Thread: Creating a jar File

Originally Posted by skate101

i can only make Runnable Jar without the required JAR by using this command

jar cvfm Test.jar manifest.txt package/*.class

External jars must be declared into the manifest. The manifest should have a line like:

Class-Path: lib/other1.jar lib/other2.jar

The "lib" sub folder is just an example. Other jars must be tied with a relative path to your main jar.

And note: if you write the manifest yourself, beware about the line length limitation, from jar specs:

No line may be longer than 72 bytes (not characters), in its UTF8-encoded form. If a value would make the initial line longer than this, it should be continued on extra lines (each starting with a single SPACE)

Originally Posted by skate101

when i executed this command:

jar cvfm ./bin/Skate.jar ./manifest/Manifest.txt ./classes/* ./lib/*

First: it has no sense (and it's useless) that you put external jars into your jar. The JVM will not search jars into your jar!

Originally Posted by skate101

it created the Skate.jar inside the bin directory but when i execute the jar, it throws an exception

Exception in thread "main" java.lang.NoClassDefFoundError:

i understand that java cannot find the entry point because in theManifest file i declared the entry point like this

Main-Class: com.main.Main

and when i checked the Skate.jar, i noticed the "classes" directory are also bundle with the Skate.jar

It's not correct that the jar contains the 'classes' directory. If you have a class com.main.Main, the jar must contain a "com" folder at the root of the jar (the "com" contains a "main" folder, etc...).

Use the -C option of jar tool (see official documentation for further informations).
Instead to use:

./classes/*

use:

-C ./classes .


Final note: if you want to keep the relation
....anything/bin/yourjar
....anything/lib/otherjars

then the Class-Path entry in your manifest must be like:

Class-Path: ../lib/xyz1.jar ../lib/xyz2.jar

because the JVM must know to go "up" (..) and then enter into lib folder to find the jar.

Originally Posted by skate101

Is there a way in creating a RUNNABLE jar via Command prompt be like the way how the ECLIPSE IDE exports its RUNNABLE JAR package with the dependency JARS. ?

Eclipse has a "Fat Jar" plugin that can create a jar containing your classes/resources and all classes/resources from all dependencies.
Technically it's possible to do this from command prompt but requires "some" work: a) first, you need to unpack (unzip) all required jars somewhere, b) you need to "pull in" all those classes/resources using that same -C command that now you know.

However having a single jar with all classes/resources from all dependencies is not a good thing, and at least for 2 reasons:
1) Licensing problems: the producer of a library could disagree about this type of bundling for any reason.
2) Update/deploy problems: if you change just only a small thing in your application, you need to recreate this big jar. This may not be a big problem for you. But if the application is deployed through internet (e.g. you send the jar to a customer, or there is an automatic update system, or you store it with FTP somewhere) the big size may be a problem.
And if a dependency need to be updated (e.g. you choose another version) you need to redo the a) step for this library.

So please, don't do this.