Posted in: ApplicationContext In Spring,Bean Lifecycle in Spring,Bean scopes in Spring,Spring Framework,Spring IoC
While the beans package provides basic functionality for managing and manipulating beans, often in a programmatic way, the context package adds ApplicationContext, which enhances BeanFactory functionality in a more framework-oriented style.
A bean factory is fine for simple applications, but to take advantage of the full power of the Spring Framework, you’ll probably want to load your application beans using Spring’s more advanced container, the application context.
Many users will use ApplicationContext in a completely declarative fashion, not even having to create it manually, but instead relying on support classes such as ContextLoader to automatically start an ApplicationContext as part of the normal startup process of a J2EE web-app. Of course, it is still possible to programmatically create an ApplicationContext.
The basis for the context package is the ApplicationContext interface, located in the org.springframework.context package. Deriving from the BeanFactory interface, it provides all the functionality of BeanFactory.
You could also implement your own ApplicationContext and add support for loading from other resources (such as a database). While many Contexts are available for loading beans, you’ll only need a few, which are listed below. The others are internal classes that are used by the framework itself.
1 ) ClassPathXmlApplicationContext: Loads context files from the classpath (that is, WEB-INF/classes or WEB-INF/lib for JARs) in a web application. Initializes using a
2 ) FileSystemXmlApplicationContext: Loads context files from the file system, which is nice for testing. Initializes using a
3. XmlWebApplicationContext: Loads context files internally by the ContextLoaderListener, but can be used outside of it. For instance, if you are running a container that doesn’t load Listeners in the order specified in web.xml, you may have to use this in another Listener. Below is the code to use this Loader.
Once you’ve obtained a reference to a context, you can get references to beans using
A bean factory is fine for simple applications, but to take advantage of the full power of the Spring Framework, you’ll probably want to load your application beans using Spring’s more advanced container, the application context.
Many users will use ApplicationContext in a completely declarative fashion, not even having to create it manually, but instead relying on support classes such as ContextLoader to automatically start an ApplicationContext as part of the normal startup process of a J2EE web-app. Of course, it is still possible to programmatically create an ApplicationContext.
The basis for the context package is the ApplicationContext interface, located in the org.springframework.context package. Deriving from the BeanFactory interface, it provides all the functionality of BeanFactory.
You could also implement your own ApplicationContext and add support for loading from other resources (such as a database). While many Contexts are available for loading beans, you’ll only need a few, which are listed below. The others are internal classes that are used by the framework itself.
1 ) ClassPathXmlApplicationContext: Loads context files from the classpath (that is, WEB-INF/classes or WEB-INF/lib for JARs) in a web application. Initializes using a
new ClassPathXmlApplicationContext(path)
where path is the path to the file. 2 ) FileSystemXmlApplicationContext: Loads context files from the file system, which is nice for testing. Initializes using a
new FileSystemXmlApplicationContext (path)
where path is a relative or absolute path to the file. The path argument can also be a String array of paths.3. XmlWebApplicationContext: Loads context files internally by the ContextLoaderListener, but can be used outside of it. For instance, if you are running a container that doesn’t load Listeners in the order specified in web.xml, you may have to use this in another Listener. Below is the code to use this Loader.
XmlWebApplicationContext context =
new XmlWebApplicationContext();
context.setServletContext(ctx);
context.refresh();
Once you’ve obtained a reference to a context, you can get references to beans using
ctx.getBean(“beanId”)
You will need to cast it to a specific type, but that’s the easy part. Of the above contexts, ClassPathXmlApplicationContext is the most flexible. It doesn’t care where the files are, as long as they’re in the classpath. This allows you to move files around and simply change the classpath.
Related Topics :
- Spring Framework Tutorial-Part1
- Spring IoC (Dependency injection ) Tutorial - Part 2
- Bean Creation in spring - Tutorial Part - 3
- Spring Basic Bean Creation Example
- Spring IoC Constructor Injection Example - Tutorial
- Spring IoC setter Injection Example - Tutorial
- Purpose of the ApplicationContext in Spring