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Monday, 17 March 2014

Spring Destruction callbacks

In this tutorial we are going to see about Spring Life cycle Destruction callbacks with example program.
Implementing the org.springframework.beans.factory.DisposableBean interface allows a bean to get a callback when the container containing it is destroyed. The DisposableBean interface specifies a single method:
void destroy() throws Exception;

It is recommended that you do not use the DisposableBean callback interface because it unnecessarily couples the code to Spring. Alternatively, use the @PreDestroy annotation or specify a generic method that is supported by bean definitions. With XML-based configuration metadata, you use the destroy-method attribute on the <bean/>. For example, the following definition:

<bean id="cleanupBean" class="com.javatutorialscorner.spring.SpringDestructionCallback" destroy-method="cleanup"/>

public class SpringDestructionCallback{

public void cleanup() {
// do some destruction work (like releasing pooled connections)
}
}

...is exactly the same as...

<bean id="destroyBean" class="com.javatutorialscorner.spring.SpringDestructionCallback1"/>

public class SpringDestructionCallback1 implements DisposableBean {

public void destroy() {
// do some destruction work (like releasing pooled connections)
}
}

... but does not couple the code to Spring. We will see both types with example.

Step by step procedure to create Spring Program using Eclipse given below.

Follow the Simple steps.

1. Select File –> New –> Java Project from your Eclipse IDE.

2.Create project called SpringDisposableBean.

3. Add the following jars into your build path.

commons-logging-1.1.3.jar
spring-beans-3.2.6.RELEASE.jar
spring-context-3.2.6.RELEASE.jar
spring-context-support-3.2.6.RELEASE.jar
spring-core-3.2.6.RELEASE.jar
spring-expression-3.2.6.RELEASE.jar

4. Now create package com.javatutorialscorner.spring under SpringDisposableBean Project

5. Next create SpringDestructionCallback class under com.javatutorialscorner.spring package . This class using cleanup() method to destroy bean.

SpringDestructionCallback.java

package com.javatutorialscorner.spring;

public class SpringDestructionCallback {
private String sayHello;

public void getSayHello() {
System.out.println("Java Tutorials Corner " + sayHello);
}

public void setSayHello(String sayHello) {
this.sayHello = sayHello;
}

public void cleanup() throws Exception {
// TODO Auto-generated method stub
System.out
.println("Inside SpringDestructionCallback - cleanup() method - bean will destroy now");
}
}

5. Next create SpringDestructionCallback1 class under com.javatutorialscorner.spring package . This class implements DisposableBean and using default destroy() method to destroy bean.

SpringDestructionCallback1 .java

package com.javatutorialscorner.spring;

import org.springframework.beans.factory.DisposableBean;

public class SpringDestructionCallback1 implements DisposableBean {

private String sayHello;

public void getSayHello() {
System.out.println("Java Tutorials Corner " + sayHello);
}

public void setSayHello(String sayHello) {
this.sayHello = sayHello;
}

@Override
public void destroy() throws Exception {
// TODO Auto-generated method stub
System.out.println("Inside SpringDestructionCallback1 - destroy() method - bean will destroy now");

}
}

7. Now Create RunApp class which contains Bean configuration path to load configuration from Bean.xml file

RunApp.java

package com.javatutorialscorner.spring;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class RunApp {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

AbstractApplicationContext context = new ClassPathXmlApplicationContext(
"Beans.xml");
SpringDestructionCallback destructionBean = (SpringDestructionCallback) context
.getBean("cleanupBean");
destructionBean.getSayHello();

SpringDestructionCallback1 destructionBean1 = (SpringDestructionCallback1) context
.getBean("destroyBean");
destructionBean1.getSayHello();

context.registerShutdownHook();
}

}

In above program

First step I created Application context using ClassPathXmlApplicationContext  which load configuration from bean file  which located in class path of apllication, It take care of creating and initializing all the objects (Beans) declared in bean.xml

Next getBean() method used to get particular bean from created context. This method used bean name as parameter and returns generic object. We can caste to actual object.

Once Object Created you can access any method from that class.

The registerShutdownHook() method declared in AbstractApplicationContext class, which ensure the graceful shutdown and class relevant destroy method.

7. Create Bean.xml at where your class files created (ClassPathXmlApplicationContext tries to load bean file from class path).

Bean.xml

<?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="cleanupBean" class="com.javatutorialscorner.spring.SpringDestructionCallback" destroy-method="cleanup">
<property name="sayHello" value="cleanupBean"></property>
</bean>
<bean id="destroyBean" class="com.javatutorialscorner.spring.SpringDestructionCallback1" >
<property name="sayHello" value="destroyBean"></property>
</bean>
</beans>

Bean.xml is default name given to bean configuration file. You can choose any name for your bean.xml but you can use file name in main application to create context and your file available in your class path must be same.

Bean.xml is used to assign unique ID to different beans and controls the creation object with different values, using above file you can pass any value to   variable sayHello without changing the class file.

Now you can run the program see the following output in console.

Java Tutorials Corner cleanupBean
Java Tutorials Corner destroyBean
Inside SpringDestructionCallback1 - destroy() method - bean will destroy now
Inside SpringDestructionCallback - cleanup() method - bean will destroy now
Annamalai Thangaraj

Annamalai is working as Technical Lead in Leading Telecom company with 5+ years experience in Identity and Access Management , Telecom and Networks, BigData, Java, Spring, Struts, Hibernate, AngularJS, and Enterprise Web Application Development.

Website: Java Tutorials Corner

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Item Reviewed: Spring Destruction callbacks Rating: 5 Reviewed By: Annamalai Thangaraj