spring在启动的时候,会默认加载会默认加载整个对象实例图,从初始化ACTION配置、到 service配置到dao配置、乃至到数据库连接、事务等等。这样可以减少web服务器在运行时的负担,但是对于开发者来说无疑是效率极低的一个设置了。
spring提供了default-lazy-init属性,其配置形式如下,applicationContext.xml中:
<beans default-lazy-init ="true"> </beans>
我用以前一个office项目测试了下,因为office的spring文件很多,我就配置了下,启动时间减少60%左右。
1.lazy-init
<beans> <bean id="service1" type="bean路径" lazy-init="true"/> <bean id="service2" type="bean路径" lazy-init="false"> <property name="service1" ref="service1"/> </bean> </beans>
以上两个bean,一个lazy-init属性为true,一个为false,由什么区别呢
当 IoC容器启动时,service2会实例化,而service1则不会;但是但容器实例化service2时,service1也被实例化了,为什么呢,因为service2需要它。也就是说lazy-init="true"的bean,IoC容器启动时不会实例化该bean,只有当容器需要用到时才实例化它。lazy-init有利于容器效率,对于不需要的bean可以先不管。
2.abstract
<bean id="baseTxService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean" abstract="true"> </bean>
bean abstract="true"时,该bean不会被实例化,上面的bean是个模板
在同一个文件中<bean />里面设置的优先级大于<beans />里设置的优先级:
<beans /> <bean /> immediately <beans /> <bean lazy-init="true" /> lazy <beans /> <bean lazy-init="false"/> immediately <beans default-lazy-init="true"/> <bean /> lazy <beans default-lazy-init="true"/> <bean lazy-init="true" /> lazy <beans default-lazy-init="true"/> <bean lazy-init="false" /> immediately <beans default-lazy-init="false"/> <bean /> immediately <beans default-lazy-init="false"/> <bean lazy-init="true" /> lazy <beans default-lazy-init="false"/> <bean lazy-init="false" /> immediately
如果在一个spring配置文件中引入另外的配置文件,如:<import resource="classpath:beans.xml"/>
则以被引入文件(beans.xml)中设置的<beans />里的设置为准,与引入文件中的设置无关。
<bean id="testInit" lazy-init="true" init-method="init" class="com.test.Test"> </bean>
One thing to understand about lazy-initialization is that even though a bean definition may be marked up as being lazy-initialized, if the lazy-initialized bean is the dependency of a singleton bean that is not lazy-initialized, when the ApplicationContext is eagerly pre-instantiating the singleton, it will have to satisfy all of the singletons dependencies, one of which will be the lazy-initialized bean! So don't be confused if the IoC container creates one of the beans that you have explicitly configured as lazy-initialized at startup; all that means is that the lazy-initialized bean is being injected into a non-lazy-initialized singleton bean elsewhere.
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