In the other example, How do I initialize and destroy beans in Spring? you can see how to initialize and destroy a bean using the Spring configuration init-method and destroy-method.
In the following example you’ll see how to achieve the same thing using the Spring API. In this case our class need to implements the InitializingBean and DisposableBean. These interfaces are located under the org.springframework.beans.factory package.
The InitializingBean interface requires us to implements the afterPropertiesSet() method. This method will be the init method of our bean. The destroy() method which is a contract defined in the DisposableBean interface is where we’ll place the clean-up logic of our bean.
The drawback of using this approach is that our classes will be required to use the Spring API. If you want to use the class outside the Spring container using the other approach mentioned above is a better way to go.
Now, let’s see some code in action.
package org.kodejava.spring.core;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
public class InitDisposeService implements InitializingBean, DisposableBean {
/**
* Do some processes.
*/
public void doSomething() {
System.out.println("InitDisposeService.doSomething");
}
/**
* Initialize bean after property set.
*/
@Override
public void afterPropertiesSet() {
System.out.println("InitDisposeService.afterPropertiesSet");
}
/**
* Clean-up bean when the context is closed.
*/
@Override
public void destroy() {
System.out.println("InitDisposeService.destroy");
}
}
As usual, we define our Spring configuration (init-dispose.xml) to register our bean. In this case we will create a bean with id called service and will be using the InitDisposeService class.
<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
<bean id="service" class="org.kodejava.spring.core.InitDisposeService" />
</beans>
Below is a small Java program that we can use to run our application. This will load the Spring configuration, get the bean from the container and execute the bean. We’ll see that the afterPropertiesSet method is called. And when the context is closed the destroy method is also executed.
package org.kodejava.spring.core;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class InitDisposeDemo {
public static void main(String[] args) {
ConfigurableApplicationContext context =
new ClassPathXmlApplicationContext("init-dispose.xml");
InitDisposeService service =
(InitDisposeService) context.getBean("service");
service.doSomething();
context.close();
}
}
Here are the output printed on the screen:
InitDisposeService.afterPropertiesSet
InitDisposeService.doSomething
InitDisposeService.destroy
Maven Dependencies
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.3.23</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.3.23</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>5.3.23</version>
</dependency>
</dependencies>
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