Spring中bean的范围-白红宇

Spring中有5种bean的范围：

5 types of bean scopes supported :

singleton – Return a single bean instance per Spring IoC container 这个范围也是默认的

prototype – Return a new bean instance each time when requested

request – Return a single bean instance per HTTP request. *

session – Return a single bean instance per HTTP session. *

globalSession – Return a single bean instance per global HTTP session. *

P.S * means only valid in the context of a web-aware Spring ApplicationContext

我们看个关于singleton and prototype.的例子：

                         
public
class
CustomerService
{ 
    
String message;
 
public
String getMessage() { 
        
return
message;
    
}
 
public
void
setMessage(String message) { 
        
this
.message = message;
    
}
}

1. Singleton example

                         
<beans xmlns=
""
    
xmlns:xsi=
""
    
xsi:schemaLocation="http:
//www.springframework.org/schema/beans
    
http:
//www.springframework.org/schema/beans/spring-beans-2.5.xsd">
 
       
<bean id=
"customerService"
            
class
=
"com.mkyong.customer.services.CustomerService"
/>
 
</beans>
        
      

　　运行：

                         
public
class
App
{ 
    
public
static
void
main( String[] args )
    
{ 
        
ApplicationContext context =
         
new
ClassPathXmlApplicationContext(
new
String[] { 
"Spring-Customer.xml"
});
 
        
CustomerService custA = (CustomerService)context.getBean(
"customerService"
);
        
custA.setMessage(
"Message by custA"
);
        
System.out.println(
"Message : "
+ custA.getMessage());
 
        
//retrieve it again
        
CustomerService custB = (CustomerService)context.getBean(
"customerService"
);
        
System.out.println(
"Message : "
+ custB.getMessage());
    
}
}
        
      

　　输出为：

Message : Message by custAMessage : Message by custA

2. Prototype example

                         
<
beans
xmlns=""
    
xmlns:xsi=""
    
xsi:schemaLocation="
    
">
 
<
bean
id="customerService" class="com.mkyong.customer.services.CustomerService"
         
scope="prototype"/>
 
</
beans
>

　　运行输出为：

Message : Message by custAMessage : null 也可以使用注解来做这些事情：

                         
package
com.mkyong.customer.services;
 
import
org.springframework.context.annotation.Scope;
import
org.springframework.stereotype.Service;
 
@Service
@Scope
(
"prototype"
)
public
class
CustomerService
{ 
    
String message;
 
    
public
String getMessage() { 
        
return
message;
    
}
 
    
public
void
setMessage(String message) { 
        
this
.message = message;
    
}
}
        
      

                         
<beans xmlns=
""
    
xmlns:xsi=
""
    
xmlns:context=
""
    
xsi:schemaLocation="http:
//www.springframework.org/schema/beans
    
http:
//www.springframework.org/schema/beans/spring-beans-2.5.xsd
    
http:
//www.springframework.org/schema/context
    
http:
//www.springframework.org/schema/context/spring-context-2.5.xsd">
 
       
<context:component-scan base-
package
=
"com.mkyong.customer"
/>
 
</beans>
        
      