Spring Bean Life Cycle Methods – InitializingBean, DisposableBean, @PostConstruct, @PreDestroy and *Aware interfaces

Spring Beans are the most important part of any Spring application. Spring ApplicationContext is responsible to initialize the Spring Beans defined in spring bean configuration file.

Spring Context is also responsible for injection dependencies in the bean, either through setter/constructor methods or by spring autowiring.

Sometimes we want to initialize resources in the bean classes, for example creating database connections or validating third party services at the time of initialization before any client request. Spring framework provide different ways through which we can provide post-initialization and pre-destroy methods in a spring bean.

1. By implementing InitializingBean and DisposableBean interfaces – Both these interfaces declare a single method where we can initialize/close resources in the bean. For post-initialization, we can implement InitializingBean interface and provide implementation of afterPropertiesSet() method. For pre-destroy, we can implement DisposableBean interface and provide implementation of destroy() method. These methods are the callback methods and similar to servlet listener implementations.

   This approach is simple to use but it’s not recommended because it will create tight coupling with the Spring framework in our bean implementations.

2. Providing init-method and destroy-method attribute values for the bean in the spring bean configuration file. This is the recommended approach because of no direct dependency to spring framework and we can create our own methods.

Note that both post-init and pre-destroy methods should have no arguments but they can throw Exceptions. We would also require to get the bean instance from the spring application context for these methods invocation.

@PostConstruct and @PreDestroy Annotations

Spring framework also support @PostConstruct and @PreDestroy annotations for defining post-init and pre-destroy methods. These annotations are part of javax.annotation package. However for these annotations to work, we need to configure our spring application to look for annotations. We can do this either by defining bean of type org.springframework.context.annotation.CommonAnnotationBeanPostProcessor or by context:annotation-config element in spring bean configuration file.

Let’s write a simple Spring application to showcase the use of above configurations. Create a Spring Maven project in Spring Tool Suite, final project will look like below image.

Spring Maven Dependencies

We don’t need to include any extra dependencies for configuring spring bean life cycle methods, our pom.xml file is like any other standard spring maven project.

<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>org.springframework.samples</groupId>
  <artifactId>SpringBeanLifeCycle</artifactId>
  <version>0.0.1-SNAPSHOT</version>
   
  <properties>
 
        <!-- Generic properties -->
        <java.version>1.7</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 
        <!-- Spring -->
        <spring-framework.version>4.0.2.RELEASE</spring-framework.version>
 
        <!-- Logging -->
        <logback.version>1.0.13</logback.version>
        <slf4j.version>1.7.5</slf4j.version>
 
    </properties>
     
    <dependencies>
        <!-- Spring and Transactions -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
 
        <!-- Logging with SLF4J & LogBack -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>${logback.version}</version>
            <scope>runtime</scope>
        </dependency>
 
    </dependencies>  
</project>

pom.xml