{"id":5550,"date":"2012-05-12T14:07:53","date_gmt":"2012-05-12T08:37:53","guid":{"rendered":"https:\/\/tothenewco.pro\/blog\/?p=5550"},"modified":"2015-07-09T16:01:21","modified_gmt":"2015-07-09T10:31:21","slug":"overriding-properties-in-a-spring-bean-with-beanfactorypostprocessor","status":"publish","type":"post","link":"https:\/\/tothenewco.pro\/blog\/overriding-properties-in-a-spring-bean-with-beanfactorypostprocessor\/","title":{"rendered":"Overriding properties in a Spring Bean with BeanFactoryPostProcessor"},"content":{"rendered":"

I was going through the source code of one of the Grails Plugins where I found the use of Spring’s BeanDefinitionRegistryPostProcessor<\/a> to override some configurations that are available in DataSource.groovy. That involved a complete over riding of a PropertyValue<\/a> definition.<\/p>\n

 <\/p>\n

It set me thinking about whether there is a way to override bean properties like String, Integer etc in a simpler way after the bean has initialized. In comes BeanFactoryPostProcessor<\/a>, which provides a wonderful hook to do just that.<\/p>\n

 <\/p>\n

I created a small grails project and added a class CustomBean which looked like this :<\/p>\n

[java]<\/p>\n

class CustomBean {
\n String customVariable
\n}
\n[\/java]<\/p>\n

I registered a customBean<\/em> on resources.groovy using<\/p>\n

[java]
\nbeans = {
\n customBean(CustomBean) {
\n String value = "Test Data From resources.groovy"
\n println "Setting value ${value}"
\n customVariable = value
\n }<\/p>\n

customBeanPostProcessor(CustomBeanPostprocessor)
\n}
\n[\/java]<\/p>\n

This sets the initial value of customVariable<\/em> as “Test Data From resources.groovy”.<\/p>\n

If you are wondering what the customBeanPostprocessor is, that is just what I am going to explain next.
\nThe bean implements the BeanFactoryPostProcessor interface and overrides the methods which provides us with hooks to modify the properties of the bean.<\/p>\n

 <\/p>\n

The class definition is:<\/p>\n

[java]
\nimport groovy.util.logging.Log4j
\nimport org.springframework.beans.factory.config.BeanPostProcessor<\/p>\n

@Log4j
\nclass CustomBeanPostprocessor implements BeanPostProcessor{<\/p>\n

@Override
\n Object postProcessBeforeInitialization(Object bean, String beanName) {
\n return bean
\n }<\/p>\n

@Override
\n Object postProcessAfterInitialization(Object bean, String beanName) {
\n if(beanName == ‘customBean’) {
\n log.debug("Setting custom value inside post processor")
\n bean.customVariable = "Set from Post Processor"
\n }
\n return bean
\n }
\n}
\n[\/java]<\/p>\n

What amazed me is the elegance with which the developers of the framework<\/a> has provided entry points into its internals without forcing the users to shave the yak.<\/p>\n","protected":false},"excerpt":{"rendered":"

I was going through the source code of one of the Grails Plugins where I found the use of Spring’s BeanDefinitionRegistryPostProcessor to override some configurations that are available in DataSource.groovy. That involved a complete over riding of a PropertyValue definition.   It set me thinking about whether there is a way to override bean properties […]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":9,"footnotes":""},"categories":[7],"tags":[819,4840,4841,820],"class_list":["post-5550","post","type-post","status-publish","format-standard","hentry","category-grails","tag-bean-post-processing","tag-grails","tag-spring","tag-spring-internals"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t