EnterLib ObjectBuild vs Castle WindsorContainer, part 1
Posted on 2006-08-15 14:35 idior 阅读(6537) 评论(16) 编辑 收藏 举报1: public interface IEmailSender
2: {
3: void Send(String from, String to, String message);
4: }
5:
6: public interface ITemplateEngine
7: {
8: String Process(String templateName);
9: }
10:
11: public interface INewsletterService
12: {
13: void Dispatch(String from, String[] targets, String message);
14: }
15:
16: public class SmtpEmailSender : IEmailSender
17: {
18: private String _host;
19: private int _port;
20:
21: public SmtpEmailSender(String host, int port)
22: {
23: _host = host;
24: _port = port;
25: }
26:
27: public virtual void Send(String from, String to, String message)
28: {
29: Console.WriteLine("Sending e-mail from {0} to {1} with '{2}'",
30: from, to, message );
31: }
32: }
33:
34: public class NVelocityTemplateEngine : ITemplateEngine
35: {
36: public virtual String Process(String templateName)
37: {
38: return "Some template content";
39: }
40: }
41:
42: public class SimpleNewsletterService : INewsletterService
43: {
44: private IEmailSender _sender;
45: private ITemplateEngine _templateEngine;
46:
47: public SimpleNewsletterService
48: (IEmailSender sender, ITemplateEngine templateEngine)
49: {
50: _sender = sender;
51: _templateEngine = templateEngine;
52: }
53:
54: public void Dispatch(String from, String[] targets, String message)
55: {
56: String msg = _templateEngine.Process(message);
57:
58: foreach(String target in targets)
59: {
60: _sender.Send(from, target, msg);
61: }
62: }
63:
64: }
Ioc的作用就是能够利用容器自动的构建出一个SimpleNewsletterService对象，而不是由用户直接的创建并传递其参数，这样就可以进一步降低对象与对象之间耦合程度，从而方便的替换其实现。在上例中将采用构造器设值的方式，来实现对象依赖关系的注入。下面给出Castle的实现方式：
BasicUsage.xml
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<components>
<component id="smtpemailsender">
<parameters>
<host>localhost</host>
<port>110</port>
</parameters>
</component>
</components>
</configuration>
1: public static void Main()
2: {
3: IWindsorContainer container =
4: new WindsorContainer( new XmlInterpreter("../BasicUsage.xml") );
5:
6: container.AddComponent( "newsletter",
7: typeof(INewsletterService), typeof(SimpleNewsletterService) );
8: container.AddComponent( "smtpemailsender",
9: typeof(IEmailSender), typeof(SmtpEmailSender) );
10: container.AddComponent( "templateengine",
11: typeof(ITemplateEngine), typeof(NVelocityTemplateEngine) );
12:
13: String[] friendsList = new String[] { "john", "steve", "david" };
14:
15: // Ok, start the show
16:
17: INewsletterService service =
18: (INewsletterService) container["newsletter"];
19: service.Dispatch("hammett at gmail dot com",
20: friendsList, "merryxmas");
21: }
不断向容器中加入各种类型的对象，加入过程中容器自动建立起它们之间的依赖关系，最后当我们从容器取出对象的时候，就是已经配置好依赖关系的对象。以上就是Castle的工作模式，不过Castle中的配置过程过于透明，在你完全意料不到的情况下，对象的依赖关系就按照对象被注入容器的先后顺序被设定了。非常的自动，非常的透明带来的就是某些时候的莫名奇妙。
再来看看ObjectBuild的实现方式，首先你需要通过属性(Attibute)或者配置文件的方式显式的设定依赖关系：
42: public class SimpleNewsletterService : INewsletterService
43: {
44: private IEmailSender _sender;
45: private ITemplateEngine _templateEngine;
46:
47: public SimpleNewsletterService(
48: [Dependency(CreateType = typeof(SmtpEmailSender))]
49: IEmailSender sender,
50: [Dependency(CreateType = typeof(NVelocityTemplateEngine))]
51: ITemplateEngine templateEngine)
52: {
53: _sender = sender;
54: _templateEngine = templateEngine;
55: }
56:
57: public void Dispatch(String from, String[] targets, String message)
58: {
59: String msg = _templateEngine.Process(message);
60:
61: foreach(String target in targets)
62: {
63: _sender.Send(from, target, msg);
64: }
65: }
66:
67: }
然后再利用Build直接的构造出对象
public static void Main(string[] args)
{
string config = string.Format(
@"<object-builder-config xmlns='pag-object-builder'>
<build-rules>
<build-rule type='{0}' mode='Singleton'>
<mapped-type type='{1}'/>
<constructor-params>
<value-param type='System.String'>localhost</value-param>
<value-param type='System.Int32'>110</value-param>
</constructor-params>
</build-rule>
</build-rules>
</object-builder-config>", FullNameIEmailSender, FullNameSmtpEmailSender);
Builder builder = new Builder(ObjectBuilderXmlConfig.FromXml(config));
Locator locator = CreateLocator();
INewsletterService newsletterService =
builder.BuildUp<SimpleNewsletterService>(locator, null, null);
String[] friendsList = new String[] { "john", "steve", "david" };
// Ok, start the show
newsletterService.Dispatch("hammett at gmail dot com",
friendsList, "merryxmas");
}
从以上我们可以看出
1. ObjectBuild和Sping类似，需要显式指定依赖关系，不过多出通过Attribute来指定的方式，而Castle则依赖于特定的对象注入顺序。可以说各有优缺点，但是我prefer前者，安全第一。(Castle也提供了在配置文件中显式指定的方式。)
2. ObjectBuild支持直接创建临时对象，而不注入容器。(注意在上面的代码中我们仅仅BuildUp了SimpleNewsletterService，而没有象Castle那样还要将SimpleNewsletterService所依赖的对象也注入容器。)其实在OB中你可以选择是否将对象注入容器，通常情况下Singleton类型的对象才被注入容器。
3. 相对与Castle容器的概念，ObjectBuild如同它的名字所示，更象是一个构建器，你可以通过它来构建任意的对象，这些对象可能会被注入容器，也可能仅仅是一个临时对象，不过在对象的创建过程中你可以加入很多的控制，让它更符合你的需求。
4. 相对而言Castle Ioc的使用更加简洁，而ObjectBuild更加复杂一些(其实比较它们构建对象所需要的语句，OB需要的更少，只是OB的API还不够简洁，需要再做些包装)，不过ObjectBuild的定制扩展能力也是相当强大，比如以上通过配置文件和属性(Attribute)结合的配置方式，完全可以通过OB中提供的API搞定，下面就是采用全编程方式的实现：
public static void Main()
{
Builder builder = new Builder();
Locator locator = CreateLocator();
builder.Policies.SetDefault<ISingletonPolicy>(new SingletonPolicy(true));
ConstructorPolicy policy = new ConstructorPolicy();
policy.AddParameter(new ValueParameter<string>("localhost"));
policy.AddParameter(new ValueParameter<int>(110));
builder.Policies.Set<ICreationPolicy>
(policy, typeof(SmtpEmailSender), null);
builder.Policies.Set<ITypeMappingPolicy>
(new TypeMappingPolicy(typeof(SmtpEmailSender), null),
typeof(IEmailSender), null);
builder.Policies.Set<ITypeMappingPolicy>
(new TypeMappingPolicy(typeof(NVelocityTemplateEngine), null),
typeof(ITemplateEngine), null);
ConstructorPolicy policy2 = new ConstructorPolicy();
policy2.AddParameter(new CreationParameter(typeof(IEmailSender)));
policy2.AddParameter(new CreationParameter(typeof(ITemplateEngine)));
builder.Policies.Set<ICreationPolicy>
(policy2,typeof(SimpleNewsletterService),null);
INewsletterService newsletterService =
builder.BuildUp<SimpleNewsletterService>(locator, null, null);
String[] friendsList = new String[] { "john", "steve", "david" };
// Ok, start the show
newsletterService.Dispatch("hammett at gmail dot com",
friendsList, "merryxmas");
}
5. Castle Ioc和ObjectBuild都支持属性设值(Property Setter)的注入方式，在此不再举例。
