NHibernate初学三之条件查询(Criteria Queries)与AspNetPager分页实例
NHibernate除了SQL与HQL两种查询操作外,还有一种就是条件查询Criteria,本文将从网上整理一些Criteria的理论及小实例,最后通过一个结合AspNetPager分页来加深理解,必竟分页这种功能在平时的项目中还是经常需要;
一:条件查询(Criteria Queries)理论
为了对应HQL的种种查询条件,NHibernate预定义了大量的Expression方法,列几个如下:
Eq = Equal
Gt = Greater than
Lt = Less than
Like
= Like
Not = Not
IsNull = Is Null
1.1 条件查询(Criteria Queries):具有一个直观的、可扩展的条件查询API是NHibernate的特色。NHibernate.ICriteria接口表示特定持久类的一个查询。ISession是 ICriteria 实例的工厂。
//创建关联到某个类的查询对象 ICriteria criteria = session.CreateCriteria(typeof(Person)); //添加表达式 criteria.Add(Expression.Eq("Name","Jackie Chan")); IList list = criteria.List();
Eq是Equal的缩写,意思是添加一个查询表达式,Person.Name = “Jackie Chan”
对应HQL就是:from Person p
where p.Name=”Jackie Chan”
1.1.1 经常还有一个实体里面有多条件查询,也可以如下面写法,简单地new出一个person对象,然后填充其属性即可,不用再去构造那丑陋的条件判断语句了:
ICriteria criteria = session.CreateCriteria(typeof(Person)); Person person = new Person(); person.Name = "Jackie Chan"; person.Age = 50; //创建一个Example对象 criteria.Add(Example.Create(person)); IList list = criteria.List();
1.2 限制结果集内容:一个单独的查询条件是NHibernate.Expression.ICriterion 接口的一个实例。NHibernate.Expression.Expression类 定义了获得某些内置ICriterion类型的工厂方法。
IList cats = sess.CreateCriteria(typeof(Cat)) .Add( Expression.Like("Name", "Fritz%") ) .Add( Expression.Between("Weight", minWeight, maxWeight) ) .List();
1.2.1 约束可以按逻辑分组
IList cats = sess.CreateCriteria(typeof(Cat)) .Add( Expression.Like("Name", "Fritz%") ) .Add( Expression.Or( Expression.Eq( "Age", 0 ), Expression.IsNull("Age") ) ) .List(); IList cats = sess.CreateCriteria(typeof(Cat)) .Add( Expression.In( "Name", new String[] { "Fritz", "Izi", "Pk" } ) ) .Add( Expression.Disjunction() .Add( Expression.IsNull("Age") ) .Add( Expression.Eq("Age", 0 ) ) .Add( Expression.Eq("Age", 1 ) ) .Add( Expression.Eq("Age", 2 ) ) ) ) .List();
1.2.2 允许你直接使用SQL,{alias}占位符应当被替换为被查询实体的列别名
IList cats = sess.CreateCriteria(typeof(Cat)) .Add( Expression.Sql("lower({alias}.Name) like lower(?)", "Fritz%", NHibernateUtil.String ) .List();
1.3 结果集排序:可以使用NHibernate.Expression.Order来为查询结果排序,其方法有两个Order.Asc()及Order.Desc()
IList cats = sess.CreateCriteria(typeof(Cat)) .Add( Expression.Like("Name", "F%") .AddOrder( Order.Asc("Name") ) .AddOrder( Order.Desc("Age") ) .SetMaxResults(50) .List();
1.4 限制记录范围
ICriteria criteria = session.CreateCriteria(typeof(Person)); //从第10条记录开始取 criteria.SetFirstResult(10); //取20条记录 criteria.SetMaxResults(20); IList list = criteria.List();
二:Criteria结合AspNetPager分页实例
分页功能基本上在第一个项目都会出现,能过本实例完成一个简单的分页功能,本文把主要代码贴出来,完整的源代码文章最后提供下载;
2.1 创建一个T_School的表,并创建一个存储过程用于循环插入数据进行分页,脚本如下:
CREATE TABLE [dbo].[T_School]( [ID] [int] IDENTITY(1,1) NOT NULL, [SchoolName] [nvarchar](255) COLLATE Chinese_PRC_CI_AS NULL, [BuildDate] [datetime] NULL, [Address] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL, [IsSenior] [bit] NULL, [StudentNum] [int] NULL, CONSTRAINT [PK_T_School] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY]
Create PROCEDURE [dbo].[Pro_Insert] AS declare @ID int BEGIN set @ID=0 while @ID<200000 begin insert into T_School(SchoolName,BuildDate,Address,IsSenior,StudentNum) VALUES(‘中学教育‘+cast(@ID as varchar),‘2014/3/4 21:49:32‘,‘厦门软件园‘,1,390) set @ID=@ID+1 end END
2.2 在实体层简单定义几个分页要用到的类,对一些属性进行封装,下面只是PageInfo类,其它类的代码大家直接查看源代码;
namespace Wujy.ModelLibrary.Pagination { public class PageInfo { public PageInfo() { } public PageInfo(Type entityType,int pageIndex) { this._entityType = entityType; this._pageIndex = pageIndex; } public PageInfo(Type entityType, int pageIndex,params NCondition[] conditions) { this._entityType = entityType; this._pageIndex = pageIndex; this._conditions = conditions; } public PageInfo(Type entityType, int pageIndex, NCondition[] conditions,NOrder[] orders) { this._entityType = entityType; this._pageIndex = pageIndex; this._conditions = conditions; this._orderFields = orders; } private Type _entityType;//类 public Type EntityType { get { return _entityType; } set { _entityType = value; } } private int _pageIndex = 1;//页号 public int PageIndex { get { return _pageIndex; } set { _pageIndex = value; } } private NCondition[] _conditions;//条件 public NCondition[] Conditions { get { return _conditions; } set { _conditions = value; } } private NOrder[] _orderFields;//排序 public NOrder[] OrderFields { get { return _orderFields; } set { _orderFields = value; } } private int pageSize = 10; public int PageSize { get { return pageSize; } set { pageSize = value; } } private int _recordCount; public int RecordCount { get { return _recordCount; } set { _recordCount = value; } } private int pageCount; public int PageCount { get { return pageCount; } set { pageCount = value; } } private System.Collections.IList list; public IList List { get { return list; } set { list = value; } } } }
2.3 在DAL层里面创建一个基类,把分页的代码写在这里,下面就例出比较重要的几个代码:
public void DoPager(PageInfo pi) { if (pi.EntityType == null) { throw new Exception("分页类名不能为空"); } using (ISession session = new NHibernateHelper().GetSession()) { ICriteria qbc = session.CreateCriteria(pi.EntityType); //总条数 qbc.SetProjection(NHibernate.Criterion.Projections.RowCount()); prepareConditions(qbc, pi.Conditions); pi.RecordCount = qbc .SetMaxResults(1) .UniqueResult<int>(); //总页数 pi.PageCount = pi.RecordCount % pi.PageSize == 0? pi.RecordCount / pi.PageSize: pi.RecordCount / pi.PageSize + 1; //qbc.SetProjection(null); //分页结果 ICriteria _qbc = session.CreateCriteria(pi.EntityType); prepareConditions(_qbc, pi.Conditions); //设置排序 prepareOrder(_qbc, pi.OrderFields); //分页结果 pi.List = _qbc .SetFirstResult((pi.PageIndex - 1) * pi.PageSize) .SetMaxResults(pi.PageSize) .List(); } } /// <summary> /// 处理条件 /// </summary> /// <param name="qbc"></param> /// <param name="conditions"></param> private void prepareConditions(ICriteria qbc,params NCondition[] conditions) { if (qbc == null || conditions == null || conditions.Length == 0) { return; } foreach (NCondition condition in conditions) { switch (condition.Operate) { case Operation.EQ: qbc.Add(Expression.Eq(condition.PropertyName, condition.PropertyValue)); break; case Operation.GT: qbc.Add(Expression.Gt(condition.PropertyName, condition.PropertyValue)); break; case Operation.LT: qbc.Add(Expression.Lt(condition.PropertyName, condition.PropertyValue)); break; case Operation.GE: qbc.Add(Expression.Ge(condition.PropertyName, condition.PropertyValue)); break; case Operation.LE: qbc.Add(Expression.Le(condition.PropertyName, condition.PropertyValue)); break; case Operation.NE: qbc.Add(Expression.Not( Expression.Eq(condition.PropertyName, condition.PropertyValue) )); break; case Operation.BETWEEN: qbc.Add(Expression.Between( condition.PropertyName, (condition.PropertyValue as Object[])[0], (condition.PropertyValue as Object[])[1] ) ); break; case Operation.LIKE: qbc.Add(Expression.Like( condition.PropertyName, condition.PropertyValue.ToString(), MatchMode.Anywhere ) ); break; case Operation.IN: qbc.Add(Expression.In(condition.PropertyName, condition.PropertyValue as object[])); break; } } } /// <summary> /// 处理排序 /// </summary> /// <param name="qbc"></param> /// <param name="orderFields"></param> private void prepareOrder(ICriteria qbc, params Wujy.ModelLibrary.Pagination.NOrder[] orderFields) { if (qbc == null || orderFields == null || orderFields.Length == 0) { return; } foreach (Wujy.ModelLibrary.Pagination.NOrder order in orderFields) { qbc.AddOrder( order.OrderType == Wujy.ModelLibrary.Pagination.NOrder.OrderDirection.ASC ? Order.Asc(order.PropertyName) : Order.Desc(order.PropertyName) ); } }
2.4 UI层结合AspNetPager不带条件
private void BindData() { ModelLibrary.Pagination.PageInfo pi = new ModelLibrary.Pagination.PageInfo(typeof(SchoolModel), this.AspNetPager2.CurrentPageIndex); new PaginationBLL().GetToPager(pi); this.AspNetPager2.RecordCount = pi.RecordCount; this.DataList1.DataSource = pi.List; this.DataList1.DataBind(); this.Label1.Text = "当前第" + this.AspNetPager2.CurrentPageIndex + "页 总" + pi.PageCount + "页"; } protected void AspNetPager2_PageChanged(object sender, EventArgs e) { BindData(); }
效果图:
2.5 UI层结合AspNetPager带条件及排序
private void BindData() { ModelLibrary.Pagination.NCondition[] nclist=new ModelLibrary.Pagination.NCondition[2]; nclist[0] = new ModelLibrary.Pagination.NCondition("SchoolName", ModelLibrary.Pagination.Operation.LIKE, "踏浪帅"); nclist[1] = new ModelLibrary.Pagination.NCondition("StudentNum", ModelLibrary.Pagination.Operation.GE, 390); ModelLibrary.Pagination.NOrder[] orderlist = new ModelLibrary.Pagination.NOrder[1]; orderlist[0]=new ModelLibrary.Pagination.NOrder("StudentNum", ModelLibrary.Pagination.NOrder.OrderDirection.DESC); ModelLibrary.Pagination.PageInfo pi = new ModelLibrary.Pagination.PageInfo(typeof(SchoolModel), this.AspNetPager2.CurrentPageIndex,nclist,orderlist); new PaginationBLL().GetToPager(pi); this.AspNetPager2.RecordCount = pi.RecordCount; this.DataList1.DataSource = pi.List; this.DataList1.DataBind(); this.Label1.Text = "当前第" + this.AspNetPager2.CurrentPageIndex + "页 总" + pi.PageCount + "页"; } protected void AspNetPager2_PageChanged(object sender, EventArgs e) { BindData(); }
效果图:
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NHibernate初学三之条件查询(Criteria Queries)与AspNetPager分页实例,古老的榕树,5-wow.com
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