dyatesdude dyatesdude - 2 months ago 8
Java Question

Heroku, Java, Procfile, Could not find or load main class

I'm using heroku with maven to run a server. My goal is to have heroku run the java class server.class as a web dyno.

How would I write a procfile to execute the java program server.class as web?



My current Procfile

web: java -cp $JAVA_OPTS target/classes/v1/a1/server


My error.(From heroku logs)

Picked up JAVA_TOOL_OPTIONS: -Xmx350m -Xss512k -Dfile.encoding=UTF-8
Error: Could not find or load main class target.classes.v1.a1.server
State changed from starting to crashed





Possibly useful information

The procfile

web: java -cp $JAVA_OPTS target/classes/v1/a1/*


Returns

Error: Could not find or load main class target.classes.v1.a1.myOtherClass


My original Procfile(Also didn't work)

web: java -cp target/classes/:target/dependency/* server



  • My file structure is a bit different than the example given in the heroku docs so I modified the procfile a bit.
  • My dependencies are not inside /target/dependencies.
  • My classes are inside target/classes/v1/a1/.
  • server.java has a main method and valid constructor method.
  • All my dependencies seem to be in order.
  • Maven does builds my .java files into .class files in the target directory.
  • I'm on unix so quotes and semicolons probably won't work.

Answer

I think your Procfile should contain:

web: java -cp target/classes/:target/dependency/* v1.a1.server

This assumes the following:

  • Your server class is in the file target/v1/a1/server.class
  • The Java code for your server class includes package v1.a1;
  • Your class name and file name are lowercase.

A few problems I noticed in your earlier attempts included:

  • You are passing $JAVA_OPTS to the -cp options (incorrect)
  • You are using / instead of . in the fully qualified class name (incorrect)
  • You are including the target dir in the fully qualified class name (incorrect)

The files in the target/classes/ and target/dependency/ directory belong on the classpath (i.e. passed to -cp) while the last argument to the java command should be the fully qualified class name (in the form package.Class).

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