In this short article, we’ll discuss Spring’s @Lazy annotation with an example.
By default, the Spring IoC container creates and initializes all singleton beans at the time of application startup. We can prevent this pre-initialization of a singleton bean by using the @Lazy annotation.
The @Lazy annotation may be used on any class directly or indirectly annotated with @Component or on methods annotated with @Bean.
YouTube Video - Spring @Lazy Annotation
In this example, we will use a Java-based configuration(using @Configuration and @Bean).
Spring @Lazy Annotation Example
Let's create an example to demonstrate using @Lazy annotation in a spring application.
Create a Simple Maven Project
Create a simple maven project using your favorite IDE and refer below section for packaging structure. If you are new to maven, read the article How to Create a Simple Maven Project.
Project Structure
The below diagram shows a project structure for your reference -Maven Dependency
Note that Spring framework 6 required Java 17 or later version:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>learn-spring-framework</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>17</maven.compiler.source>
<maven.compiler.target>17</maven.compiler.target>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>6.0.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>6.0.6</version>
</dependency>
</dependencies>
</project>
Create Spring Beans - FirstBean and SecondBean
FirstBean.javapackage net.javaguides.spring.lazy;
public class FirstBean {
public FirstBean() {
System.out.println("Inside FirstBean Constuctor");
}
public void test() {
System.out.println("Method of FirstBean Class");
}
}
package net.javaguides.spring.lazy;
public class SecondBean {
public SecondBean() {
System.out.println("Inside SecondBean Constuctor");
}
public void test() {
System.out.println("Method of SecondBean Class");
}
}
Java-Based Configuration - AppConfig.java
Declare the above beans in java based configuration class.package net.javaguides.spring.lazy;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Lazy;
@Configuration
public class AppConfig {
@Lazy(value = true)
@Bean
public FirstBean firstBean() {
return new FirstBean();
}
@Bean
public SecondBean secondBean() {
return new SecondBean();
}
}
Running Spring Application - Application.java
Let's create a main class and run an application.package net.javaguides.spring.lazy;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Application {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
FirstBean firstBean = context.getBean(FirstBean.class);
firstBean.test();
context.close();
}
}
Inside SecondBean Constuctor
Inside FirstBean Constuctor
Method of FirstBean Class
As we can see, bean secondBean is initialized by the Spring container while bean firstBean is initialized explicitly.
The source code of this article is available on my GitHub repository https://github.com/RameshMF/spring-core-tutorial
Related Spring and Spring Boot Annotations
- Spring Boot @Bean Annotation Example
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- Spring @Autowired Annotation with Example
- Spring @Bean Annotation with Example
- Spring @Configuration Annotation with Example
- Spring @PropertySource Annotation with Example
- Spring @Import Annotation with Example
- Spring @ImportResource Annotation Example
- Spring - @Lazy Annotation Example
- Spring - @Primary Annotation Example
- Spring @PostConstruct and @PreDestroy Example
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- The Spring @Controller and @RestController Annotations
- Spring Boot @Component, @Controller, @Repository and @Service
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- Spring Boot @EnableAutoConfiguration Annotation with Example
- Spring Boot @SpringBootApplication Annotation with Example
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