JAVA EE: Spring Bean Life Cycle - BeanFactoryAware Interface | Spring Tutorial

Friday, 24 August 2018

Spring Bean Life Cycle - BeanFactoryAware Interface | Spring Tutorial | Spring Framework

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What is the BeanFactoryAware Interface?

In Spring, the BeanFactoryAware interface is a marker-like Aware interface that allows a bean to obtain a reference to the Spring IoC container's BeanFactory that created it. By implementing this interface, your bean gains direct access to container services, such as programmatically fetching other beans or inspecting bean metadata.

How Does BeanFactoryAware Work in the Lifecycle?

During the bean creation phase, the Spring container executes these steps:

Instantiates the bean and injects all configured dependencies.
Checks whether the bean implements BeanFactoryAware.
Invokes the callback method setBeanFactory(BeanFactory beanFactory), passing the container instance to the bean.
The bean can then store this reference and use it at runtime to lookup dependencies dynamically.

Example Implementation

public class BeanFactoryAwareImpl implements BeanFactoryAware {
    private BeanFactory beanFactory;

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }

    public void displayEmployeeDetails() {
        Employee emp = beanFactory.getBean("employee", Employee.class);
        System.out.println("Employee: " + emp);
        System.out.println("Is Singleton: " + beanFactory.isSingleton("employee"));
    }
}

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Spring Bean Life Cycle - BeanFactoryAware Interface | Spring Tutorial | Spring Framework

pom.xml

<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%20http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.2.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

Employee.java

package com.ram.model;

/**
 * Spring bean
 */

public class Employee

{

    private String name;

    public void setName(String name)

    {

        this.name = name;

    }

    @Override

    public String toString()

    {

        return "Employee [name=" + name + "]";

    }

}

BeanFactoryAwareImpl.java

package com.ram.factoryaware;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.BeanFactoryAware;

import com.ram.model.Employee;

public class BeanFactoryAwareImpl implements BeanFactoryAware

{

    private BeanFactory beanFactory;

    public void setBeanFactory(BeanFactory beanFactory) throws BeansException

    {

        System.out.println(

                "setBeanFactory method called by the Spring Container");

        this.beanFactory = beanFactory;

    }

    public void displayEmployeeDetails()

    {

        Employee employee = beanFactory.getBean("employee", Employee.class);

        System.out.println(

                "Got employee object from the BeanFactory(Spring Container) = "

                        + employee);

        System.out.println("is employee object Singleton? = "

                + beanFactory.isSingleton("employee"));

    }

}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <bean id="employee" class="com.ram.model.Employee">

        <property name="name" value="Peter" />

    </bean>

    <bean id="beanFactoryAware" class="com.ram.factoryaware.BeanFactoryAwareImpl"/>

</beans>

App.java

package com.ram.core;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.factoryaware.BeanFactoryAwareImpl;

public class App

{

    public static void main(String[] args)

    {

        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        BeanFactoryAwareImpl beanFactoryAwareImpl = applicationContext

                .getBean("beanFactoryAware", BeanFactoryAwareImpl.class);

        beanFactoryAwareImpl.displayEmployeeDetails();

        applicationContext.close();

    }

}

Output

Aug 11, 2018 11:46:52 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Sat Aug 11 11:46:52 IST 2018]; root of context hierarchy

Aug 11, 2018 11:46:52 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

setBeanFactory method called by the Spring Container

Got employee object from the BeanFactory(Spring Container) = Employee [name=Peter]

is employee object Singleton? = true

Aug 11, 2018 11:46:53 AM org.springframework.context.support.AbstractApplicationContext doClose

INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Sat Aug 11 11:46:52 IST 2018]; root of context hierarchy