How to create a .jar file using the terminal

Question

I'm trying to create a .jar file using the mac terminal but am having bit of trouble. I followed the steps here but was unsuccessful. I got this error message:

Failed to load Main-Class manifest attribute from
aclient.jar

So how exactly do you go about doing it? My java program is called Main.java and I have compiled it into a .class file. Now what do I do?

Thanks

Answer 1

1) Ensure that all necessary files are within the directory, you have opened a terminal/Command Prompt and have navigated to that directory.

2) Compile the .java class, for example HelloWorld.java with

javac HelloWorld.java

3) This will produce a .class file needed for the JAR file.

4) Next create a manifest file (saved using the extension .txt) using the text editor and input the following

Main-Class: HelloWorld

or whatever your file's name is.

5) Next create the JAR file using this code:

jar cfm HelloWorld.jar Manifest.txt HelloWorld.class

6) Run the file:

java -jar HelloWorld.jar

If anything seems unclear consult these websites: creating a jar file and setting an applications entry point.

Hope this helps others, cheers Tom!

Edit:

Following inga's comment it's worth noting that in order to include multiple files in the jar you need to use the:

javac *.java

followed by

jar cfm HelloWorld.jar Manifest.txt *.class

Answer 2

Yes, we need to use new line at the end of class name... It worked for me

i.e. Main-Class: HelloWorld

 It will look like this in Notepad++
 1.Main-Class: HelloWorld
 2.

Answer 3

Maybe this will help re Manifest.txt file:

Warning: The text file must end with a new line or carriage return. The last line will not be parsed properly if it does not end with a new line or carriage return.

Answer 4

You need to have an text file that defines the main class. E.g.

% cat MyMain
Main-Class: HelloWorld

then

%jar cvfm foo.jar MyMain *.class
%java -jar foo.jar
Hello world 

See: http://java.sun.com/j2se/1.4.2/runtime.html#example.

Answer 5

I followed the instructions and was getting issue while loading the Manifest.txt file.

In Manifest.txt we just simply need to write Main-class: class_name

But after above statement please press enter in Manifest.txt and your Manifest.txt load issue will be resolved. New line at the end of Manifest file is required.

Regards