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🔔 Subscribe on YouTubeWhat Are @PostConstruct and @PreDestroy Annotations?
In the Spring Framework, managing the lifecycle of a bean is essential for initializing resources and ensuring clean shutdowns. The @PostConstruct and @PreDestroy annotations are part of the standard Java annotations (JSR-250) supported seamlessly by Spring.
They offer a clean, readable, annotation-driven approach to execute custom startup and teardown logic without coupling your classes to Spring-specific interfaces.
Understanding @PostConstruct
The @PostConstruct annotation is placed on a method that needs to run immediately after dependency injection is complete and the bean has been fully initialized.
- Initialization Logic: Ideal for loading configuration files, opening database connections, or pre-caching required data.
- Safety: Guarantees that all autowired properties and dependencies are ready to use.
Understanding @PreDestroy
The @PreDestroy annotation marks a callback method that executes just before the Spring container destroys the bean instance during application shutdown.
- Resource Cleanup: Used to close open streams, release file locks, or shut down active worker threads safely.
- Graceful Shutdown: Prevents memory leaks and connection hanging when your application stops.
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| Spring Bean Life Cycle - Spring @PostConstruct and @PreDestroy Annotations | Spring Tutorial |
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| Spring Bean Life Cycle - Spring @PostConstruct and @PreDestroy Annotations | Spring Tutorial |
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| Spring Bean Life Cycle - Spring @PostConstruct and @PreDestroy Annotations | Spring Tutorial |
<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>
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 javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
public class Employee
{
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;
}
@PostConstruct
public void init() throws Exception
{
System.out.println("inside Init method after properties are set. ");
}
@PreDestroy
public void cleanUp() throws Exception
{
System.out.println("Inside cleanUp(), Performed clean up tasks.");
}
@Override
public String toString()
{
return "Employee [id=" + id + ", name=" + name + "]";
}
}
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
public class Employee
{
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;
}
@PostConstruct
public void init() throws Exception
{
System.out.println("inside Init method after properties are set. ");
}
@PreDestroy
public void cleanUp() throws Exception
{
System.out.println("Inside cleanUp(), 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>
<context:annotation-config />
</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>
<context:annotation-config />
</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();
}
}
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 07, 2018 10:27:26 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Tue Aug 07 10:27:26 IST 2018]; root of context hierarchy
Aug 07, 2018 10:27:26 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [applicationContext.xml]
inside Init method after properties are set.
---------------------------------------
Got employee object from the ApplicationContext(Spring Container)
Employee [id=100, name=Peter]
Aug 07, 2018 10:27:26 AM org.springframework.context.support.AbstractApplicationContext doClose
INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Tue Aug 07 10:27:26 IST 2018]; root of context hierarchy
Inside cleanUp(), Performed clean up tasks.
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Tue Aug 07 10:27:26 IST 2018]; root of context hierarchy
Aug 07, 2018 10:27:26 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [applicationContext.xml]
inside Init method after properties are set.
---------------------------------------
Got employee object from the ApplicationContext(Spring Container)
Employee [id=100, name=Peter]
Aug 07, 2018 10:27:26 AM org.springframework.context.support.AbstractApplicationContext doClose
INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Tue Aug 07 10:27:26 IST 2018]; root of context hierarchy
Inside cleanUp(), Performed clean up tasks.
Click the below link to download the code:
https://sites.google.com/site/ramj2eev2/java_basics/SpringDemo_PostConstruct_PreDestroy.zip?attredirects=0&d=1
Github Link:
https://github.com/ramram43210/javaee/tree/master/Spring_2018/SpringDemo_PostConstruct_PreDestroy
Bitbucket Link:
https://bitbucket.org/ramram43210/spring/src/924507f5515578f632825f98c99b1cb6c7d7a7be/Spring_2018/SpringDemo_PostConstruct_PreDestroy/?at=master
See also:
