During web development, Apache Tomcat, a widely used open-source Java Servlet container, is often employed by developers to deploy Java Web applications. However, when starting Tomcat services, you may encounter an inability to open the localhost:8080 page, resulting in an Access Error: 404 — Not Found. This can cause considerable trouble for developers. This article aims to provide detailed steps to resolve this issue and offer optimization suggestions.

Problem Description

When you try to access http://localhost:8080 in a browser, you might encounter a 404 error, meaning the requested resource cannot be found. Typically, this indicates that the Tomcat server has started but hasn’t found the corresponding page or application.

Common Causes and Solutions

Port Conflict Issue

Cause Analysis: The most common cause is that the 8080 port is occupied by another application. Since 8080 is the default Tomcat port, it’s also often used by other development software, like some database management systems, other web servers, etc.

Solution:

  • Change the Tomcat startup port: Open the server.xml file in the conf folder of the Tomcat installation directory. Find the line <Connector port="8080" protocol="HTTP/1.1"> and change port=”8080″ to another unoccupied port, such as port=”9999″.
  • Restart Tomcat: After changing the port, save the server.xml file, go back to the Tomcat’s bin directory, first run shutdown.bat to close the Tomcat service, then double-click startup.bat to restart Tomcat. Now, you should be able to access the Tomcat homepage through the new port http://localhost:9999.

Configuration File Issue

Cause Analysis: If the port is not the issue, then it might be due to incorrect settings in Tomcat’s configuration files.

Solution:

  • Check Application Deployment: Confirm that your web application is correctly deployed in Tomcat’s webapps directory and that the application’s directory structure complies with the standards of Java Web applications.
  • Check the web.xml file: Ensure that your web application’s WEB-INF folder includes a correctly configured web.xml file. This file describes your application’s servlets and other components.

Other Possible Issues

  • Firewall Settings: Make sure that firewall settings are not blocking the port of the Tomcat service.
  • Service Not Started Properly: In some cases, the Tomcat service may not have started correctly. You can try to start Tomcat from the command line interface using catalina.bat run and check for any error messages output.