You can use @Bean to make an existing third-party class available to your Spring framework application context.
@Bean
public ViewResolver viewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setPrefix("/WEB-INF/view/");
viewResolver.setSuffix(".jsp");
return viewResolver;
}
By using the @Bean annotation, you can wrap a third-party class (it may not have @Component and it may not use Spring), as a Spring bean. And then once it is wrapped using @Bean, it is as a singleton object and available in your Spring framework application context. You can now easily share/reuse this bean in your app using dependency injection and @Autowired.
So think of the @Bean annotation is a wrapper/adapter for third-party classes. You want to make the third-party classes available to your Spring framework application context.
By using @Bean in the code above, I'm explicitly declare a single bean because inside of the method, I'm explicitly creating the object using the new keyword. I'm also manually calling setter methods of the given class. So I can change the value of the prefix field. So this manual work is referred to as explicit creation. If I use the @Component for the same class, the bean registered in the Spring container will have default value for the prefix field.
On the other hand, when we annotate a class with @Component, no need for us to manually use the new keyword. It is handled automatically by Spring.