Скачать или смотреть Resolving the no main manifest attribute Error in Spring Boot Applications on Heroku

Learn how to fix the `no main manifest attribute` error during Spring Boot application deployment on Heroku. Follow our step-by-step guide for a successful deployment.
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Resolving the no main manifest attribute Error in Spring Boot Applications on Heroku

Deploying a Spring Boot application on Heroku can sometimes throw unexpected errors. One of the most frustrating errors developers might encounter is the no main manifest attribute error during deployment. If you've recently faced this issue, you're not alone! In this post, we’ll explore the causes of this error and, most importantly, how to fix it.

Understanding the Problem

After successfully building your Spring Boot application locally and even running it without issues, you might find that pushing it to Heroku results in the error message:

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This message indicates that Heroku cannot find the main class specified in the JAR file's manifest. This can be due to incorrect configurations in your pom.xml or how Heroku builds your project.

Why This Happens

When deploying to Heroku, it typically executes the mvn clean install command to build your application. During this process, if the JAR file’s manifest does not contain the necessary main class information, Heroku will fail to start the application, resulting in an application error.

Steps to Resolve the Error

Step 1: Modify Your pom.xml

The first thing you should check is the configuration in your pom.xml. The critical aspect that often leads to the error is the <pluginManagement> section. Heroku might not read this section correctly, leading to missing settings when building the JAR file.

Remove <pluginManagement> from your pom.xml:

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Instead, directly add the spring-boot-maven-plugin under the <plugins> section without using <pluginManagement>:

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Step 2: Rebuild Your Application

Once you've made the changes, you need to rebuild your application:

Open your terminal or command prompt.

Navigate to your project directory.

Run:

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This command builds the project and packages the resulting JAR file into the target directory.

Step 3: Push to Heroku

Now, with your changes committed, push your application to Heroku:

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Additional Notes

If you had added the plugins under <pluginManagement> to avoid errors in your IDE (like Eclipse), it may have been unnecessary. Removing this section allows Heroku to correctly identify and utilize your plugin configurations.

Always ensure that your MANIFEST.MF file in your JAR has the Main-Class and other necessary attributes defined for Spring Boot applications.

Conclusion

By removing the <pluginManagement> tag from your pom.xml file and rebuilding your application, you can resolve the no main manifest attribute error while deploying your Spring Boot application on Heroku. Following these steps should ensure a smooth deployment process.

If you continue to experience issues, double-check your MANIFEST.MF file and confirm that the necessary attributes are correctly specified. Happy coding, and enjoy deploying your Spring Boot applications!