Spring @PostConstruct and @PreDestroy - Example
Annotations @PostConstruct and @PreDestroy, standardized by JSR-250, are generally considered the best practice for obtaining lifecycle callbacks in a modern Spring application.
- @PostConstruct annotation defines a method that will run only once, just after the initialization of bean.
- @PreDestroy annotation defines a method that will run only once, just before Spring removes the bean from the application context.
Complete Example
We are creating a simple maven project. You could clone the code from our GitHub repo.
Final Project Directory
Complete pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.knf.dev.demo</groupId>
<artifactId>postconstruct-predestroy-example</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>17</maven.compiler.source>
<maven.compiler.target>17</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>6.1.0</version>
</dependency>
<dependency>
<groupId>jakarta.annotation</groupId>
<artifactId>jakarta.annotation-api</artifactId>
<version>2.1.1</version>
</dependency>
</dependencies>
</project>
We have to add jakarta.annotation dependency to use these annotations.
Create Component class
package com.knf.dev.demo;
import jakarta.annotation.PostConstruct;
import jakarta.annotation.PreDestroy;
import org.springframework.stereotype.Component;
@Component
public class MyComponent {
@PostConstruct
public void postConstruct() throws Exception {
System.out.println("After bean initialization");
}
@PreDestroy
public void preDestroy() {
System.out.println("Perform destructive task or release resources.");
}
public void printMessage() {
System.out.println("Hello");
}
}
Create Config
package com.knf.dev.demo;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan
public class Config {
}
Spring provides a mechanism to identify application component explicitly through the @ComponentScan annotation. We are not passing arguments to @ComponentScan, letting Spring to scan the current package and all of its sub-packages.
Create main class - Application.java
package com.knf.dev.demo;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
public class Application {
public static void main(String[] args) {
AbstractApplicationContext context =
new AnnotationConfigApplicationContext(Config.class);
MyComponent myComponent = context.getBean(MyComponent.class);
myComponent.printMessage();
context.close();
}
}
The AbstractApplicationContext.close() method will close the application context, and destroying all cached singleton beans.
Console Output:
After bean initialization
Hello
Perform destructive task or release resources.
After bean initialization
Hello
Perform destructive task or release resources.
Source code
Are you preparing for Spring certification or preparing for Spring interview? Then below examples are interesting for you!
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