01-04-03【Nhibernate (版本3.3.1.4000) 出入江湖】Criteria API关联查询

Criteria API关联查询

如果说HQL查询还有需要了解点SQL语法知识，并不是完全彻底面向对象查询，

那么Criterial API就是完全面向对象的查询方式。

 public IList<Customer> UseCriteriaAPI_GetCustomersWithOrders(DateTime orderDate)
 {
     return _session.CreateCriteria(typeof(Customer))
          .Add(Restrictions.Eq("FirstName", "easy5")) //为本表查询添加查询参数
         .CreateCriteria("Orders") //关联查询Order表开始，注意：“Oreders”是类Customer中关联到Order类的属性
          .Add(Restrictions.Gt("OrderDate", orderDate))//OrderDate是Order类中的属性，不是数据库表Order的列名，如果是列名就不是面向对象编程了

          .List<Customer>();  

 }

我们使用CreateCriteria()在关联之间导航，很容易地在实体之间指定约束。

这里第二个CreateCriteria()返回一个ICriteria的新实例，并指向Orders实体的元素。

在查询中子对象使用子CreateCriteria语句，这是因为实体之间的关联我们在映射文件中已经定义好了。

还有一种方法使用CreateAlias()不会创建ICriteria的新实例。

预过滤

使用ICriteria接口的SetResultTransformer(IResultTransformer resultTransformer)方法返回满足特定条件的Customer。上面例子中使用条件查询，观察其生成的SQL语句并没有distinct，这时可以使用NHibernate.Transform命名空间中的方法或者使用NHibernate提供的NHibernate.CriteriaUtil.RootEntity、NHibernate.CriteriaUtil.DistinctRootEntity、NHibernate.CriteriaUtil.AliasToEntityMap静态方法实现预过滤的作用。那么上面的查询应该修改为：

public IList<Customer> UseCriteriaAPI_GetCustomersWithOrders(DateTime orderDate)

{

    return _session.CreateCriteria(typeof(Customer))

        .CreateCriteria("Orders")

        .Add(Restrictions.Gt("OrderDate", orderDate))

        .SetResultTransformer(new NHibernate.Transform.DistinctRootEntityResultTransformer()) //过滤重复项

        .List<Customer>();

}

这个例子从转换结果集的角度实现了我们想要的效果。

投影

调用SetProjection()方法可以实现应用投影到一个查询中。NHibernate.Criterion.Projections是Projection的实例工厂，Projections提供了非常多的方法，看看下面的截图

现在可以条件查询提供的投影来完成上面同样的目的：

public IList<Customer> UseCriteriaAPI_GetDistinctCustomers(DateTime orderDate)

{

IList<int> ids = _session.CreateCriteria(typeof(Customer))

.SetProjection(Projections.Distinct(Projections.ProjectionList()

.Add(Projections.Property("CustomerId"))

)

)

.CreateCriteria("Orders")

.Add(Restrictions.Gt("OrderDate", orderDate))

.List<int>();

return _session.CreateCriteria(typeof(Customer))

.Add(Restrictions.In("CustomerId", ids.ToArray<int>()))

.List<Customer>();

}

我们可以添加若干的投影到投影列表中，例如这个例子我添加一个CustomerId属性值到投影列表中，这个列表中的所有属性值都设置了Distinct投影，第一句返回订单时间在orderDate之后所有顾客Distinct的CustomerId，第二句根据返回的CustomerId查询顾客列表。达到上面的目的。这时发现其生成的SQL语句中有distinct。我们使用投影可以很容易的组合我们需要的各种方法。

范例：

  #region CriterialAPI 查询

         public IList<Customer> GetEntitysByDateTimeCriterialApi(DateTime dateTime)
         {
             IList<Customer> result = null;
             ISession session = _sessionManager.GetSession();

             result = session.CreateCriteria(typeof(Customer))
                 .CreateCriteria("Orders")
                 .Add(Restrictions.Gt("OrderDate", dateTime))
                 .List<Customer>();

             return result;
         }

         /// <summary>
         /// 利用CreiteriaAPI进行的IN关键字的查询测试
         /// </summary>
         public IList<Customer> UseCreiteriaAPI_IN_Query()
         {
             ISession session = _sessionManager.GetSession();
             // return session.CreateCriteria(typeof(Customer)).CreateCriteria("Orders").Add(Restrictions.Between("OrderDate", startDate, endDate))
             // .List<Customer>();

             object[] firstnames = { "zhang", "li" };
             return session.CreateCriteria(typeof(Customer))
                 .Add(Restrictions.In("FirstName", firstnames))
                 .List<Customer>();

             //return null;
         }

         /// <summary>
         /// 利用CreiteriaAPI进行的Or关键字的查询测试
         /// </summary>
         public IList<Customer> UseCreiteriaAPI_Or_Query()
         {
             ISession session = _sessionManager.GetSession();
             String[] firstnames = { "zhang", "li" };
             return session.CreateCriteria(typeof(Customer))
                 .Add(Restrictions.Or(Restrictions.Eq("FirstName", "zhang"), Restrictions.Eq("FirstName", "li")))
                 .List<Customer>();
         }

         //CriteriaAPI的预过滤测试
         public IList<Customer> UseCriteriaAPI_GetCustomersWithOrders(DateTime orderDate)
         {
             ISession session = _sessionManager.GetSession();

             return session.CreateCriteria(typeof(Customer))
                 .CreateCriteria("Orders")
                 .Add(Restrictions.Gt("OrderDate", orderDate))
                 .SetResultTransformer(new NHibernate.Transform.DistinctRootEntityResultTransformer()) //Distinct--过滤重复项

                 .List<Customer>();
         }

         //CriteriaAPI的Projection投影测试
         public IList<Customer> UseCriteriaAPI_GetDistinctCustomers(DateTime orderDate)
         {
             ISession session = _sessionManager.GetSession();

             IList<int> ids = session.CreateCriteria(typeof(Customer))
                 .SetProjection(Projections.Distinct(Projections.ProjectionList().Add(Projections.Property("CustomerId"))
                 ))
                 .CreateCriteria("Orders")
                 .Add(Restrictions.Gt("OrderDate", orderDate))
                 .List<int>();

             return session.CreateCriteria(typeof(Customer))
                 .Add(Restrictions.In("CustomerId", ids.ToArray<int>()))
                 .List<Customer>();
         }

         //CriteriaAPI的Projection投影测试
         public IList<Object[]> UseCriteriaAPI_GetDistinctCustomers2()
         {
             ISession session = _sessionManager.GetSession();

             return session.CreateCriteria(typeof(Customer))
                 .SetProjection(Projections.ProjectionList()
                 .Add(Projections.Property("FirstName")).Add(Projections.Property("LastName")))
                 .List<Object[]>();

         }

         #endregion

动态查询---关联查询：

         public IList<Customer> UseCriteriaApiAdvQuery(String firstName,
             String lastName,
             DateTime dateTime)
         {
             ICriteria criteria = _session.CreateCriteria("Customer");
             if (null != firstName)
             {
                 criteria.Add(Restrictions.Eq("FirstName", firstName));
             }
             if (null != lastName)
             {
                 criteria.Add(Restrictions.Eq("LastName", lastName));
             }

             if (null != dateTime)
             {
                 //关联查询Order
                 // 注意：不是criteria.CreateCriteria("Order")，如果是，会抛异常：
                 //{"could not resolve property: Order of: Model.Customer"}
                 //而是criteria.CreateCriteria("Orders")，Orders是Customer类在关联的Order类的属性
                 criteria.CreateCriteria("Orders").Add(Restrictions.Eq("OrderDate", dateTime));
             }

             return criteria.List<Customer>();
         }

 测试代码：

         [TestMethod]
         public void TestUseCriteriaApiADvQuery()
         {
             CustomerService customerService = new CustomerService();
             OrderService orderService = new OrderService();

             Customer customer = new Customer()
             {
                 FirstName = "Test",
                 LastName = "TestUseCriteriaApiADvQuery",
                 Age =
             };

             Order order1 = new Order()
             {
                 OrderDate = DateTime.Now,
                 Customer = customer
             };

             customer.Orders.Add(order1);
             customerService.Add(customer);

             Assert.IsNotNull(customerService.Find(customer.CustomerId));
             Assert.IsNotNull(orderService.Find(order1.OrderId));

             IList<Customer> customers =
                 customerService.UseCriteriaApiAdvQuery(customer.FirstName,
                 customer.LastName, order1.OrderDate);

             Assert.IsTrue(customers.Count > );
         }

动态查询---模糊查询：

        #region CriterialAPI 动态+模糊查询

        public IList<Customer> UseCriteriaApiLikeQuery(String firstName,
            String lastName)
        {
            ICriteria criteria = _session.CreateCriteria("Customer");
            if (null != firstName)
            {
                //方式一：用原生的匹配字符,如：%
                criteria.Add(Restrictions.Like("FirstName", "%" + firstName +"%"));
            }
            if (null != lastName)
            {
                //方式二：用MatchMode
                criteria.Add(Restrictions.Like("LastName", lastName, MatchMode.Anywhere));
            }

            return criteria.List<Customer>();
        }

        #endregion

测试代码：

        #region 测试CriteriaAPI查询--动态 + 模糊查询

        [TestMethod]
        public void TestUseCriteriaApiLikeQuery()
        {
            CustomerService customerService = new CustomerService();
            OrderService orderService = new OrderService();

            Customer customer = new Customer()
            {
                FirstName = "Test",
                LastName = "TestUseCriteriaApiLikeQuery",
                Age =
            };

            Order order1 = new Order()
            {
                OrderDate = DateTime.Now,
                Customer = customer
            };

            customer.Orders.Add(order1);
            customerService.Add(customer);

            Assert.IsNotNull(customerService.Find(customer.CustomerId));
            Assert.IsNotNull(orderService.Find(order1.OrderId));

            IList<Customer> customers =
                customerService.UseCriteriaApiLikeQuery(null,
                "CriteriaApiLike");

            Assert.IsTrue(customers.Count > );
        }

        #endregion

排序：

        /// <summary>
        /// 模糊查询+排序
        /// </summary>
        /// <param name="firstName"></param>
        /// <param name="lastName"></param>
        /// <returns></returns>
        public IList<Customer> UseCriteriaApiLikeQueryAndDescOrder(String firstName,
            String lastName)
        {
            ICriteria criteria = _session.CreateCriteria("Customer");
            if (null != firstName)
            {
                //方式一：用原生的匹配字符,如：%
                criteria.Add(Restrictions.Like("FirstName", "%" + firstName +"%"));
            }
            if (null != lastName)
            {
                //方式二：用MatchMode
                criteria.Add(Restrictions.Like("LastName", lastName, MatchMode.Anywhere))
                        .AddOrder(NHibernate.Criterion.Order.Desc("CustomerId"));
            }

            return criteria.List<Customer>();
        }

        #endregion

测试代码：

        [TestMethod]
        public void TestUseCriteriaApiLikeQueryAndDescOrder()
        {
            CustomerService customerService = new CustomerService();
            OrderService orderService = new OrderService();

            Customer customer1 = new Customer()
            {
                FirstName = "Test",
                LastName = "TestUseCriteriaApiLikeQuery1",
                Age =
            };

            Customer customer2 = new Customer()
            {
                FirstName = "Test",
                LastName = "TestUseCriteriaApiLikeQuery2",
                Age =
            };

            customerService.Add(customer1);
            customerService.Add(customer2);
            Assert.IsNotNull(customerService.Find(customer1.CustomerId));
            Assert.IsNotNull(customerService.Find(customer2.CustomerId));

            IList<Customer> customers =
                customerService.UseCriteriaApiLikeQueryAndDescOrder(null, "CriteriaApiLike");

            Assert.IsTrue(customer1.CustomerId < customer2.CustomerId);
            Assert.IsTrue(customers[].LastName== customer2.LastName);
        }