What's the Difference Between `applicationContext.xml` and `spring-servlet.xml` in Spring Web Applications?

applicationContext.xml vs spring-servlet.xml in Spring Framework

In Spring Framework, dependency injection and component configuration are commonly managed through XML files, namely applicationContext.xml and spring-servlet.xml. These XML files play distinct roles and are interconnected in the application architecture.

Relationship between applicationContext.xml and spring-servlet.xml

Spring supports defining multiple application contexts organized in a parent-child hierarchy. applicationContext.xml defines the root webapp context, which serves as the overarching context for the application. On the other hand, spring-servlet.xml defines the application context for a specific DispatcherServlet, allowing for dedicated contexts for each Spring servlet within the webapp.

Properties File Availability

Property files declared in applicationContext.xml are accessible to all child contexts, including those defined in spring-servlet.xml. This means that DispatcherServlet has access to the properties defined in applicationContext.xml.

Need for *-servlet.xml

-servlet.xml files are necessary because they provide specialized configuration for Spring servlets. These servlets typically handle specific aspects of the application, such as HTTP requests. Without -servlet.xml files, the servlets would not have access to the necessary bean definitions and configurations. In most cases, applicationContext.xml alone is not sufficient to handle the specific requirements of Spring servlets.

Conventions and Hierarchy

applicationContext.xml typically defines shared beans that are common to all servlets in the webapp. If there is only one servlet, applicationContext.xml can be omitted. spring-servlet.xml is used to configure beans specific to the DispatcherServlet, including controllers and other components tied to HTTP requests. Beans defined in spring-servlet.xml can reference beans in applicationContext.xml, but the reverse is not possible, ensuring a clear hierarchy and isolation between contexts.

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