Apache Tomcat Configuration Files

Apache Tomcat uses a set of core configuration files to manage server behavior, application deployment, user access, and resource integration. Located in the conf/ directory, these files define key components such as ports, connectors, servlet mappings, security roles, and logging levels.

Understanding these files like server.xml, context.xml, web.xml, and tomcat-users.xml is essential for customizing Tomcat in development or production environments. Here, we covers their purpose, location, and configuration with practical examples.

Tomcat Directory Structure

After installation (e.g., in /opt/tomcat), the typical directory layout looks like:

/opt/tomcat
├── bin/            # Scripts to start/stop Tomcat
├── conf/           # All main configuration files
├── webapps/        # Deployed apps (WAR files or folders)
├── logs/           # Log output (catalina.out, etc.)
├── lib/            # Java libraries used by Tomcat
├── temp/, work/, etc.

Key Configuration Files and Their Purpose

1. server.xml – Main Tomcat Configuration

• Path: /opt/tomcat/conf/server.xml
• Purpose: This is the core file that defines how Tomcat runs: its ports, services, connectors, and virtual hosts.

Key Elements:

• <Connector>: Defines how Tomcat accepts HTTP/HTTPS requests.
• <Host>: Lets you host multiple applications (or domains) on the same server.
• <Engine> and <Service>: Control overall server behavior and how requests are processed.

Example: Change Default HTTP Port

<Connector port="8081" protocol="HTTP/1.1"
                      connectionTimeout="20000"
                      redirectPort="8443" />

• This changes the HTTP port from 8080 to 8081.
• Access the app at http://localhost:8081 instead of 8080.

Note: Restart Tomcat for changes to take effect.

2. context.xml – Global or Application Context Settings

Tomcat uses this file to define environment-specific settings like JNDI resources (databases, caches, etc.).

Paths:

• Global Context: /opt/tomcat/conf/context.xml
• Per-Application: yourapp/META-INF/context.xml

Used For:

• Setting up JNDI resources (e.g., database connections)
• Defining environment variables
• Enabling hot deployment during development

Example:

Add a MySQL resource:

<Context>
  <Resource name="jdbc/mydb" auth="Container"
            type="javax.sql.DataSource"
            driverClassName="com.mysql.cj.jdbc.Driver"
            url="jdbc:mysql://localhost:3306/mydb"
            username="root" password="password" />
</Context>

3. web.xml – Web Application Deployment Descriptor

This file defines how a web application behaves, such as URL mappings, servlets, filters, and default pages.

Paths:

• Global: /opt/tomcat/conf/web.xml (applies to all apps)
• App-Specific: WEB-INF/web.xml

Used For:

• Declaring servlets and their classes
• Mapping URLs to servlets
• Defining filters, listeners, error pages, and welcome files

Example: HelloServlet Mapping

<servlet>
  <servlet-name>HelloServlet</servlet-name>
  <servlet-class>com.example.HelloServlet</servlet-class>
</servlet>

<servlet-mapping>
  <servlet-name>HelloServlet</servlet-name>
  <url-pattern>/hello</url-pattern>
</servlet-mapping>

Now, accessing http://localhost:8080/yourapp/hello invokes the HelloServlet.

Best practice: Define this in WEB-INF/web.xml to keep it app-specific.

4. tomcat-users.xml – Tomcat User Access Control

• Path: /opt/tomcat/conf/tomcat-users.xml
• Purpose: Manage users and roles for accessing Tomcat’s Manager and Host Manager GUIs.

Example: Add Admin User

<tomcat-users>
  <role rolename="manager-gui"/>
  <role rolename="admin-gui"/>
  <user username="admin" password="admin123" roles="manager-gui,admin-gui"/>
</tomcat-users>

Access the admin interface at:

• http://localhost:8080/manager/html
• http://localhost:8080/host-manager/html

Security Tip: Never use weak credentials in production. Always update the default passwords!

5. logging.properties – Logging Configuration

• Path: /opt/tomcat/conf/logging.properties
• Purpose: Controls how Tomcat writes logs to /opt/tomcat/logs/.

Used For:

• Setting log levels (INFO, DEBUG, WARNING, etc.)
• Changing output format or destinations
• Debugging specific Tomcat components

Example: Increase Logging for Catalina (Core Component)

org.apache.catalina.level = FINE

You will now see more detailed logs in /opt/tomcat/logs/catalina.out, which helps during debugging.