原文：http://www.tuicool.com/articles/RzIvAj

spring生成物件預設是單例的。通過scope屬性可以更改為多例。

<bean id="user" class="modle.User" scope="prototype">
</bean>

User類呼叫一個service， 這個service又呼叫一個tool。

有時我們希望User是多例的，service是單例的，而tool又是多例的。

很自然地想法是配置檔案這些寫

<bean id="user" class="modle.User" scope
 
="prototype">
<property name="service" ref="userservice"></property>
</bean>

<bean id="userservice" class="service.userService" >
<property name="tool" ref="tool"></property>
</bean>

<bean id="tool" class="service.ToolImpl" scope="prototype"></bean>
 

但是這種寫法是錯誤的！ 不能使用spring的自動注入！

由於service是單例的，所以這種方法的結果是：User多例，service和tool都是單例。（為什麼？）

官網文件：

4.5.3 Singleton beans with prototype-bean dependencies

When you use singleton-scoped beans with dependencies on prototype beans, be aware that dependencies are resolved at instantiation time. Thus if you dependency-inject a prototype
 
-scoped bean into a singleton-scoped bean, a new prototype bean is instantiated and then dependency-injected into the singleton bean. The prototype instance is the sole instance that is ever supplied to the singleton-scoped bean.

However, suppose you want the singleton-scoped bean to acquire a new instance of the prototype-scoped bean repeatedly at runtime. You cannot dependency-inject a prototype-scoped bean into your singleton bean, because that injection occurs only once, when the Spring container is instantiating the singleton bean and resolving and injecting its dependencies. If you need a new instance of a prototype bean at runtime more than once, see Section 4.4.6, “Method injection”

正確的寫法是，是每次呼叫tool時都生成一個新的tool物件。但是我們又不能手動new一個，要藉助BeanFactory

public class User {

private userService service;
private int age;
private Date date;
private String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public userService getService() {
return service;
}
public void setService(userService service) {
this.service = service;
}

}

由於不使用spring的自動注入，set方法要去掉！

public class userService implements BeanFactoryAware{

private Tool tool;
private BeanFactory factory;
public void service(){
this.tool = (Tool)factory.getBean("tool");
System.out.println(this+":service");
tool.work();
}
public Tool getTool() {

return tool;
}
//	public void setTool(Tool tool) {
//		
//		this.tool = (Tool)factory.getBean("tool");
//	}
public void setBeanFactory(BeanFactory f) throws BeansException {
factory = f;
}

}

<bean id="user" class="modle.User" scope="prototype">
<property name="service" ref="userservice"></property>
</bean>

<bean id="userservice" class="service.userService" >
</bean>

<bean id="tool" class="service.ToolImpl" scope="prototype"></bean>

public interface Tool {
public void work();
}

public class ToolImpl implements Tool{

public void work() {
System.out.println(this+":Tool Work");
}

}

public class Test {
public static void main(String[] args) {
ClassPathResource res = new ClassPathResource("applicationContext.xml");
XmlBeanFactory factory = new XmlBeanFactory(res);
User user = (User)factory.getBean("user");
User user2 =  (User)factory.getBean("user");

System.out.println(user);
user.getService().service();
System.out.println();
System.out.println(user2);
user2.getService().service();
}
}

modle.User@42552c
service.userService@19e15c:service
service.ToolImpl@11a75a2:Tool Work

modle.User@210b5b
service.userService@19e15c:service
service.ToolImpl@170888e:Tool Work