Error during deploy Vaadin application at heroku - status code 503 'State changed from starting-CodePudding

I try to run my vaadin application. After build run successfully, an error appears on the screen. Any ideas ?

2022-08-02T05:06:05.575314 00:00 heroku[web.1]: Starting process with command `java $JAVA_OPTS -jar target/qrcodegen-1.0-SNAPSHOT.jar  $JAR_OPTS`
2022-08-02T05:06:06.505888 00:00 app[web.1]: Setting JAVA_TOOL_OPTIONS defaults based on dyno size. Custom settings will override them.
2022-08-02T05:06:06.509226 00:00 app[web.1]: Picked up JAVA_TOOL_OPTIONS: -Xmx300m -Xss512k -XX:CICompilerCount=2 -Dfile.encoding=UTF-8 
2022-08-02T05:06:06.606402 00:00 app[web.1]: no main manifest attribute, in target/qrcodegen-1.0-SNAPSHOT.jar
2022-08-02T05:06:06.740068 00:00 heroku[web.1]: Process exited with status 1
2022-08-02T05:06:06.795271 00:00 heroku[web.1]: State changed from starting to crashed
2022-08-02T05:07:19.953424 00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=kodikos.herokuapp.com request_id=7479eaae-5d81-4552-b9f5-0c0f2bc15f6d fwd="37.225.85.157" dyno= connect= service= status=503 bytes= protocol=https
2022-08-02T05:07:20.504159 00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=kodikos.herokuapp.com request_id=b2f6f781-86c2-4ff6-81ca-260c466d8fba fwd="37.225.85.157" dyno= connect= service= status=503 bytes= protocol=https
2022-08-02T05:13:27.592886 00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=kodikos.herokuapp.com request_id=499ea233-160a-4335-98f7-3907ac937b8e fwd="37.225.85.157" dyno= connect= service= status=503 bytes= protocol=https
2022-08-02T05:13:28.318168 00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=kodikos.herokuapp.com request_id=5f17545f-bc9a-4e46-8671-ace31a023016 fwd="37.225.85.157" dyno= connect= service= status=503 bytes= protocol=https
```
github repo: https://github.com/rafalsionkowski/qr-code-gen

CodePudding user response：

The error is

no main manifest attribute, in target/qrcodegen-1.0-SNAPSHOT.jar

Without any main attribute Java does not know which class to execute.

Normally the spring-maven-plugin will rewrite the built jar and add needed metadata such as a main attribute. You seem to be missing that plugin