spring Spring Lazy Initialization Example of Lazy Init in Spring


Example

The @Lazy allow us to instruct the IOC container to delay the initialization of a bean. By default, beans are instantiated as soon as the IOC container is created, The @Lazy allow us to change this instantiation process.

lazy-init in spring is the attribute of bean tag. The values of lazy-init are 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. If lazy-init is false then the bean will be initialized with the spring container initialization and this is the default behavior.

app-conf.xml

<beans xmlns="http://www.springframework.org/schema/beans" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd">
 
<bean id="testA" class="com.concretepage.A"/>
<bean id="testB" class="com.concretepage.B" lazy-init="true"/>

A.java

package com.concretepage;
public class A {
public A(){
    System.out.println("Bean A is initialized");
   }
}

B.java

package com.concretepage;
public class B {
public B(){
    System.out.println("Bean B is initialized");
   }
} 

SpringTest.java

package com.concretepage;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest {
public static void main(String[] args) {
     ApplicationContext context = new ClassPathXmlApplicationContext("app-conf.xml");
     System.out.println("Feth bean B.");
     context.getBean("testB");
   }
}

Output

Bean A is initialized
Feth bean B.
Bean B is initialized