include external jar when running java -jar

Question

From my readings, when you execute a command as follows:

java -jar foo.jar

Then the main classpath is ignored and the classpath is taken from the manifest file.

Further, the classpath declared on the command line is also ignored. So in:

java -classpath /usr/local/jar/foobar.jar -jar foo.jar

/usr/local/jar/foobar.jar is ignored.

Lastly, I have read that the manifest file can only only contain relative paths, within the jar file.

So, how do you include absolute paths to external jars, that are present on the system, but not in the jar file being executed?

Answer 1

You can create a folder, say lib, within the folder where you have the jar file.

Manifest.MF contents can be:

Main-Class: com.mastergaurav.test.app.MainClass
Class-Path: lib/one.jar lib/two.jar

Folder contents:

mainFolder/
   * lib/one.jar
   * lib/two.jar
   * my-main.jar

To execute:

java -jar my-main.jar

Answer 2

Is there a reason why you are avoiding invoking the main class like

java -cp /usr/local/jar/foobar.jar:/some/other/path.jar com.your.main.classname

?

This type of invocation allows you to mix absolute paths with relative paths. Put this into a shell script or batch file to avoid having to actually type or remember the full classpath to simplify things.