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<p class="a6" style="MARGIN-TOP: 8.15pt; BACKGROUND: #f2f2f2; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US" style="COLOR: black"> Hello obj = (Hello)RemotingServices.Connect(typeof(Hello), </span></p>
<p class="a6" style="MARGIN-TOP: 0cm; BACKGROUND: #f2f2f2; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US" style="COLOR: black"> "tcp://localhost:8086/Hi");</span></p>
<p class="MsoNormal"><span style="COLOR: black; FONT-FAMILY: 宋体">如果要使用简单的运算符</span><span lang="EN-US" style="COLOR: black">new</span><span style="COLOR: black; FONT-FAMILY: 宋体">去激活知名的远程对象，则必须在客户机上使用</span><span lang="EN-US" style="COLOR: black">RemotingConfiguration.RegisterWellKnownClientType()</span><span style="COLOR: black; FONT-FAMILY: 宋体">注册远程对象。这里需要的参数与上面的相似：即都需要远程对象的类型和</span><span lang="EN-US" style="COLOR: black">URI</span><span style="COLOR: black; FONT-FAMILY: 宋体">。运算符</span><span lang="EN-US" style="COLOR: black">new</span><span style="COLOR: black; FONT-FAMILY: 宋体">实际上并没有创建新的远程对象，而是返回一个与</span><span lang="EN-US" style="COLOR: black">Activator.GetObject()</span><span style="COLOR: black; FONT-FAMILY: 宋体">相似的代理对象。如果使用</span><span lang="EN-US" style="COLOR: black">WellKnownObjectMode.SingleCall</span><span style="COLOR: black; FONT-FAMILY: 宋体">标记注册远程对象，规则总是一样的：即使用每一个方法调用创建远程对象。</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; BACKGROUND: #f2f2f2; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US" style="COLOR: black"> RemotingConfiguration.RegisterWellKnownClientType(typeof(Hello),</span></p>
<p class="a6" style="BACKGROUND: #f2f2f2; MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US" style="COLOR: black"> "tcp://localhost:8086/Hi");</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; BACKGROUND: #f2f2f2; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US" style="COLOR: black"> Hello obj = new Hello();</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-US">3. </span><span style="FONT-FAMILY: 黑体">激活</span><span lang="EN-US">Client-Activated</span><span style="FONT-FAMILY: 黑体">对象</span></h4>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">远程对象可以为客户保存状态。</span><span lang="EN-US">Activator.CreateInstance()</span><span style="FONT-FAMILY: 宋体">用于创建客户激活的远程对象。使用</span><span lang="EN-US">Activator.GetObject()</span><span style="FONT-FAMILY: 宋体">方法，可以在方法调用时创建远程对象，而当方法执行完时，可以删除远程对象。对象不在服务器上保存状态，这一点与</span><span lang="EN-US">Activator.CreateInstance()</span><span style="FONT-FAMILY: 宋体">不同。使用静态的</span><span lang="EN-US">CreateInstance()</span><span style="FONT-FAMILY: 宋体">方法，按次序开始激活，进而创建远程对象。在租约时间到期并且垃圾收集发挥作用之前，对象将一直处于激活状态。本章后面的内容中将讨论租约机制。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">一些重载的</span><span lang="EN-US">Activator.CreateInstance()</span><span style="FONT-FAMILY: 宋体">方法只能用于创建本地对象。为了创建远程的对象，就需要一个能够传送激活属性的方法。我们的示例中就使用了一个重载的方法，该方法接收两个字符串参数，第一个参数是程序集的名称，第二个参数是类型，第三个参数是对象数组。在</span><span lang="EN-US">UrlAttribute</span><span style="FONT-FAMILY: 宋体">的帮助下，可以在对象数组中指定信道和对象的名称。为了使用</span><span lang="EN-US">UrlAttribute</span><span style="FONT-FAMILY: 宋体">类，必须指定命名空间</span><span lang="EN-US">System.Runtime.Remoting.Activation</span><span style="FONT-FAMILY: 宋体">：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">object[] attrs = {new UrlAttribute("tcp://localhost:8086/Hello") };</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">ObjectHandle handle = Activator.CreateInstance(</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "RemoteHello", "Wrox.ProCSharp.Remoting.Hello", attrs);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">if (handle == null)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine("could not locate server");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> return;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Hello obj = (Hello)handle.Unwrap();</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Console.WriteLine(obj.Greeting("Christian"));</span></p>
<p class="MsoNormal"><span style="COLOR: black; FONT-FAMILY: 宋体">当然，对于客户激活的对象而言，也可以使用运算符</span><span lang="EN-US" style="COLOR: black">new</span><span style="COLOR: black; FONT-FAMILY: 宋体">替代</span><span lang="EN-US" style="COLOR: black">Activator</span><span style="COLOR: black; FONT-FAMILY: 宋体">类。如果使用运算符</span><span lang="EN-US" style="COLOR: black">new</span><span style="COLOR: black; FONT-FAMILY: 宋体">，就必须使用</span><span lang="EN-US" style="COLOR: black">RemotingConfiguration.RegisterActivatedClientType()</span><span style="COLOR: black; FONT-FAMILY: 宋体">注册客户激活的对象。在客户激活的对象体系中，运算符</span><span lang="EN-US" style="COLOR: black">new</span><span style="COLOR: black; FONT-FAMILY: 宋体">不但返回代理对象，也创建远程对象：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">RemotingConfiguration.RegisterActivatedClientType(typeof(Hello),</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "tcp://localhost:8086/HelloServer");</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Hello obj = new Hello();</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-US">4. </span><span style="FONT-FAMILY: 黑体">代理对象</span></h4>
<p class="MsoNormal"><span lang="EN-US">Activator.GetObject() </span><span style="FONT-FAMILY: 宋体">方法和</span><span lang="EN-US">Activator.CreateInstance()</span><span style="FONT-FAMILY: 宋体">方法都给客户返回一个代理对象。实际上得到两个代理对象：即透明代理对象和真实代理对象。透明代理对象看起来像远程对象，它执行远程对象的所有公共方法，这些方法调用真实代理对象的</span><span lang="EN-US">Invoke()</span><span style="FONT-FAMILY: 宋体">方法，传送包含方法调用的消息。在消息接收器的帮助下，</span><span lang="EN-US">RealProxy</span><span style="FONT-FAMILY: 宋体">把消息发送到信道中。</span></p>
<p class="MsoNormal"><span style="COLOR: black; FONT-FAMILY: 宋体">使用</span><span lang="EN-US" style="COLOR: black">RemotingServices.IsTransparentProxy()</span><span style="COLOR: black; FONT-FAMILY: 宋体">方法，可以检查对象是否真是透明代理对象。还可以通过</span><span lang="EN-US" style="COLOR: black">RemotingServices.GetRealProxy()</span><span style="COLOR: black; FONT-FAMILY: 宋体">获取真实代理对象。使用</span><span lang="EN-US" style="COLOR: black">Vasula Studio.NET</span><span style="COLOR: black; FONT-FAMILY: 宋体">调试器，很容易得到真实代理对象的所有属性：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">ChannelServices.RegisterChannel(new TCPChannel());</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Hello obj = (Hello)Activator.GetObject(typeof(Hello),</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "tcp://localhost:8086/Hi");</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">if (obj == null)</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine("could not locate server");</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> return;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">if (RemotingServices.IsTransparentProxy(obj))</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine("Using a transparent proxy");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> RealProxy proxy = RemotingServices.GetRealProxy(obj);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> // proxy.Invoke(message);</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 18pt"><span style="COLOR: black; FONT-FAMILY: 宋体">下面介绍代理对象的“可插入性”。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 18pt"><span style="FONT-FAMILY: 宋体">真实代理对象可以用定制的代理对象替代。定制的代理对象可以扩展基类</span><span lang="EN-US">System.Runtime. Remoting.RealProxy</span><span style="FONT-FAMILY: 宋体">。在定制代理对象的构造函数中接收远程对象的类型。调用</span><span lang="EN-US">RealProxy</span><span style="FONT-FAMILY: 宋体">的构造函数，可以创建真实代理对象和透明的代理对象。在构造函数中，在</span><span lang="EN-US">ChannelServices</span><span style="FONT-FAMILY: 宋体">类的帮助下创建消息接收器</span><span lang="EN-US">IChannelSender.CreateMessageSink()</span><span style="FONT-FAMILY: 宋体">，可以实现对已注册信道的访问。除了执行构造函数之外，定制的信道还必须重写</span><span lang="EN-US">Invoke()</span><span style="FONT-FAMILY: 宋体">方法。在</span><span lang="EN-US">Invoke()</span><span style="FONT-FAMILY: 宋体">中，可以对接收到的消息进行分析，然后把它们发送到消息接收器中。</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-US">5. </span><span style="FONT-FAMILY: 黑体">消息</span></h4>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">代理对象可以把消息发送到信道中。在服务器端分析了消息之后，方法调用就算完成了，因此，下面讨论消息。</span></p>
<p class="MsoNormal"><span lang="EN-US">.NET Framework</span><span style="FONT-FAMILY: 宋体">有一些消息类可以用于方法调用、响应以及返回消息等。所有的消息类都可以实现接口</span><span lang="EN-US">IMessage</span><span style="FONT-FAMILY: 宋体">，该接口只有一个属性</span><span lang="EN-US">Properties</span><span style="FONT-FAMILY: 宋体">。</span><span lang="EN-US">Properties</span><span style="FONT-FAMILY: 宋体">属性表示一个带有</span><span lang="EN-US">IDictionary</span><span style="FONT-FAMILY: 宋体">接口的字典，字典中包括对象的</span><span lang="EN-US">URI</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MethodName</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MethodSignature</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">TypeName</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Args</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">CallContext</span><span style="FONT-FAMILY: 宋体">等。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US">16-7</span><span style="FONT-FAMILY: 宋体">是消息类和接口的层次。发送给真实代理对象的消息是</span><span lang="EN-US">MethodCall</span><span style="FONT-FAMILY: 宋体">类型的对象。通过接口</span><span lang="EN-US">IMethodCallMessage </span><span style="FONT-FAMILY: 宋体">和</span> <span lang="EN-US">IMethodMessage</span><span style="FONT-FAMILY: 宋体">比通过接口</span><span lang="EN-US">IMessage</span><span style="FONT-FAMILY: 宋体">接口更容易实现对消息属性的访问。不必使用接口</span><span lang="EN-US">IDictionary</span><span style="FONT-FAMILY: 宋体">，仍可以直接访问方法名称、</span><span lang="EN-US">URI</span><span style="FONT-FAMILY: 宋体">和参数等内容。真实代理对象把</span><span lang="EN-US">ReturnMessage</span><span style="FONT-FAMILY: 宋体">返回给透明代理对象。</span></p>
<p align="center"><span lang="EN-US"><img height="214" src="16/image007.gif" width="561" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="COLOR: black; FONT-FAMILY: 宋体">图</span><span lang="EN-US" style="COLOR: black"> 16-7</span></p></div>
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<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165474.htm'><font color='red'>16.5.4 对象的激活</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165471.htm'>16.5.1 信道</a></div><div style='float:right;width:49%'>·<a href='100165472.htm'>16.5.2 格式标识符</a></div><div style='float:left;width:49%'>·<a href='100165473.htm'>16.5.3 ChannelServices和RemotingConfiguration</a></div><div style='float:right;width:49%'>·<a href='100165475.htm'>16.5.5 消息接收器</a></div><div style='float:left;width:49%'>·<a href='100165476.htm'>16.5.6 在远程方法中传递对象</a></div><div style='float:right;width:49%'>·<a href='100165477.htm'>16.5.7 生存期管理</a></div></div>
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