Spring中有5种bean的范围：
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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：
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public
class
CustomerService
{
String message;
public
String getMessage() {
return
message;
}
public
void
setMessage(String message) {
this
.message = message;
}
}
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1. Singleton example
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<beans xmlns=
"http://www.springframework.org/schema/beans"
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>
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运行：
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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());
}
}
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输出为：
Message : Message by custA Message : Message by custA
2. Prototype example
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
<
bean
id="customerService" class="com.mkyong.customer.services.CustomerService"
scope="prototype"/>
</
beans
>
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运行输出为：
Message : Message by custA Message : null
也可以使用注解来做这些事情：
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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;
}
}
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<beans xmlns=
"http://www.springframework.org/schema/beans"
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>
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