The default behavior of ApplicationContext implementation is to instantiate all singleton beans in advance (that is, dependency injection) at startup. Early instantiation means that as part of the initialization process, the ApplicationContext instance creates and configures all singleton beans. Usually this isGood thing, because any errors in the configuration will be discovered immediately (otherwise it may take several hours or even days).
<bean class=""> The default setting of this bean is:
<bean class="" lazy-init="false"> lazy-init="false" Instant loading, indicating that the instantiation is immediately performed when spring starts.
(Lazy-init setting only works on beans with singleton scop attribute)
Sometimes this default processing maynoWhat you want. If you don't want a singleton bean to be instantiated in the ApplicationContext implementation at initialization, you can set the bean to be deferred instantiated.
<bean class="" lazy-init="true">, lazy-init="true"> Lazy loading, the bean set to lazy willWon'tIt is instantiated in advance when the ApplicationContext starts, but is instantiated when the bean is requested from the container through the getBean.
If a bean1 that is loaded immediately refers to a lazy loaded bean2, then bean1 is instantiated when the container is started, and bean2 is also instantiated because it is referenced by bean1. This situation also complies with the rule that the delayed bean is instantiated on the first call.
By using on the <beans/> element in the container hierarchy'default-lazy-init'Properties to control delayed initialization is also possible. As shown in the following configuration:
<beans default-lazy-init="true"><!-- no beans will be eagerly pre-instantiated... --></beans>
If the scope property of a bean is scope="pototype", even if lazy-init="false" is set, the bean is not instantiated when the container starts, but the getBean method is called instantiated.
Also explain:
The .init-method property specifies the method executed during initialization, and the distance-method property specifies the method executed during bean destruction.