Скачать или смотреть Resolving 404 Errors in Java Servlets on Tomcat

Having trouble accessing your Java servlets on Tomcat, getting a `404 error`? Learn how to resolve the issue and ensure your deployment works seamlessly!
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Resolving 404 Errors in Java Servlets on Tomcat: A Step-by-Step Guide

Developing a web application that works seamlessly on your local environment is a common experience for developers. However, deploying the same application to an actual server can sometimes lead to unexpected errors, such as the dreaded 404 Not Found status. This post will explore a specific issue many developers face: Java servlets working on localhost but returning a 404 error once deployed on a hosting server.

Understanding the Problem

You’ve created a web application using Java Servlets, and everything works flawlessly on your local machine—until you deploy it to a hosting environment. Upon accessing your servlet via a specific URL, instead of getting the expected output, you encounter a 404 error. Why does this happen?

Here are the key symptoms:

Servlets returning a 404 error when accessed from the host URL (e.g., www.mysite/faq).

The same servlets function perfectly without error when accessed locally.

The correct class files are compiled and reside in the WEB-INF folder of your deployed application.

A manual mapping in the web.xml file has been attempted but is still resulting in errors.

Let’s troubleshoot this problem and walk through the solution step-by-step.

Identifying the Root Cause

After careful analysis of your setup, here are some common reasons for encountering a 404 error with Java Servlets after deployment:

Tomcat Version Mismatch: A different version of Tomcat on the hosting server compared to your local development environment can lead to compatibility issues.

JDK Version Issues: A discrepancy between the JDK version used in development and deployment can further exacerbate the situation.

Configuration Settings: Any discrepancies in the application configuration between local and hosted environments may also result in unwanted errors.

Steps to Resolve the Issue

Once the potential causes are identified, here’s how you can address the 404 error effectively:

1. Check the Tomcat Version

Ensure that the Tomcat version on your hosting server matches the version you used during development. As per your summary, you might have originally developed your project using Tomcat 7 but the server was configured to use Tomcat 10.

Solution: Contact your hosting provider and request that they adjust the server configuration to use the appropriate Tomcat version that is compatible with your application.

2. Align JDK Versions

Just as with Tomcat, aligning the JDK version is crucial. If your application was built using JDK 8 and the server runs JDK 10, the mismatch could lead to various issues, including the 404 error.

Solution: Ask the hosting provider to change the server configuration to use JDK 8 to align with your project requirements.

3. Verify Servlet Configuration

Even if you made attempts to define the servlet within web.xml, it’s good practice to double-check that the servlet name and URL pattern are set correctly:

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4. Test the Servlet Again

After making the necessary adjustments to your server configuration, try to access the servlet again. If everything aligns correctly:

Access www.mysite/faq and it should display the expected output without throwing a 404 error.

Conclusion

Encountering the 404 error when deploying Java servlets can be frustrating, especially when everything appears to work fine locally. However, addressing the version mismatches between Tomcat and JDK, along with ensuring proper servlet configuration, can aid in resolving the problem.

If you find yourself stuck, remember that reaching out to your hosting provider can often lead to the quickest resolution. With the appropriate adj