blocks|key|1285399|text|普通的polimorphysm有什么问题？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1285400|定义一个接口并在ServicesDao和ServicesBO中实现它|offset|length|style|CODE|1285401|public+interface+UserProvider{

++++List<users>+getUsers();
}|code-block|syntax|javascript|1285402|然后你就可以|1285403|++UserProvider+services+=+(UserProvider)appContext.getBean(beanName);

++List<users>+list+=+services.getUsers();+

++for+(users+user:+list){+/*+do+stuff+with+user*/}|1285404|entityMap^0|0|8|B|K|A|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@$D|U|E|V|F|G]|$D|W|E|X|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|Q|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|R|$]]

Whats wrong with plain polimorphysm?

Define an interface and implement it in the <code>ServicesDao</code> and <code>ServicesBO</code>

<pre><code>public interface UserProvider{

 List&lt;users&gt; getUsers();
}
</code></pre>

Then you can

<pre><code> UserProvider services = (UserProvider)appContext.getBean(beanName);

 List&lt;users&gt; list = services.getUsers(); 

 for (users user: list){ /* do stuff with user*/}
</code></pre>

blocks|key|1285408|text|解决这个问题的简单方法是让两个服务对象都实现一个公共接口。类似于：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1285409|public+interface+UserSource+{
++++List<users>+getUsers();
}|code-block|syntax|javascript|1285410|然后将ServicesBO和ServicesDAO标记为实现此接口，这允许您执行以下操作：|offset|length|style|CODE|1285411|private+void+getFieldProvider(String+providerName){
++++UserSource+services+=+(UserSource)appContext.getBean(providerName);
++++List<users>+list+=+services.getUsers();

++++for+(users+user:+list)
++++++++System.out.println(providerName+%2B+":+"+%2B+user.getName());
}|1285412|更复杂的方法是使用反射，它允许您在不需要提供服务对象共享的接口的情况下执行此操作。例如，您可以执行以下操作：|1285413|private+void+getFieldProvider(String+providerName){
++++Object+services+=+appContext.getBean(providerName);
++++List<users>+list+=+Collections.emptyList();
++++try+{
++++++++Method+method+=+services.getClass().getMethod("getUsers");
++++++++list+=+(List<users>)method.invoke(services);
++++}
++++catch+(Exception+e)+{
++++++++e.printStackTrace();
++++}

++++for+(users+user:+list)
++++++++System.out.println(providerName+%2B+":+"+%2B+user.getName())
}|1285414|entityMap^0|0|0|3|A|E|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

The simple way to solve this is to have both of your service objects implement a common interface. Something like:

<pre><code>public interface UserSource {
 List&lt;users&gt; getUsers();
}
</code></pre>

Then you mark <code>ServicesBO</code> and <code>ServicesDAO</code> as implementing this interface, which allows you to do:

<pre><code>private void getFieldProvider(String providerName){
 UserSource services = (UserSource)appContext.getBean(providerName);
 List&lt;users&gt; list = services.getUsers();

 for (users user: list)
 System.out.println(providerName + ": " + user.getName());
}
</code></pre>

The more complex way is to use Reflection, which allows you to do this without needing to provide an interface for the service objects to share. For example, you can do:

<pre><code>private void getFieldProvider(String providerName){
 Object services = appContext.getBean(providerName);
 List&lt;users&gt; list = Collections.emptyList();
 try {
 Method method = services.getClass().getMethod("getUsers");
 list = (List&lt;users&gt;)method.invoke(services);
 }
 catch (Exception e) {
 e.printStackTrace();
 }

 for (users user: list)
 System.out.println(providerName + ": " + user.getName())
}
</code></pre>

blocks|key|5709343|text|如果没有ServicesDao和ServicesBO都实现的公共接口，您将无法在没有反射的情况下调用getUsers。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5709344|所以假设你有一个通用的接口：|5709345|public+interface+UserProvider+{
++++List<User>+getUsers();
}|code-block|syntax|javascript|5709346|您可以按如下方式定义该方法：|5709347|private+void+printUsers(String+beanName)+{
++++UserProvider+provider+=+appContext.getBean(beanName,+UserProvider.class);
++++List<User>+users+=+provider.getUsers();

++++for+(User+user+:+users)
++++++++System.out.println("DAO:"+%2B+user.getName());
}|5709348|还有一些其他的东西：|5709349|5709350|通常类名以大写开头(Users而不是users)|unordered-list-item|5709351|类名可能应该是User因为getName方法表明类只包含一个用户|5709352|我认为使用spring注入bean比从应用程序上下文中查找它们更好。|5709353|5709354|希望这能有所帮助。|5709355|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|13|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|14|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|15|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|16|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|17|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|18|8|@]|9|@]|A|$]]|$1|S|3|T|5|R|7|19|8|@]|9|@]|A|$]]|$1|U|3|V|5|R|7|1A|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]|$1|X|3|Y|5|6|7|1C|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|10|$]]

Without a common interface that both ServicesDao and ServicesBO implement, you won't be able to call getUsers without reflection. 

So assuming that you've got a common interface:

<pre><code>public interface UserProvider {
 List&lt;User&gt; getUsers();
}
</code></pre>

You can define the method as follows:

<pre><code>private void printUsers(String beanName) {
 UserProvider provider = appContext.getBean(beanName, UserProvider.class);
 List&lt;User&gt; users = provider.getUsers();

 for (User user : users)
 System.out.println("DAO:" + user.getName());
}
</code></pre>

A couple of other things:

<ul>
<li>usually class names start with uppercase (Users not users)</li>
<li>class name should probably be User as the getName method suggests that the class only holds a single user</li>
<li>I'd consider it better practice to use spring to inject beans rather than looking them up from the application context. </li>
</ul>

Hope that helps.

I'd like to merge this two methods using generics, the only difference are the casting classes "ServicesBO" and "ServicesDAO". The name of the bean can be passed as a string parameter. Is it possible to merge them using generics for the casting classes?

<pre><code>private void getFieldBO(){
 ServicesBO services = (ServicesBO)appContext.getBean("ServicesBo");
 List&lt;users&gt; list = services.getUsers();

 for (users user: list)
 System.out.println("BO: " + user.getName());
}

private void getFieldDAO(){
 ServicesDAO services = (ServicesDAO)appContext.getBean("ServicesDAO");
 List&lt;users&gt; list = services.getUsers();

 for (users user: list)
 System.out.println("DAO: " + user.getName());
}
</code></pre>

Thanks in Advance
Chuck.

Generics with Spring

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想使用泛型合并这两个方法，唯一的区别是造型类"ServicesBO“和"ServicesDAO”。bean的名称可以作为字符串参数传递。是否可以使用类型转换类的泛型来合并它们？private void getFieldBO(){    ServicesBO services = (ServicesBO)appCont...

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