What is a WAR file and what is it used for in the process of developing and deploying applications?

A WAR (Web Application Archive) file is an archive that contains all components of a Java web application: compiled classes, libraries, configuration files, resources (HTML, CSS, JavaScript), and deployment descriptors (e.g., web.xml).

WAR files are used for packaging and deploying web applications on application servers (such as Apache Tomcat, JBoss). This simplifies the transfer and installation of the application, as all necessary files are collected in a single archive.

Example structure of a WAR file:

myapp.war
├── WEB-INF/
│   ├── classes/
│   ├── lib/
│   └── web.xml
├── index.html
└── resources/

Tools like Maven or Gradle are often used to create WAR files.