BeanPostProcessors in Spring

This is 14 of 16 parts of tutorial series

Tutorial Content: Spring tutorial for beginners

BeanPostProcessors interface provides methods that you can implement to have your own instantiation logic.Also you can write your own logic after spring IOC finishes instantiating, configuring, and initializing a bean by plugging in one or more BeanPostProcessor implementations.

You can configure multiple BeanPostProcessors and also can decide the order in which they will run relative to each other by setting order property but foe that BeanPostProcessors  have to implement ordered interface.

Extension of BeanPostProcessor is BeanFactoryPostProcessor interface which allows direct modification of bean definitions before a bean is instantiated

An ApplicationContext will automatically register and process a bean that implements either of these interfaces, but a BeanFactory would have to have a BeanPostProcessor or BeanFactoryPostProcessor registered with it programatically.

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.InitCapitalPostProcessor.java:

This is simple pojo class implementing BeanPostProcessor interface.
Create InitCapitalPostProcessor.java under package org.arpit.javapostsforlearning.Copy following content into InitCapitalPostProcessor.java.

 Here we are writing very simple logic but you can write quite complex logic  in above functions.You can note that you have object of bean class here so you can change it in whatever way you want and can return same or different object.

3.BeanPostProcessorExampleMain.java

This class contains main function.Create BeanPostProcessorExampleMain.java under package org.arpit.javapostsforlearning.Copy following content into BeanPostProcessorExampleMain.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.ApplicationContext.xml

5.Run it

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

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