Java cannot find the main class <class>

What it means

The class <class> is not in the classpath: the jar was built without dependencies or the name is wrong.

The build passed, but the app did not start or did not answer the health check.

Typical causes

• The app does not listen on 0.0.0.0 and the port from the PORT variable
• An environment variable is missing, or the database or Redis is not connected
• The start command is wrong or the process exits right away

How to fix it on mevcore

Build an executable jar (Spring Boot plugin, shade or shadow) and start it with java -jar, or fix the class name in the start command in the settings.

1. 1 Open the app in the mevcore panel: the Problems card on the overview shows this error and the log line it was found in.
2. It is fixed on the “Settings” tab of the app.
3. 2 After the fix, deploy again. If it fails again, the log ends with [mevcore] lines naming the new error code.
4. 3 The "Ask AI" button next to the error prepares a request for ChatGPT or Claude: the error code, the end of the log without secrets and the app settings.

For an AI assistant

The same in English: paste it together with the log into the AI chat.

mevcore error code: runtime.java_main_class
phase: start / health check
diagnosis: Java cannot find the main class <class>
platform hint: The class <class> is not in the classpath: the jar was built without dependencies or the name is wrong. Build an executable jar (Spring Boot plugin, shade or shadow) and start it with java -jar, or fix the class name in the start command in the settings.
platform docs: https://mevcore.com/llms-full.txt

Related errors

• runtime.java_no_main_manifest The jar has no main class
• runtime.php_class_missing Class <class> not found
• runtime.java_version The code needs a newer Java
• runtime.laravel_target_class Laravel cannot find the class <class>