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MVC项目实践,在三层架构下实现SportsStore-02,DbSession层、BLL层
SportsStore是《精通ASP.NET MVC3框架(第三版)》中演示的MVC项目,在该项目中涵盖了MVC的众多方面,包括:使用DI容器、URL优化、导航、分页、购物车、订单、产品管理、图像上传......是不错的MVC实践项目,但该项目不是放在多层框架下开发的,离真实项目还有一段距离。本系列将尝试在多层框架下实现SportsStore项目,并用自己的方式实现一些功能。
本篇为系列第二篇,包括:
■ 4、三层架构设计
□ 4.2 创建DbSession层 数据访问层的统一入口
※ 4.2.1 MySportsStore.IDAL详解
※ 4.2.2 MySportsStore.DAL详解
□ 4.3 创建BLL层
※ 4.3.1 MySportsStore.IBLL详解
※ 4.3.2 MySportsStore.BLL详解
4.2 创建DbSession层 数据访问层的统一入口
DbSession层主要做了3件事:
1、提交所有变化
2、拿到各个IXXXRepository类型
3、执行SQL语句
4.2.1 MySportsStore.IDAL详解
→IDbSession接口,数据库访问层的统一入口
using System.Data.SqlClient;namespace MySportsStore.IDAL{ public interface IDbSession { //获取所有的仓储接口 IProductRepository ProductRepository { get; set; } //保存所有变化 int SaveChanges(); //执行sql语句 int ExeucteSql(string sql, params SqlParameter[] paras); }}
→IDbSessionFactory接口,IDbSession接口的抽象工厂
在BaseRepository中会用到IDbSession的实例,我们借助"抽象工厂"生产IDbSession的实例。
namespace MySportsStore.IDAL{ public interface IDbSessionFactory { IDbSession GetCurrentDbSession(); }}
4.2.2 MySportsStore.DAL详解
→DbSession,对IDbSession接口的实现
using System.Data.Entity;using MySportsStore.IDAL;namespace MySportsStore.DAL{ public class DbSession : IDbSession { private IProductRepository _ProductRepository; public IProductRepository ProductRepository { get { if (_ProductRepository == null) { _ProductRepository = new ProductRepository(); } return _ProductRepository; } set { _ProductRepository = value; } } public int SaveChanges() { IDbContextFactory dbFactory = new DbContextFactory(); DbContext db = dbFactory.GetCurrentThreadInstance(); return db.SaveChanges(); } public int ExeucteSql(string sql, params System.Data.SqlClient.SqlParameter[] paras) { IDbContextFactory dbFactory = new DbContextFactory(); DbContext db = dbFactory.GetCurrentThreadInstance(); return db.Database.ExecuteSqlCommand(sql, paras); } }}
→DbSessionFactory,实现IDbSessionFactory接口,生产线程内唯一数据层访问入口实例
using System.Runtime.Remoting.Messaging;using MySportsStore.IDAL;namespace MySportsStore.DAL{ public class DbSessionFactory: IDbSessionFactory { public IDbSession GetCurrentDbSession() { IDbSession dbSession = CallContext.GetData(typeof (DbSession).FullName) as IDbSession; if (dbSession == null) { dbSession = new DbSession(); CallContext.SetData(typeof(DbSession).FullName, dbSession); } return dbSession; } }}
4.3 创建BLL层
4.3.1 MySportsStore.IBLL详解
→添加引用
● 添加对MySportsStore.Model的引用
● 添加对MySportsStore.IDAL的引用
→IBaseService,是所有IXXXService接口的泛型基接口实现,避免了所有IXXXService接口的重复部分
using System;using System.Linq;using System.Linq.Expressions;using MySportsStore.IDAL;namespace MySportsStore.IBLL{ public interface IBaseService<T> where T : class, new() { //数据层访问统一入口工厂 IDbSessionFactory DbSessionFactory { get; set; } //数据层访问统一入口 IDbSession DbSessionContext { get; set; } //查询 IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda); //分页查询 IQueryable<T> LoadPageEntities<S>( Expression<Func<T, bool>> whereLambada, Expression<Func<T, S>> orderBy, int pageSize, int pageIndex, out int totalCount, bool isASC); //查询总数量 int Count(Expression<Func<T, bool>> predicate); //添加 T AddEntity(T entity); //批量添加 int AddEntities(params T[] entities); //删除 int DeleteEntity(T entity); //批量删除 int DeleteBy(Expression<Func<T, bool>> whereLambda); //更新 T UpdateEntity(T entity); //批量更新 int UpdateEntities(params T[] entities); }}
为什么需要DbSessionContext属性?
--通过该属性可以拿到类型为IXXXRepository的XXXRepository。
为什么需要DbSessionFactory属性?
--通过该"抽象工厂"属性可以生产DbSessionContext实例。
→IProductService,对基接口IBaseService<Product>的实现
using MySportsStore.Model;namespace MySportsStore.IBLL{ public interface IProductService : IBaseService<Product> { }}
4.3.2 MySportsStore.BLL详解
→添加引用
● 添加对MySportsStore.Model的引用
● 添加对MySportsStore.IDAL的引用
● 添加对MySportsStore.IBLL的引用
→BaseService
using System;using System.Collections.Generic;using System.Linq;using System.Linq.Expressions;using MySportsStore.DAL;using MySportsStore.IDAL;namespace MySportsStore.BLL{ public abstract class BaseService<T> : IDisposable where T:class,new() { //数据层统一访问入口工厂属性 private IDbSessionFactory _DbSessionFactory; public IDbSessionFactory DbSessionFactory { get { if (_DbSessionFactory == null) { _DbSessionFactory = new DbSessionFactory(); } return _DbSessionFactory; } set { _DbSessionFactory = value; } } //数据层统一访问入口属性 private IDbSession _DbSessionContext; public IDbSession DbSessionContext { get { if (_DbSessionContext == null) { _DbSessionContext = DbSessionFactory.GetCurrentDbSession(); } return _DbSessionContext; } set { _DbSessionContext = value; } } //当前Repository,在子类中实现--通过一个抽象方法在构造函数中设置 protected IBaseRepository<T> CurrentRepository; //借助此方法在子类中的重写,为XXXService设置当前Repository public abstract bool SetCurrentRepository(); public BaseService() { this.DisposableObjects = new List<IDisposable>(); this.SetCurrentRepository(); } //查询 public IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda) { return this.CurrentRepository.LoadEntities(whereLambda); } public IQueryable<T> LoadPageEntities<S>( Expression<Func<T, bool>> whereLambada, Expression<Func<T, S>> orderBy, int pageSize, int pageIndex, out int totalCount, bool isASC) { return this.CurrentRepository.LoadPageEntities<S>( whereLambada, orderBy, pageSize, pageIndex, out totalCount, isASC); } //查询总数量 public int Count(Expression<Func<T, bool>> predicate) { return this.CurrentRepository.Count(predicate); } //添加 public T AddEntity(T entity) { this.CurrentRepository.AddEntity(entity); DbSessionContext.SaveChanges(); return entity; } //批量添加 public int AddEntities(params T[] entities) { return this.CurrentRepository.AddEntities(entities); } //删除 public int DeleteEntity(T entity) { this.CurrentRepository.DeleteEntity(entity); return DbSessionContext.SaveChanges(); } //批量删除 public int DeleteBy(Expression<Func<T, bool>> whereLambda) { this.CurrentRepository.DeleteBy(whereLambda); return DbSessionContext.SaveChanges(); } //更新 public T UpdateEntity(T entity) { this.CurrentRepository.UpdateEntity(entity); if (this.DbSessionContext.SaveChanges() <= 0) { return null; } return entity; } //批量更新 public int UpdateEntities(params T[] entities) { return this.CurrentRepository.UpdateEntities(entities); } public IList<IDisposable> DisposableObjects { get; private set; } protected void AddDisposableObject(object obj) { IDisposable disposable = obj as IDisposable; if (disposable != null) { this.DisposableObjects.Add(disposable); } } public void Dispose() { foreach (IDisposable obj in this.DisposableObjects) { if (obj != null) { obj.Dispose(); } } } }}
BaseService是所有XXXService的泛型基类实现。
关键点一:如何在BaseService的子类中确定当前存储CurrentRepository?
1、抽象基类BaseServic有类型为 IBaseRepository<T>的属性CurrentRepository
2、通过在抽象基类BaseServic的构造函数中实现抽象方法SetCurrentRepository(),来设置CurrentRepository
3、BaseServic的子类必须重写SetCurrentRepository()以最终确定当前的CurrentRepository值
关键点二:如何把BaseService的子类中的CurrentRepository销毁?
1、在BaseService创建一个类型为IList<IDisposable>的集合
2、在BaseService中提供一个AddDisposableObject(object obj)方法,允许子类把CurrentRepository放入其中
3、在BaseService的Dispose()方法中,遍历所有的CurrentRepository进行销毁
→ProductService,派生于BaseService<Product>,实现IProductService接口
using MySportsStore.IBLL;using MySportsStore.Model;namespace MySportsStore.BLL{ public class ProductService : BaseService<Product>, IProductService { public ProductService():base(){} public override bool SetCurrentRepository() { this.CurrentRepository = DbSessionContext.ProductRepository; this.AddDisposableObject(this.CurrentRepository); return true; } }}
至此,完成了三层架构的代码实现。
“MVC项目实践,在三层架构下实现SportsStore”系列包括: