I am beginner to spring, ESP Inversion of control. I was puzzled understanding the difference between the following
<bean id="demo" class="Demo" lazy-init="false"/>
<bean id="demo" class="Demo" lazy-init="true"/>
<bean id="demo" class="Demo" lazy-init="default"/>
To my understanding : lazy-init=false creates the bean at the startup and lazy-init=true doesn't create a bean at the startup rather creates the bean upon request for a particular bean. Correct me here, If my interpretation is wrong.
what exactly the default behavior of lazy-init is? How would it instantiate?
This question is related to
spring
spring-ioc
lazy-init is the attribute of bean. The values of lazy-init can be true and false. If lazy-init is true, then that bean will be initialized when a request is made to bean. This bean will not be initialized when the spring container is initialized and if lazy-init is false then the bean will be initialized with the spring container initialization.
When we use lazy-init="default" as an attribute in element, the container picks up the value specified by default-lazy-init="true|false" attribute of element and uses it as lazy-init="true|false".
If default-lazy-init attribute is not present in element than lazy-init="default" in element will behave as if lazy-init-"false".
The lazy-init="default"
setting on a bean only refers to what is set by the default-lazy-init
attribute of the enclosing beans element. The implicit default value of default-lazy-init
is false
.
If there is no lazy-init
attribute specified on a bean, it's always eagerly instantiated.
For those coming here and are using Java config you can set the Bean to lazy-init using annotations like this:
In the configuration class:
@Configuration
// @Lazy - For all Beans to load lazily
public class AppConf {
@Bean
@Lazy
public Demo demo() {
return new Demo();
}
}
For component scanning and auto-wiring:
@Component
@Lazy
public class Demo {
....
....
}
@Component
public class B {
@Autowired
@Lazy // If this is not here, Demo will still get eagerly instantiated to satisfy this request.
private Demo demo;
.......
}
Source: Stackoverflow.com