Apache Tomcat Web Server Explained in Simple Terms

Explore the world of Apache Tomcat, a powerful open-source web server for Java applications. This guide covers its workings, features, comparisons with other web servers, installation, configuration, and more.

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Dimitri Nek
Dimitri Nek
Web Hosting Geek

Apache Tomcat Web Server Logo

Apache Tomcat stands as a beacon of reliability and versatility in the vast landscape of application servers. This open-source software has carved out a niche for itself, powering countless web applications worldwide with its robust capabilities and seamless integration with Java technologies. But what exactly is Apache Tomcat, and why has it become such a staple in the world of web hosting?

In this comprehensive guide, we will delve into the heart of Apache Tomcat, exploring how it works, and the unique features that set it apart from the competitors. We will also examine how it interacts with different environments, how it compares with other application servers, and how you can install and configure it to suit your specific needs.

Whether you’re a seasoned web developer, a budding tech enthusiast, or a business owner looking to understand more about your web hosting options, this guide is designed to equip you with a deeper understanding of Apache Tomcat.

Let’s get started.

Key Takeaways:

  • Apache Tomcat is an open-source web server that specializes in running Java applications. It’s known for its robustness, flexibility, and active community support, making it a popular choice for many organizations worldwide.
  • Apache Tomcat works by implementing several Java EE specifications such as Java Servlet, JavaServer Pages (JSP), and Java Expression Language (EL). It also features a modular architecture with components like Catalina, Coyote, and Jasper playing crucial roles.
  • When compared to other web servers like Nginx, Apache, IIS, and Lightspeed, Apache Tomcat stands out for its seamless compatibility with Java applications. However, each web server has its strengths and ideal use cases.
  • Apache Tomcat can be deployed in various environments, including Linux, Windows, and the cloud. Each environment has its unique considerations, and Apache Tomcat provides the flexibility to accommodate these differences, making it a versatile choice for diverse deployment scenarios.
  • Apache Tomcat can interact with databases through JDBC DataSources. This feature allows Java applications running on Apache Tomcat to easily connect to a database, execute SQL queries, and process the results.

What is Apache Tomcat

Apache Tomcat, often referred to simply as Tomcat, is an open-source web server and servlet container developed by the Apache Software Foundation. It implements several Java EE specifications including Java Servlet, JavaServer Pages (JSP), Java EL, and WebSocket, providing a pure Java HTTP web server environment for Java code to run in.

Brief History and Development of Apache Tomcat Web Server

The development of Apache Tomcat began in 1998 as a reference implementation for the Java Servlet and JavaServer Pages (JSP) technologies, which were being developed by Sun Microsystems.

The project was initially part of the Jakarta Project, a now-retired open-source community of developers working on various Java-related projects under the auspices of the Apache Software Foundation.

Over the years, Tomcat has evolved and matured, with numerous versions being released, each bringing new features, improvements, and bug fixes.

Case Studies

Apache Tomcat is used by a wide range of organizations, from small startups to large corporations, due to its robustness, flexibility, and open-source nature. Here are a few examples of successful implementations of Apache Tomcat:

  1. Walmart: The retail giant uses Apache Tomcat for its e-commerce website, handling millions of transactions daily. Tomcat’s scalability and robustness make it an ideal choice for such a high-traffic environment.
  2. The Weather Channel: The Weather Channel uses Apache Tomcat to serve its digital platforms, providing weather updates to millions of users worldwide. The company appreciates Tomcat’s stability and the active community support.
  3. LinkedIn: The professional networking site uses Apache Tomcat as part of its server stack. Tomcat’s ability to handle large numbers of simultaneous connections makes it a good fit for LinkedIn’s high-traffic environment.
  4. Alfresco: This leading open-source content management system uses Apache Tomcat as its default server. Alfresco appreciates Tomcat’s seamless integration with Java, its main programming language.
  5. Liferay: This open-source portal uses Apache Tomcat due to its strong support for Java, robust performance, and scalability.

These examples illustrate the versatility of Apache Tomcat and its ability to handle a wide range of use cases. Whether you’re running a small application or a high-traffic website, Apache Tomcat is a reliable, robust choice for your web server needs.

Importance and Role of Apache Tomcat in Web Hosting

Apache Tomcat plays a crucial role in web hosting, particularly when it comes to running Java applications. As a servlet container, Tomcat provides the necessary environment for Java code to execute in the context of a web application. This makes it an essential tool for developers working with Java-based web technologies.

Moreover, Tomcat’s open-source nature means it benefits from the collective efforts of a vast community of developers. This not only leads to continuous improvements and updates but also ensures that users have access to a wealth of shared knowledge and resources.

In the broader context of web hosting, Apache Tomcat is often used in conjunction with the Apache HTTP Server, where Tomcat serves dynamic content via Java Servlets and JSPs, while the HTTP Server handles static content.

This combination leverages the strengths of both servers, providing a robust, flexible, and high-performance solution for serving web applications.

How Apache Tomcat Works

At its core, Apache Tomcat is a servlet container. It provides the environment within which Java Servlets and JavaServer Pages (JSP) can operate.

When a request comes into Tomcat, it is processed by the servlet container. The container creates a new thread for each request, and the servlet or JSP page is loaded and executed within that thread. Once the servlet or JSP page has completed its processing, a response is generated and sent back to the client.

Apache Tomcat and Java

Apache Tomcat’s relationship with Java is integral to its operation. Tomcat is designed to run Java code, specifically Java Servlets, JavaServer Pages (JSP), and Java Expression Language (EL).

Java Servlets are server-side Java programs that handle requests from clients, typically web browsers, and return a response. JavaServer Pages (JSP) are similar to servlets but allow for a more natural approach to creating static content, with the ability to embed Java code within HTML pages. Java Expression Language (EL) is used within JSP to simplify access to Java objects.

These technologies are central to the operation of Apache Tomcat, allowing it to serve dynamic web content efficiently and effectively.

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Understanding Apache Tomcat Architecture

Apache Tomcat’s architecture is modular and flexible, consisting of several key components. The primary components are Catalina, Coyote, and Jasper.

Catalina is Tomcat’s servlet container. It implements the Servlet and JSP specifications and manages the lifecycle of servlets and JSP pages.

Coyote is the connector component that handles incoming requests and forwards them to the appropriate container for processing. It also handles the responses from the containers.

Jasper is the JSP engine that converts JSP pages into servlets for execution by Catalina.

These components work together to process requests and deliver responses, providing a robust and efficient web server environment.

Features and Capabilities of Apache Tomcat

Apache Tomcat boasts a wide range of features and capabilities. At its core, it provides a robust, efficient, and flexible environment for running Java Servlets and JSP pages. It supports all major versions of the Servlet and JSP specifications, ensuring compatibility with a wide range of Java web applications.

Tomcat also supports a variety of additional features, such as SSL/TLS for secure connections, HTTP/2 for improved performance, and WebSocket for real-time communication. It also provides advanced features like clustering and load balancing for handling high traffic loads and ensuring high availability.

Apache Tomcat in Different Environments

Apache Tomcat is platform-independent, meaning it can run on any operating system that supports a compatible Java Runtime Environment (JRE). This includes Linux, Windows, and various Unix-based systems.

Running Apache Tomcat in cloud environments is also a popular choice. Cloud providers like AWS, Google Cloud, and Azure offer services that can host Tomcat applications, providing scalability, reliability, and ease of deployment. However, running Tomcat in the cloud can come with its own set of challenges, such as dealing with distributed environments and managing resources effectively.

Apache Tomcat vs Other Web Servers

When it comes to web server software, there are several popular options available, each with its own strengths, weaknesses, and ideal use cases. Let’s compare Apache Tomcat with some of these options: Nginx, Apache HTTP Server, Microsoft IIS, and LiteSpeed.

Apache Tomcat Nginx Apache HTTP Server Microsoft IIS LiteSpeed
Java Support Yes No No No No
Performance High Very High High Moderate Very High
Flexibility High High Very High High High
Operating System Compatibility Cross-platform Cross-platform Cross-platform Windows Cross-platform
Ideal Use Cases Java applications Static content, Load balancing, Reverse proxy General purpose Windows environments Performance-critical environments

Apache Tomcat vs Nginx: Nginx is a high-performance HTTP server and reverse proxy server. Unlike Tomcat, which is a servlet container for running Java applications, Nginx is primarily used for serving static content and as a load balancer or reverse proxy for dynamic content. Nginx is known for its high performance, especially under high loads, and its ability to handle many concurrent connections. However, it does not natively support Java applications, which is where Tomcat shines.

Apache Tomcat vs Apache HTTP Server: Apache HTTP Server is a general-purpose web server designed to serve both static and dynamic content. While it can serve dynamic content through modules like mod_php for PHP applications, it does not natively support Java applications like Tomcat does. Apache HTTP Server is known for its flexibility and wide range of features, but it may not perform as well as Tomcat or Nginx under high loads.

Apache Tomcat vs Microsoft IIS: Microsoft IIS is a web server designed for Windows environments. It supports a range of programming languages through its ISAPI interface, including .NET languages, PHP, and Python. However, it does not natively support Java applications. IIS is tightly integrated with the Windows operating system, which can be an advantage in Windows environments, but it is not available for other operating systems.

Apache Tomcat vs LiteSpeed: LiteSpeed is a commercial web server designed for performance and scalability. It supports a wide range of programming languages, including PHP and Ruby, through its LSAPI interface. However, like the other servers mentioned, it does not natively support Java applications. LiteSpeed is known for its high performance, especially when serving PHP applications, and its compatibility with Apache HTTP Server’s mod_rewrite rules.

In summary, while each of these web servers has its strengths and ideal use cases, Apache Tomcat stands out for its ability to natively run Java applications. This makes it the go-to choice for serving Java Servlets and JSP pages. However, it’s not uncommon to see Tomcat used in conjunction with another web server like Nginx or Apache HTTP Server, where Tomcat serves the dynamic Java content and the other server handles static content and other tasks.

Installation and Configuration of Apache Tomcat

– Installing Apache Tomcat

Installing Apache Tomcat involves a few key steps:

  1. Download Apache Tomcat: Visit the official Apache Tomcat website and download the latest stable version of Tomcat. The download will be a compressed (.zip or .tar.gz) file.
  2. Extract the Files: Once the download is complete, extract the files to your desired location. This will be your Tomcat installation directory.
  3. Set Environment Variables: For Tomcat to work properly, you need to set the JAVA_HOME environment variable to point to your Java Development Kit (JDK) installation directory.
  4. Run Tomcat: Navigate to the bin directory inside your Tomcat installation directory and run the startup.sh (for Linux/Unix) or startup.bat (for Windows) script. This will start the Tomcat server.
  5. Verify Installation: Open a web browser and navigate to http://localhost:8080. If Tomcat has been installed correctly, you should see the Tomcat welcome page.

– Configuring Apache Tomcat

Once Tomcat is installed, you can configure it to suit your needs. The main configuration file for Tomcat is the server.xml file, located in the conf directory of your Tomcat installation.

Here are some basic configuration settings you might want to adjust:

  • HTTP Connector Port: By default, Tomcat listens for HTTP requests on port 8080. You can change this by locating the <Connector> element with the attribute protocol="HTTP/1.1" and changing the port attribute to your desired port number.
  • Enable HTTPS: To enable HTTPS, you need to create a <Connector> element for the HTTPS protocol. This requires a keystore file containing the server’s SSL certificate and private key.
  • Memory Allocation: You can adjust the amount of memory allocated to Tomcat by setting the Xms and Xmx options in the CATALINA_OPTS environment variable.
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Remember, configuring Tomcat optimally depends on your specific use case and environment. For more detailed configuration options, refer to the official Tomcat documentation or check out our tutorials in our How-To Section.

Security, Performance, and Optimization of Apache Tomcat

– Security Features of Apache Tomcat

Apache Tomcat comes with a number of built-in security features, but it’s also important to follow best practices to ensure your server is secure. Here are some practical steps you can take:

  1. Update Regularly: Always keep your Tomcat server updated to the latest version. This ensures that you have the latest security patches and improvements.
  2. Use Strong Passwords: The Tomcat Manager and Host Manager applications, if used, should be protected with strong, unique passwords.
  3. Limit Access: Restrict access to sensitive areas of your server. This includes the Tomcat Manager, Host Manager, and any administrative interfaces.
  4. Use HTTPS: If you’re transmitting sensitive data, make sure to enable HTTPS to encrypt the data in transit.
  5. Disable Unnecessary Features: If you’re not using certain features or services, it’s a good idea to disable them to reduce potential attack vectors.

– Performance and Optimization

Optimizing Apache Tomcat for performance involves a number of strategies:

  1. Tune JVM Parameters: The Java Virtual Machine (JVM) parameters can have a significant impact on Tomcat’s performance. This includes settings for memory allocation, garbage collection, and JIT compilation.
  2. Optimize Thread Pool Settings: The thread pool settings control how Tomcat handles incoming connections. Optimizing these settings can help ensure that Tomcat can handle high loads efficiently.
  3. Enable GZIP Compression: Enabling GZIP compression can help reduce the size of the data sent to clients, improving response times.
  4. Use a Content Delivery Network: If you’re serving static content, using a CDN can help reduce load on your Tomcat server and improve response times for users around the world.
  5. Monitor Performance: Regularly monitor your server’s performance to identify any potential bottlenecks or issues. Tools like JMX and VisualVM can be very helpful for this.

Remember, optimizing Tomcat is a continuous process that involves monitoring, tweaking, and testing. Always test any changes in a staging environment before applying them to your production server.

Apache Tomcat and Databases

Apache Tomcat interacts with databases primarily through the Java Database Connectivity (JDBC) API. This API provides a standard interface for Java applications to interact with a wide range of databases. It allows developers to write database code that is independent of the underlying database system.

JDBC DataSources in Apache Tomcat

In the context of Apache Tomcat, a DataSource is an object that provides database connectivity through a pool of database connections. This is also known as a connection pool. Connection pools can significantly improve performance for applications that require frequent access to a database.

Tomcat’s JDBC DataSource is configured in the context of a web application and is typically defined in the context configuration file (context.xml) of the application. The DataSource configuration includes details such as the JDBC driver class, the database URL, username, password, and other settings related to the connection pool such as the initial size, maximum number of active connections, and so on.

Once the DataSource is configured, it can be retrieved in a Java Servlet or JSP page via JNDI (Java Naming and Directory Interface) lookup and used to establish a connection to the database.

Here’s an example of how a DataSource might be configured in the context.xml file:

<Resource name="jdbc/MyDB"

And here’s how it might be used in a servlet:

Context initContext = new InitialContext();
Context envContext = (Context)initContext.lookup("java:/comp/env");
DataSource ds = (DataSource)envContext.lookup("jdbc/MyDB");
Connection conn = ds.getConnection();

By using a DataSource and connection pooling, Apache Tomcat can efficiently manage database connections, improving performance and scalability for database-intensive applications.

Troubleshooting Apache Tomcat

When working with Apache Tomcat, you may encounter a variety of issues. Here are some common problems and their solutions:

  • Tomcat is not starting: This could be due to a variety of reasons, such as port conflicts, incorrect environment variables, or issues with the Tomcat configuration files. Check the Tomcat logs (located in the logs directory of your Tomcat installation) for any error messages that could indicate what’s going wrong.
  • HTTP 404 errors: If you’re seeing 404 errors when trying to access your web application, it could mean that the application is not properly deployed or that the URL is incorrect. Check that your application is correctly placed in the webapps directory and that the URL correctly points to your application.
  • Out of memory errors: If Tomcat is running out of memory, you may need to increase the amount of memory allocated to Tomcat. This can be done by adjusting the Xms and Xmx options in the CATALINA_OPTS environment variable.
  • Database connectivity issues: If your application is having trouble connecting to a database, check that your DataSource configuration is correct and that the database is running and accessible.

Resources for Getting Help

If you’re having trouble resolving an issue, there are several resources available to help:

  • Official Documentation: The official Apache Tomcat documentation is a comprehensive resource that covers all aspects of installing, configuring, and running Tomcat.
  • Mailing Lists: The Apache Tomcat project maintains several mailing lists where you can ask questions and get help from the Tomcat community.
  • Forums and Q&A Sites: Websites like Stack Overflow have a large number of questions and answers related to Tomcat. You can search for your issue to see if others have encountered the same problem, or ask a new question if your issue is not covered.
  • Issue Tracker: If you believe you’ve found a bug in Tomcat, you can report it on the Apache Tomcat issue tracker.

Remember, when asking for help, it’s important to provide as much relevant information as possible, including error messages, log output, and details about your environment and configuration. This will make it easier for others to understand your issue and provide assistance.

Apache Tomcat and the Open-Source Community

Apache Tomcat is a significant player in the open-source community. Its development and maintenance are driven by a community of developers and users who contribute their time and expertise to improve and enhance the software. This collaborative effort has made Apache Tomcat a robust and reliable web server that is used by organizations worldwide.

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Role of Apache Tomcat in the Open-Source Community

Apache Tomcat’s role in the open-source community is multifaceted:

  1. Promoting Open-Source Culture: By being an open-source project, Apache Tomcat promotes a culture of transparency, collaboration, and shared knowledge. It allows anyone to view its source code, understand its workings, and contribute to its development.
  2. Providing a Reliable Web Server Solution: Apache Tomcat provides a reliable, open-source web server solution for Java web applications. This has made it a popular choice among developers and organizations, thereby strengthening the open-source ecosystem.
  3. Fostering Innovation: Apache Tomcat’s open-source nature allows developers to experiment, innovate, and enhance its features. This fosters innovation and leads to the development of new features and capabilities.

How to Contribute to the Apache Tomcat Project

Contributing to the Apache Tomcat project is a great way to give back to the community, improve your skills, and make a tangible impact on a widely used software. Here’s how you can contribute:

  • Understanding the Code: Start by understanding the Apache Tomcat codebase. You can access the source code from the Apache Tomcat website.
  • Joining the Mailing Lists: Apache Tomcat has user and developer mailing lists. Join these lists to stay updated on the latest discussions, issues, and developments.
  • Reporting Issues: If you come across any bugs or issues while using Apache Tomcat, report them. This helps the developers to fix the issues and improve the software.
  • Submitting Patches: If you can fix an issue or enhance a feature, you can submit a patch. Make sure to follow the Apache Tomcat patch submission guidelines.
  • Documentation: Good documentation is crucial for any software project. You can contribute by improving the existing documentation or creating new documentation where needed.

Remember, every contribution, no matter how small, is valuable and helps in making Apache Tomcat better.

What’s Next?

The future of Apache Tomcat is promising and continues to evolve with the changing landscape of web server technology. Here are some key developments to look forward to:

  1. Continued Support for Newer Java Versions: Apache Tomcat has a history of keeping up with the latest Java versions. As of now, Apache Tomcat 11.0.x supports Java 17 and later versions. This trend is expected to continue, ensuring that Tomcat remains compatible with future Java releases.
  2. Enhancements in Specifications: Apache Tomcat’s versions are aligned with the specifications of Jakarta EE (formerly Java EE). The latest version, Apache Tomcat 11.0.x, implements Servlet 6.1, JSP 4.0, EL 6.0, WebSocket TBD, and Authentication (JASPIC) TBD specifications. As these specifications evolve, so will Apache Tomcat.
  3. Improved Performance and Stability: Apache Tomcat is consistently working on performance optimizations and stability improvements. Future versions of Tomcat are expected to offer even better performance, scalability, and reliability.
  4. Increased Cloud Compatibility: With the growing trend of cloud computing, Apache Tomcat is likely to enhance its features and compatibility with cloud environments. This will make it easier for organizations to deploy and manage their Tomcat servers in the cloud.
  5. Community Contributions: Being an open-source project, Apache Tomcat benefits from the contributions of its community. This collective effort will continue to drive the development and improvement of Tomcat in the future.

Remember, the future is always subject to change, and these trends are based on the current trajectory of Apache Tomcat’s development. It’s always a good idea to keep an eye on the official Apache Tomcat website for the latest news and updates.


Apache Tomcat is a powerful, versatile, and reliable web server that has proven its worth in the world of web hosting. Its compatibility with Java applications, robust features, and active community make it a preferred choice for many organizations. From small businesses to large corporations, Apache Tomcat is trusted to deliver high performance, security, and scalability.

Throughout this guide, we’ve explored the inner workings of Apache Tomcat, its key features, and how it compares to other web servers. We’ve also delved into its installation and configuration, its interaction with databases, and how to troubleshoot common issues. Moreover, we’ve highlighted the role of Apache Tomcat in the open-source community and how you can contribute to its development.

As we look towards the future, Apache Tomcat continues to evolve, keeping pace with the latest trends in web server technology. Whether it’s supporting newer Java versions, enhancing its specifications, improving performance and stability, or increasing cloud compatibility, Apache Tomcat is committed to meeting the needs of its users.

In conclusion, whether you’re a developer, a system administrator, or someone interested in web server technology, understanding Apache Tomcat is highly beneficial. It equips you with the knowledge to effectively host and manage Java web applications, contributing to your skills in the ever-evolving field of web technology.

We hope this guide has been informative and helpful. If you have any questions or thoughts, feel free to leave a comment. We’d love to hear from you!


  1. What is Apache Tomcat and why is it important?

    Apache Tomcat is an open-source web server that specializes in running Java applications. It’s important because of its robustness, flexibility, and active community support, making it a popular choice for many organizations worldwide.

  2. How does Apache Tomcat compare to other web servers?

    Apache Tomcat stands out from other web servers like Nginx, Apache, IIS, and Lightspeed for its seamless compatibility with Java applications. However, each web server has its strengths and ideal use cases.

  3. How do I install and configure Apache Tomcat?

    Installing Apache Tomcat involves downloading the software and setting environment variables. Configuration involves adjusting settings in the Tomcat configuration files. For optimal performance, it’s important to customize the configuration according to your needs.

  4. What role does Apache Tomcat play in the open-source community?

    Apache Tomcat plays a significant role in the open-source community, promoting a culture of transparency, collaboration, and shared knowledge. Users can contribute to the project by understanding the code, joining mailing lists, reporting issues, submitting patches, and improving documentation.

  5. What is the future of Apache Tomcat?

    The future of Apache Tomcat is promising. It continues to evolve with the latest trends in web server technology, including supporting newer Java versions, enhancing its specifications, improving performance and stability, and increasing cloud compatibility.


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