get  {  return  empName; }
             set  { empName  =  value; }
        }

         public   decimal  Wage
        {
             get  {  return  wage; }
             set  { wage  =  value; }
        }
         public  DateTime WorkDate
        {
             get  {  return  workDate; }
             set  { workDate  =  value; }
        }
         public   string  PName
        {
             get  {  return  pname; }
             set  { pname  =  value; }
        }

    }
        1 )获取数据DAL
        public  IList GetDataByQuery( string   where )
       {
             string  hql  = "  select new EmpWorkJoinEmpProject(work.Id, emp.Id,emp.EmpName,work.Wage,work.WorkType,work.WorkDate,p.ProjectName) from EmpWorkRecord work join work.Emp emp,work.Project p " ;
             if  ( ! string .IsNullOrEmpty( where )  &&   where   !=   "" )
            {
                hql +=   "  where  "   +   where ;
            }
             return  control.GetDataByQuery(hql);
        
        }
        2 )EmpWorkRecordBLL代码：
        public  IList GetDataByQuery( string   where )
        {
             return  dal.GetDataByQuery( where );
        }

       3 )绑定GridView
        private   void  BindGv()
        {
             string   where   =   null ;
             if  ( this .txtGemoneyPerson.Text.Trim().Length  >   0 )
            {
                 where   =   " EmpName=' "   +   this .txtGemoneyPerson.Text.Trim()  +   " ' " ;
            }
             int  pageIndex  =  Finance.StringHandling.Integer.GetInteger(Request.QueryString[ " Page " ],  1 );
            IList list  =  workbll.GetPage(pageIndex,  15 ,  where ,  " work.Id desc " ); 
           
            GridView1.DataSource  =  list; 
            GridView1.DataBind();
            pageset.Text  =  workbll.GetPageSet(pageIndex,  15 ,  where ,  " EmpWorkRecordInfo.aspx?Page=$ " ,  2 );  
          
        }