Скачать или смотреть Resolving the JNDI Resource Name Lookup Error in Tomcat 9 Startup

Discover how to fix `NamingContext.lookup` errors in Tomcat 9 when launching applications with JNDI resource configurations.
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This video is based on the question https://stackoverflow.com/q/68761943/ asked by the user 'Paul Stoner' ( https://stackoverflow.com/u/4215616/ ) and on the answer https://stackoverflow.com/a/71310011/ provided by the user 'Mahe' ( https://stackoverflow.com/u/2611134/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting the JNDI Resource Name Lookup Error in Tomcat 9 Startup

When working with containerized applications that connect to a MariaDB instance, encountering errors during application startup can be a significant hurdle. A common issue developers face is the NamingContext.lookup error, which can be particularly frustrating when everything seems configured correctly. This guide aims to dissect the problem and guide you through effective solutions to tackle this error in Tomcat 9.

The Problem: NamingContext.lookup Error on Startup

Imagine you have two applications—Application A and Application B—configured to use the same JNDI resources in Tomcat, yet only Application B throws a NamingContext.lookup error upon startup. Despite verifying that both applications have identical configurations in server.xml and context.xml, the error persists. Specifically, the error message indicates a NullPointerException, giving no clear direction on where to look for the issue.

Log Excerpt Illustrating the Error

A glance at the logs reveals a stack trace indicating that the Tomcat server encounters a NullPointerException when attempting to resolve a JNDI resource reference for Application B, while Application A runs without any issues. This discrepancy in behavior under seemingly identical configurations is where the mystery lies.

Analyzing the Configuration

Resource Configuration Overview

Both applications define a JNDI resource in their respective server.xml files, which looks like this for both Application A and Application B:

[[See Video to Reveal this Text or Code Snippet]]

Context XML Configuration

The context.xml files for both applications also appear similar, with Application A using multiple ResourceLink entries while Application B has only the jdbc/menudb resource link defined.

The Solution: Update the Resource Configuration

The primary issue leading to the NullPointerException in Application B is related to the factory that creates the data source. For Tomcat 9 specifically, you need to ensure that the resource is configured with the appropriate factory. Here’s a resolution to implement for your server.xml file

Correct JNDI Resource Definition

You should modify the JNDI resource definition in your server.xml for Application B as follows:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Explained

Factory Parameter: The addition of factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" explicitly defines the factory that Tomcat should use to create the data source, which is integral for correct initialization.

Type Specification: Specifying type="org.apache.tomcat.jdbc.pool.DataSource" ensures that Tomcat understands the type of resource being referenced.

Conclusion

Debugging JNDI resource issues in Tomcat can be challenging, especially when identical configurations behave differently across applications. By ensuring the correct factory and data source type are defined, you can eliminate many of the common pitfalls that lead to lookup errors. Implementing these changes not only resolves the NamingContext.lookup issue for Application B but enhances your understanding of how Tomcat manages JNDI resources.

If you find yourself stuck or experiencing further errors, don't hesitate to delve deeper into your configurations or reach out to the community for support. Your journey toward a smoothly running containerized application starts with the right configuration!