Application contexts provide a means for resolving text messages?

One of the main advatage stated for Application Context is below :-

Application contexts provide a means for resolving text messages

Could somebody explain with brief example what does that mean?

Second is there any overhead of开发者_开发知识库 using Application contexts over BeanFactory as i have seen most of the application using BeanFactory?

Here is the declaration of ApplicationContext:

public interface ApplicationContext extends
    ListableBeanFactory,
    HierarchicalBeanFactory,
    MessageSource,
    ApplicationEventPublisher,
    ResourcePatternResolver {

One of the interfaces it extends is MessageSource:

Strategy interface for resolving messages, with support for the parameterization and internationalization of such messages.

From MessageSource Javadoc. This means you can use application context as a message source for your application with I18N support. Spring has a small framework for resolving messages, pattern replacement, etc.

With regards to your seconds question: you should always use the smallest possible interface you need. When you are injecting BeanFactory, it is probably an ApplicationContext, but there is no need to couple your class with such a huge abstraction. Just pick what you are going to use.