Learn Java for Web Development

CHAPTER 5: Building Java Web Applications with Spring Web MVC 211

Application Context

Spring comes with several implementations of the ApplicationContext interface out of the box.
The three most commonly used are the following:

   ClassPathXmlApplicationContext: Loads a context definition from an XML file

located in the class path

   FileSystemXmlApplicationContext: Loads a context definition from an XML file

in the file system

   XmlWebApplicationContext: Loads context definitions from an XML file

contained within a web application

In stand-alone applications, it is common to create an instance of ClassPathXmlApplicationContext
or FileSystemXmlApplicationContext.

Following Figure 5-1, you have to instantiate the Spring IoC container (ApplicationContext) for it to
create bean instances by reading their configurations (configuration metadata). Then, you can get
the bean instances from the IoC container to use.

Listing 5-8 illustrates the instantiation of the ClassPathXmlApplicationContext, an implementation
of ApplicationContext. The ClassPathXmlApplicationContext implementation builds an application
context by loading an XML configuration file from the class path.

Listing 5-8. Instantiation of ClassPathXmlApplicationContext

ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

Listing 5-9 illustrates the instantiation of the FileSystemXmlApplicationContext.

Listing 5-9. Instantiation of the FileSystemXmlApplicationContext

ApplicationContextcontext=new FileSystemXmlApplicationContext("c:/beans.xml");

Note The FileSystemXmlApplicationContext looks for beans.xml in a specific location within the

file system, whereas ClassPathXmlApplicationContext looks for beans.xml anywhere in the class

path (including JAR files).

In the section that follows, you will learn how to use the application context when you create your
first Spring-based stand-alone application.