Spring @Lazy Annotation Example

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 application startup. However, we can prevent this pre-initialization by using the @Lazy annotation.

The @Lazy annotation may be used in any class directly or indirectly annotated with @Component or in methods annotated with @Bean.

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 favourite IDE. Refer to the section below for the 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 requires Java 17 or later version:

        
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
    <dependency>
        <groupId>org.springframework
        <artifactId>spring-core
        <version>6.1.8
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
    <dependency>
        <groupId>org.springframework
        <artifactId>spring-context
        <version>6.1.8
    </dependency>

Create Spring Beans - FirstBean and SecondBean

FirstBean.java

package 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");
    }
}

SecondBean.java

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 the 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();
        }
    }

Output:

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.