When you use WAR files to deploy applications on a Tomcat server, the structure of directories in a WAR file must conform to a specific standard. The directory of a web project contains various resources, such as application code, configuration files, and static files.

Structure of a project directory

To compile and package a project with ease, we recommend that you use the following structure to organize files in the project. 

tomcat-webapp
└── src
    └── main
        ├── java                - A directory that contains source code
        │   └── com
        │       └── demoapp
        │           └── Hello.java
        ├── resources             - A directory that contains resource configuration files
        │   └── application.properties
        └── webapp
            ├── 404.jsp             - A JSP page that shows an HTTP 404 error message
            ├── WEB-INF             - A secure directory that isolates internal resources from clients
            │   ├── classes           - A directory that contains compiled classes
            │   ├── lib             - A directory that contains JAR libraries
            │ │ └── mysql-connector-java-8.0.8-dmr.jar
            │   ├── views           - A directory that contains display templates
            │   │   └── index.mustache      
            │   └── web.xml           - A deployment descriptor file
            ├── index.jsp           - A JSP file
            └── static              - A directory that contains static resource files
                ├── css             - A directory that contains CSS resource files
                │   └── demoapp.css
                ├── fonts           - A directory that contains font resource files
                ├── images            - A directory that contains image resource files
                │   └── demoapp.png
                └── js              - A directory that contains JavaScript files
                    └── bootstrap.min.js

The src/main/java directory contains source Java class files. Each file forms part of an application. These source files are stored in the src/main/webapp/WEB-INF/classes directory and will be compiled into .class files that are accessible by an application. These .class files are stored in the webapp/WEB-INF/classes directory. Then, the webapp root directory that includes all files and subdirectories are packaged and deployed to a web server.

Structure of the webapp root directory

The webapp root directory contains resources, such as HTML files, JSP files, and static resources. These resources and the WEB-INF subdirectory will be packaged and deployed to a web server.

In the webapp directory, all resources are accessible by clients excluding resources that are included in the WEB-INF subdirectory. For example, you can use a client to access 404.jsp and index.jsp. The static subdirectory contains CSS files, image files, JavaScript files, and other resources. These resources are also accessible by clients. 

webapp
├── 404.jsp
├── WEB-INF
├── index.jsp
└── static
    ├── css
    │   └── demoapp.css
    ├── fonts
    ├── images
    │   └── demoapp.png
    └── js
        └── bootstrap.min.js

Structure of the WEB-INF subdirectory

The WEB-INF subdirectory that resides in the webapp root directory is a secure directory of a Java web application. Resources stored in the subdirectory are accessible by backend servers and are not accessible by clients. The WEB-INF subdirectory contains the following resources:
  • The classes subdirectory that contains .class files. The .class files are compiled from the source application code that you develop.
  • The lib subdirectory that contains various JAR files associated with the web application, for example, JAR files that contains database drivers.
  • Web page template files, such as mustache files.
  • A deployment descriptor file named web.xml.
WEB-INF
├── classes         - A directory that contains compiled classes
├── lib             - A directory that contains JAR libraries
├── views           - A directory that contains Web page template files
└── web.xml         - A deployment descriptor file