Spring.NET学习笔记(6)-基础AOP

1.在我们的系统中，常常要对操作进行记录，比如说某某人新增了一笔数据，然后在数据库中增加一笔操作记录

2.前端开发人员往往会在ajax调用后端的时候，调用之前先做一些数据检验的工作，调用之后对于返回的数据ui做出一些反应

3.后端开发人员有时候会做一个数据的ing和ed事件操作,比如插入数据,InsertIng和Inserted事件.

以上的种种反应在进行一个方法的操作，往往还有着其他的关联，这被我们称之为耦合，系统越大，关联越多。再比如添加日志这个功能，某天就不要了，但添加日志的代码与新增数据的代码是写在一起的，这时候就必须做出修改。

对于这些问题，我们就可以用AOP来解决。关于AOP有很多概念，我们直接看代码，不多概念。

1.通知

(1)前后通知和抛错通知，以接口来实现

public class ConsoleLoggingBeforeAdvice : IMethodBeforeAdvice
{
    public void Before(MethodInfo method, object[] args, object target)
    {
        Console.Out.WriteLine("Intercepted call to this method : " + method.Name);
        Console.Out.WriteLine("    The target is       : " + target);
        Console.Out.WriteLine("    The arguments are   : ");
        if(args != null)
        {
            foreach (object arg in args)
            {
                Console.Out.WriteLine("\t: " + arg);
            }
        }
    }
}

public class ConsoleLoggingAfterAdvice : IAfterReturningAdvice
{
    public void AfterReturning(
        object returnValue, MethodInfo method, object[] args, object target)
    {
        Console.Out.WriteLine("This method call returned successfully : " + method.Name);
        Console.Out.WriteLine("    The target was      : " + target);
        Console.Out.WriteLine("    The arguments were  : ");
        if (args != null)
        {
            foreach (object arg in args)
            {
                Console.Out.WriteLine("\t: " + arg);
            }
        }
        Console.Out.WriteLine("    The return value is : " + returnValue);
    }
}

public class ConsoleLoggingThrowsAdvice : IThrowsAdvice
{
    public void AfterThrowing(Exception ex)
    {
        Console.Error.WriteLine(
            String.Format("Advised method threw this exception : {0}", ex.Message));
    }
}

执行每个方法时都会触发通知，注意当设置属性的时候也会触发(因为属性是伪方法)

// Create AOP proxy programmatically.
ProxyFactory factory = new ProxyFactory(new ServiceCommand());
factory.AddAdvice(new ConsoleLoggingBeforeAdvice());
factory.AddAdvice(new ConsoleLoggingAfterAdvice());
factory.AddAdvice(new ConsoleLoggingThrowsAdvice());
ICommand command = (ICommand)factory.GetProxy();

command.Execute();

(2)环绕通知

即以上三个通知的集合，还可以充当拦截器的作用，阻止方法触发

public class ConsoleLoggingAroundAdvice : IMethodInterceptor
{
    public object Invoke(IMethodInvocation invocation)
    {
        Console.Out.WriteLine(String.Format(
            "Intercepted call : about to invoke method '{0}'", invocation.Method.Name));

        object returnValue = invocation.Proceed();

        Console.Out.WriteLine(String.Format(
            "Intercepted call : returned '{0}'", returnValue));

        return returnValue;
    }
}

ProxyFactory factory = new ProxyFactory(new ServiceCommand());
              
factory.AddAdvice(new ConsoleLoggingAroundAdvice());

ICommand command = (ICommand)factory.GetProxy();

command.Execute();
if (command.IsUndoCapable)
{
    command.UnExecute();
}

2.以配置文件方式配置

<object id="aroundAdvice" 
        type="Spring.AopQuickStart.Aspects.ConsoleLoggingAroundAdvice, Spring.AopQuickStart.Common" />
<object id="throwsAdvice" 
        type="Spring.AopQuickStart.Aspects.ConsoleLoggingThrowsAdvice, Spring.AopQuickStart.Common" />

<object id="myServiceCommand" type="Spring.Aop.Framework.ProxyFactoryObject">
  <property name="Target">
    <object type="Spring.AopQuickStart.Commands.ServiceCommand, Spring.AopQuickStart.Common" />
  </property>
  <property name="InterceptorNames">
    <list>
      <value>aroundAdvice</value>
      <value>throwsAdvice</value>
    </list>
  </property>
</object>

3.切入点

即通知在何时(指在某个方法)执行，以上通知是不管调用什么属性和方法都通知，显然我们就需要某几个方法同志就好了，所以需要一个方法匹配的过滤，如下代码NameMatchMethodPointcutAdvisor可进行方法名字过滤，

<object id="aroundAdvisor" type="Spring.Aop.Support.NameMatchMethodPointcutAdvisor, Spring.Aop">
        <property name="Advice">
          <object type="Spring.AopQuickStart.Aspects.ConsoleLoggingAroundAdvice, Spring.AopQuickStart.Common" /> </property> <property name="MappedNames"> <list> <value>*Execute</value> </list> </property> </object>

      <object id="throwsAdvice" 
              type="Spring.AopQuickStart.Aspects.ConsoleLoggingThrowsAdvice, Spring.AopQuickStart.Common" />

      <object id="myServiceCommand" type="Spring.Aop.Framework.ProxyFactoryObject">
        <property name="Target">
          <object type="Spring.AopQuickStart.Commands.ServiceCommand, Spring.AopQuickStart.Common" />
        </property>
        <property name="InterceptorNames">
          <list>
            <value>aroundAdvisor</value>
            <value>throwsAdvice</value>
          </list>
        </property>
      </object>

除了此过滤器，只要实现IPointcutAdvisor接口的都可以，spring还提供了其他的过滤类。

1.RegularExpressionMethodPointcutAdvisor && SdkRegularExpressionMethodPointcut

正则表达式匹配

<object id="settersAndAbsquatulatePointcut"
    type="Spring.Aop.Support.SdkRegularExpressionMethodPointcut, Spring.Aop">
  <property name="patterns">
    <list>
      <value>.*set.*</value>
      <value>.*absquatulate</value>
    </list>
  </property>
</object>

<object id="settersAndAbsquatulateAdvisor"
    type="Spring.Aop.Support.RegularExpressionMethodPointcutAdvisor, Spring.Aop">
  <property name="advice">
    <ref local="objectNameOfAopAllianceInterceptor"/>
  </property>
  <property name="patterns">
    <list>
      <value>.*set.*</value>
      <value>.*absquatulate</value>
    </list>
  </property>
</object>

2.AttributeMatchMethodPointcutAdvisor

在方法上挂标签匹配

<object id="aroundAdvisor" type="Spring.Aop.Support.AttributeMatchMethodPointcutAdvisor, Spring.Aop">
  <property name="Advice">
    <object type="Spring.AopQuickStart.Aspects.ConsoleLoggingAdvice, Spring.AopQuickStart.Step4" />
  </property>
  <property name="Attribute" 
            value="Spring.AopQuickStart.Attributes.ConsoleLoggingAttribute, Spring.AopQuickStart.Step4" />
</object>