I am studying Spring framework, in web.xml I added following which is a bootstrap listener. Can anyone give me a proper idea of what is a bootstrap listener?
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
You can see the doc here: ContextLoadListener
Bootstrap listener to start up and shut down Spring’s root WebApplicationContext. Simply delegates to
ContextLoaderas well as toContextCleanupListener.This listener should be registered after
Log4jConfigListenerin web.xml, if the latter is used.As of Spring 3.1,
ContextLoaderListenersupports injecting the root web application context via theContextLoaderListener(WebApplicationContext)constructor, allowing for programmatic configuration in Servlet 3.0+ environments. See WebApplicationInitializer for usage examples…
It’s an event listener as defined in the servlet standard. Basically, it’s a way to execute code when the servlet container has started the web app.
Spring’s ContextLoaderListener uses this mechanism to create the WebApplicationContext, which involves reading and parsing all bean configuration XML files, as well as (depending on the configuration) instantiating the singleton beans.