Spring lifetime callbacks

This is 13 of 16 parts of tutorial series

Tutorial Content:

The Spring Framework provides several callback interfaces to change the behavior of your bean in the container; they include InitializingBean and DisposableBean.

The life cycle of a Spring bean is easy to understand. When a bean is instantiated, it may be required to perform some initialization to get it into a usable state. Similarly, when the bean is no longer required and is removed from the container, some cleanup may be required.

Initialization callbacks:

Implementing the org.springframework.beans.factory.InitializingBean interface allows a bean to perform initialization work after all necessary properties on the bean have been set by the container. The InitializingBean interface specifies exactly one method:

Generally, the use of the InitializingBean interface can be avoided and is actually discouraged since it unnecessarily couples the code to Spring.You have to use  afterPropertiesSet(),you can not change name of method.There is alternative for this i.e. XML-based configuration metadata.This is done using the 'init-method' attribute of tag.It provides flexibility of changing method name.

…is exactly the same as…

… but does not couple the code to Spring.

Destruction callbacks:

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:
 Generally, the use of the DisposableBean interface can be avoided and is actually discouraged since it unnecessarily couples the code to Spring.You have to use  destroy(),you can not change name of method.There is alternative for this i.e. XML-based configuration metadata.This is done using the 'destroy-method' attribute of tag.It provides flexibility of changing method name.
…is exactly the same as…
… but does not couple the code to Spring.

Spring lifetime callbacks Example:

For configuring spring in your eclipse ide please refer  hello world example

1.Country.java

This is simple pojo class having some attributes so here country has name.
Create Country.java under package org.arpit.javapostsforlearning.Copy following content into Country.java.

2.ApplicationContext.xml

3.LifetimeCallbacksMain.java

This class contains main function.Create LifetimeCallbacksMain.java under package org.arpit.javapostsforlearning.Copy following content into LifetimeCallbacksMain.java
Here you need to register a shutdown hook registerShutdownHook() method that is declared on the AbstractApplicationContext class. This will ensures a graceful shutdown and calls the relevant destroy methods.

4.Run it

When you will run above application,you will get following as output.

Default Initialization and destroy method:

If you have too many beans having initialization and or destroy methods with the same name, you don’t need to declare init-method and destroy-method on each individual bean. Instead framework provides the flexibility to configure such situation using default-init-method and default-destroy-method attributes on the element as follows:

That’s all about Spring lifetime callbacks.


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