Resolving No suitable driver found for jdbc:postgresql Error When Running a Single JAR File in Scala

This guide explains how to fix the `No suitable driver found for jdbc:postgresql` error when executing a single JAR file in Scala using sbt-assembly. Learn the necessary steps to ensure PostgreSQL dependencies are included correctly.
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Resolving No suitable driver found for jdbc:postgresql Error When Running a Single JAR File in Scala

When working with Scala projects that connect to a PostgreSQL database, many developers face a frustrating issue: encountering a No suitable driver found for jdbc:postgresql error when attempting to run their application packaged as a single JAR file. This dilemma generally occurs when using the sbt-assembly plugin, which is intended to bundle all required dependencies into one JAR.

In this post, we will unravel the reasons behind this error and provide detailed steps to resolve it so you can run your JAR file without additional configuration hassle.

Understanding the Issue

Here’s a brief breakdown of the problem:

You have established a Scala project using sbt and are successfully connecting to a PostgreSQL database when running it from IntelliJ IDE.

After packaging your application with sbt-assembly into a single JAR, you are unable to run the JAR due to the No suitable driver found for jdbc:postgresql:// exception.

On investigating, you found that the PostgreSQL JDBC driver was missing from your JAR file.

This scenario indicates that the PostgreSQL driver dependency is not being included during the JAR assembly process.

To investigate the issue, let’s review a sample sbt configuration:

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

Key Points to Consider

Dependency Inclusion: Ensure the PostgreSQL JDBC driver is listed in libraryDependencies. It appears correct in your configuration, which is a good sign.

Driver Class Loading: When using the PostgreSQL driver, ensure you explicitly load it every time you create a database connection:

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

Clean Up Unused Dependencies: If you have other database-related dependencies (like Oracle or MySQL), consider removing them if they are not required. This simplifies your build and may help to prevent conflicts.

Running the JAR File Successfully

To ensure you can run the JAR without providing external dependencies manually, follow these steps:

Test Execution: Run the newly packaged JAR:

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

Conclusion

By following the steps and recommendations outlined in this post, you should be able to resolve the No suitable driver found for jdbc:postgresql error and run your Scala application effectively from a single JAR file. Always ensure the correct JDBC driver is included and properly loaded in your application code.

If you have any more questions or need further assistance, feel free to reach out!