Why has it failed to load main-class manifest attribute from a JAR file?

Question

I have created a JAR file in this way jar cf jar-file input-files. Now, I\'m trying to run it. Running it does not work (jre command is not found):

Answer 1

I'm not sure I believe your symptoms:

• If the jre command isn't found, then running jre -cp app.jar should give the same error
• Just adding a JAR file to the classpath shouldn't give the error you're seeing

I'd expect you to see this error if you run:

java -jar app.jar

The Main-Class header needs to be in the manifest for the JAR file - this is metadata about things like other required libraries. See the Sun documentation for how to create an appropriate manifest. Basically you need to create a text file which includes a line like this:

Main-Class: MainClass

Then run

jar cfm app.jar manifest.txt *.class