在.net实现AOP
本文通过一个简单的例子实现静态AOP.改例子主要实现客户的增删改查，突然有一天你的老板需要在程序上跟踪每个方法操作的运行日志。
主要分为5个步骤。
第一步：创建接口IRepository<T>，代码定义如下：
public interface IRepository<T>
{
void Add(T entity);
void Delete(T entity);
void Update(T entity);
IEnumerable<T> GetAll();
T GetById(int id);
}
第2步： 创建Repository<T>类，实现代码IRepository<T>，代码如下：
public class Repository<T> : IRepository<T>
{
public void Add(T entity)
{
Console.WriteLine("Adding {0}", entity);
}
public void Delete(T entity)
{
Console.WriteLine("Deleting {0}", entity);
}
public void Update(T entity)
{
Console.WriteLine("Updating {0}", entity);
}
public IEnumerable<T> GetAll()
{
Console.WriteLine("Getting entities");
return null;
}
public T GetById(int id)
{
Console.WriteLine("Getting entity {0}", id);
return default(T);
}
}
第3步，用Repository<T>实现Customer 的增删改查，Customer 定义如下：
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
}
第4步，在控制台程序，运行，代码看起来如下：
static void Main(string[] args)
{
Console.WriteLine("***\r\n Begin program - no logging\r\n");
IRepository<Customer> customerRepository =new Repository<Customer>();
var customer = new Customer
{
Id = 1,
Name = "Customer 1",
Address = "Address 1"
};
customerRepository.Add(customer);
customerRepository.Update(customer);
customerRepository.Delete(customer);
Console.WriteLine("\r\nEnd program - no logging\r\n***");
Console.ReadLine();
}
按F5运行，运行结果如下图：
现在假如你的老板，需要在类中增加日志功能，你可以新建一个LoggerRepository<T>类，让他同样实现IRepository<T>，代码如下：
public class LoggerRepository<T> : IRepository<T>
{
private readonly IRepository<T> _decorated;
public LoggerRepository(IRepository<T> decorated)
{
_decorated = decorated;
}
private void Log(string msg, object arg = null)
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine(msg, arg);
Console.ResetColor();
}
public void Add(T entity)
{
Log("In decorator - Before Adding {0}", entity);
_decorated.Add(entity);
Log("In decorator - After Adding {0}", entity);
}
public void Delete(T entity)
{
Log("In decorator - Before Deleting {0}", entity);
_decorated.Delete(entity);
Log("In decorator - After Deleting {0}", entity);
}
public void Update(T entity)
{
Log("In decorator - Before Updating {0}", entity);
_decorated.Update(entity);
Log("In decorator - After Updating {0}", entity);
}
public IEnumerable<T> GetAll()
{
Log("In decorator - Before Getting Entities");
var result = _decorated.GetAll();
Log("In decorator - After Getting Entities");
return result;
}
public T GetById(int id)
{
Log("In decorator - Before Getting Entity {0}", id);
var result = _decorated.GetById(id);
Log("In decorator - After Getting Entity {0}", id);
return result;
}
}
这个新类，已经包装了包装类，实现日志记录功能，现在需要做小的改动，代码实现如下：
static void Main(string[] args)
{
Console.WriteLine("***\r\n Begin program - logging with decorator\r\n");
// IRepository<Customer> customerRepository =
// new Repository<Customer>();
IRepository<Customer> customerRepository =
new LoggerRepository<Customer>(new Repository<Customer>());
var customer = new Customer
{
Id = 1,
Name = "Customer 1",
Address = "Address 1"
};
customerRepository.Add(customer);
customerRepository.Update(customer);
customerRepository.Delete(customer);
Console.WriteLine("\r\nEnd program - logging with decorator\r\n***");
Console.ReadLine();
}
继续运行，运行结果如下：
到此为止，你可能会想:OK,这个想法是好的,但它仍然需要做很多工作:我必须实现所有的类和添加方面的所有方法。这将是难以维护。
有另一种方式去做吗？.net框架,您可以使用反射来得到所有方法和执行它们。基类库(BCL)甚至有RealProxy类(bit.ly/18MfxWo),为你实现。
答案：是的有的就是我们所讲的动态代理实现AOP; 我们将在下一节讲
AOP参考
本文翻译自 ：https://msdn.microsoft.com/en-us/magazine/dn574804.aspx（面向切面编程）