@PostConstruct and @PreDestroy Annotation in Spring
March 27, 2022
@PostConstruct and @PreDestroy annotation in Spring. The @PostConstruct and @PreDestroy are JSR-250 annotations. They belong to javax.annotation package.
@PostConstruct
The
@PostConstruct annotation marks a method as initialization method of a bean which runs after dependency injection is completed. The @PostConstruct method can be used to validate properties of bean or initializing any task just after dependency injection is completed. In a bean class, there must be only one method annotated with @PostConstruct. This method cannot be static. The @PostConstruct annotation is equivalent to init-method attribute of XML <bean> element.
@PreDestroy
The
@PreDestroy annotation marks a method that is executed just before the bean is destroyed by Spring container. The method annotated with @PreDestroy can be used to release the resources or preform any destruction task before the container destroys the bean. There must be only one method in our bean annotated with @PreDestroy. This method cannot be static. The @PreDestroy annotation is equivalent to destroy-method attribute of XML <bean> element.
Example
Book.java
package com.concretepage;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
public class Book {
private String bookName;
public Book(String bookName) {
this.bookName = bookName;
}
@PostConstruct
public void springPostConstruct() {
System.out.println("---Do initialization task---");
if(bookName != null) {
System.out.println("bookName property initialized with the value:"+ bookName);
}
}
public String getBookName() {
return bookName;
}
@PreDestroy
public void springPreDestroy() {
System.out.println("---Release resources or perform destruction task---");
}
}
package com.concretepage;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class AppConfig {
@Bean
public Book book(){
return new Book("Ramayana");
}
}
SpringDemo.java
package com.concretepage;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class SpringDemo {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
ctx.register(AppConfig.class);
ctx.refresh();
Book book = ctx.getBean(Book.class);
System.out.println("Book name:" + book.getBookName());
ctx.close();
}
}
---Do initialization task--- bookName property initialized with the value:Ramayana Book name:Ramayana ---Release resources or perform destruction task---
