使用Microsoft.Practices.Unity 依赖注入

Unity是微软Patterns & Practices团队所开发的一个轻量级的，并且可扩展的依赖注入(Dependency Injection)容器，它支持常用的三种依赖注入方式：构造器注入(Constructor Injection)、属性注入(Property Injection)，以及方法调用注入(Method Call Injection).

假设我们有下面的场景代码，在代码里面有一个很简单的customer对象，customer 对象有个save 方法， 这个方法通过调用ICustomerDataAccess.Save将数据持久到数据库中, 在列子中我们实现了dataaccess的sql版本和mysql版本，也就是说我们这个customer对象，可以支持持久化到sql server 或 mysql.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Practices.Unity;

namespace UnitySample
{
    public interface ICustomerDataAccess
    {
        void Save(Customer c);
    }

    public class CustomerSqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.Write("{2}, save data id:{0},name{1}",c.Id,c.Name,this.GetType().ToString());
        }
    }

    public class CustomerMysqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.Write("{2}, save data id:{0},name{1}", c.Id, c.Name, this.GetType().ToString());
        }
    }

    public class Customer
    {
        public ICustomerDataAccess CustomerDataAccess { get; set; }

        public string Id { get; set; }
        public string Name { get; set; }

        public void Save()
        {
            CustomerDataAccess.Save(this);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {

        }
    }
}

传统做法可能是在配置文件中填几个一个变量 dbType = sql  or my sql. 然后在customer 对象中根据设定的db type 来实力化不同的dataaccess.

代码可能会是下面这个样子，这样的话，customer 对象实际上依赖于CustomerSqlDataAccess 和 CustomerSqlDataAccess 的，而且，未来比如要新增加其他数据库的支持，则必须修改customer 对象的源代码。

 public Customer()
 {
            if (DbType = "sql")
            {
                CustomerDataAccess = new CustomerSqlDataAccess();
            }
            else
            {
                CustomerDataAccess = new CustomerSqlDataAccess();
            }
 }

下面我们使用unity 来解除customer 对象对  CustomerSqlDataAccess 和 CustomerSqlDataAccess 的依赖。

一、 属性注入(Property Injection)

1.  配置unity

　　   为了以后调用方便，我这里建立了一个静态方法，然后注入了两个dataaccess。

 public class UnitySetup
    {
        public static void Config()
        {
            var container = new UnityContainer();
            container.RegisterType<ICustomerDataAccess, CustomerSqlDataAccess>();
            container.RegisterType<ICustomerDataAccess, CustomerSqlDataAccess>("mysql");
        }
    }

　　然后我们需要在Main函数中调用这个方法配置unity containter.

　　

　　　　　static void Main(string[] args)
        {
            UnitySetup.Config();
        }

2. 标记属性注入

　　 这步很简单，直接在customer 类中的ICustomerDataAccess 定义上面添加[Dependency]标注即可。

[Dependency]
public ICustomerDataAccess CustomerDataAccess { get; set; }

3. 通过resove 获取对象

            var container = new UnityContainer();
            UnitySetup.Config(container);
            var sqlCustomer = container.Resolve<ICustomerDataAccess>();
            var mysqlCustomer = container.Resolve<ICustomerDataAccess>("mysql");

上面的代码就分别获取了CustomerSqlDataAccess 实例和CustomerSqlDataAccess实例

二 、构造器注入(Constructor Injection)

1.  配置unity

　　

  unityContainer.RegisterType<Customer>(
                new InjectionConstructor(new ResolvedParameter<ICustomerDataAccess>()));
            unityContainer.RegisterType<Customer>("mysqlCustomer",
                new InjectionConstructor(new ResolvedParameter<ICustomerDataAccess>("mysql")));

添加两行注册customer 对想到container.

2. 获取

 var sqlCustomer = container.Resolve<Customer>();
 var myqlCustomer = container.Resolve<Customer>("mysqlCustomer");

完整代码如下

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Practices.Unity;

namespace UnitySample
{

    public interface ICustomerDataAccess
    {
        void Save(Customer c);
    }

    public class CustomerSqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.WriteLine("{2}, save data id:{0},name{1}",c.Id,c.Name,this.GetType().ToString());
        }
    }

    public class CustomerMysqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.WriteLine("{2}, save data id:{0},name{1}", c.Id, c.Name, this.GetType().ToString());
        }
    }

    public class UnitySetup
    {
        public static void Config(IUnityContainer unityContainer)
        {
            unityContainer.RegisterType<ICustomerDataAccess, CustomerSqlDataAccess>();
            unityContainer.RegisterType<ICustomerDataAccess, CustomerMysqlDataAccess>("mysql");
            unityContainer.RegisterType<Customer>(
                new InjectionConstructor(new ResolvedParameter<ICustomerDataAccess>()));
            unityContainer.RegisterType<Customer>("mysqlCustomer",
                new InjectionConstructor(new ResolvedParameter<ICustomerDataAccess>("mysql")));
        }
    }

    public class Customer
    {
        private ICustomerDataAccess CustomerDataAccess { get; set;}

        public string Id { get; set; }
        public string Name { get; set; }

        public Customer(ICustomerDataAccess customerDataAccess)
        {
            CustomerDataAccess = customerDataAccess;
        }
        public void Save()
        {
            CustomerDataAccess.Save(this);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var container = new UnityContainer();
            UnitySetup.Config(container);
            var sqlCustomer = container.Resolve<Customer>();
            var myqlCustomer = container.Resolve<Customer>("mysqlCustomer");

            sqlCustomer.Save();
            myqlCustomer.Save();

            Console.ReadKey();
        }
    }
}

三 、 方法调用注入(Method Call Injection)

方法调用注入和输入注入有点类似，只需要在调用的方法上面添加[InjectionMethod] 标注即可

1.  配置unity

　　

 unityContainer.RegisterType<Customer>("mysqlCustomer",
                new InjectionMethod("SetDataAccess", new ResolvedParameter<ICustomerDataAccess>("mysql")));

2. 获取

 var sqlCustomer = container.Resolve<Customer>();
 var myqlCustomer = container.Resolve<Customer>("mysqlCustomer");

完成后的代码如下

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Practices.Unity;

namespace UnitySample
{

    public interface ICustomerDataAccess
    {
        void Save(Customer c);
    }

    public class CustomerSqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.WriteLine("{2}, save data id:{0},name{1}",c.Id,c.Name,this.GetType().ToString());
        }
    }

    public class CustomerMysqlDataAccess : ICustomerDataAccess
    {
        public void Save(Customer c)
        {
            Console.WriteLine("{2}, save data id:{0},name{1}", c.Id, c.Name, this.GetType().ToString());
        }
    }

    public class UnitySetup
    {
        public static void Config(IUnityContainer unityContainer)
        {
            unityContainer.RegisterType<ICustomerDataAccess, CustomerSqlDataAccess>();
            unityContainer.RegisterType<ICustomerDataAccess, CustomerMysqlDataAccess>("mysql");

            unityContainer.RegisterType<Customer>("mysqlCustomer",
                new InjectionMethod("SetDataAccess", new ResolvedParameter<ICustomerDataAccess>("mysql")));
        }
    }

    public class Customer
    {
        private ICustomerDataAccess CustomerDataAccess { get; set;}
        public string Id { get; set; }
        public string Name { get; set; }

        public void Save()
        {
            CustomerDataAccess.Save(this);
        }

        [InjectionMethod]
        public void SetDataAccess(ICustomerDataAccess dataAccess)
        {
            CustomerDataAccess = dataAccess;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var container = new UnityContainer();
            UnitySetup.Config(container);
            var sqlCustomer = container.Resolve<Customer>();
            var mysqlCustomer = container.Resolve<Customer>("mysqlCustomer");
            sqlCustomer.Save();
            mysqlCustomer.Save();
            Console.ReadKey();
        }
    }
}

好了，通过使用unity 依赖注入，customer 对象不再依赖具体的CustomerSqlDataAccess 和 CustomerMysqlDataAccess., 只依赖于接口ICustomerDataAccess。

上面就是unity 的基本用法介绍。