JAVA EE: Spring Bean Life Cycle - Spring InitializingBean and DisposableBean

Friday, 17 August 2018

Spring Bean Life Cycle - Spring InitializingBean and DisposableBean | Spring Tutorial

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What are InitializingBean and DisposableBean?

In the Spring Framework, managing the creation and destruction phases of your objects is essential for setup operations and clean resource management. Spring provides two core programmatic callback interfaces: InitializingBean and DisposableBean.

InitializingBean: Provides the afterPropertiesSet() method, which the Spring container invokes immediately after all bean properties are set and dependencies are injected.
DisposableBean: Provides the destroy() method, which is invoked when the Spring container shuts down and the bean instance is being destroyed.

How Does It Work?

By directly implementing these interfaces in your bean class, Spring automatically detects and invokes the lifecycle hooks without needing extra configuration:

Automatic Invocation: Spring executes afterPropertiesSet() after initialization and destroy() on container shutdown.
Programmatic Approach: Useful when you want explicit contract enforcement for initialization and cleanup logic directly inside your Java class.

Sample Implementation Code

Here is an example of implementing both interfaces in a Spring bean:

public class DatabaseService implements InitializingBean, DisposableBean {

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("Init: Database connection initialized.");
    }

    @Override
    public void destroy() throws Exception {
        System.out.println("Clean up: Database connection closed.");
    }
}

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Spring Bean Life Cycle - Spring InitializingBean and DisposableBean | Spring Tutorial

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;

import org.springframework.beans.factory.DisposableBean;

import org.springframework.beans.factory.InitializingBean;

public class Employee implements InitializingBean, DisposableBean

{

    private int id;

    private String name;

    public int getId()

    {

        return id;

    }

    public void setId(int id)

    {

        this.id = id;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

    public void afterPropertiesSet() throws Exception

    {

        System.out.println("inside afterPropertiesSet().  ");

    }

    public void destroy() throws Exception

    {

        System.out.println("Inside destroy(), Performed clean up tasks.");

    }

    @Override

    public String toString()

    {

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

    }

}

applicationContext.xml

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

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

    xmlns:context="http://www.springframework.org/schema/context"

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

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

    http://www.springframework.org/schema/context

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

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

        <property name="id" value="100"></property>

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

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ConfigurableApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.model.Employee;

public class App

{

    public static void main(String[] args)

    {

        ConfigurableApplicationContext  context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        System.out.println("---------------------------------------");

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

        System.out.println(

                "Got employee object from the ApplicationContext(Spring Container)");

        System.out.println(employee);

        context.close();

    }

}

Output

Aug 06, 2018 10:35:53 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Mon Aug 06 10:35:53 IST 2018]; root of context hierarchy

Aug 06, 2018 10:35:53 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

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

inside afterPropertiesSet(). 

---------------------------------------

Got employee object from the ApplicationContext(Spring Container)

Employee [id=100, name=Peter]

Aug 06, 2018 10:35:54 AM org.springframework.context.support.AbstractApplicationContext doClose

INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Mon Aug 06 10:35:53 IST 2018]; root of context hierarchy

Inside destroy(), Performed clean up tasks.