Executable Jars

1
Executable Jars

• Dan Fleck
• Fall 2007

2
Introduction

• Executable Jars allow a program to be packaged
  and run more simply
• Todays Agenda
• How to run Java Programs
• How to Create Executable Jars

3
How to Run Java Programs

• Assume we are in directory
• C\javacode\myprojects\cls
• Contents of that directory are

MyClass.class Shape.class Ball.class
edu\
Utils.class Elephant.class
gmu\
Ball.jpg Elephant.jpg Sphere.gif
pack1\
pack2\
images\
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How to Run Java Programs
C\javacode\myproject\cls\
edu
gmu

• Run using the classes cd to directoryC\javacode
  \myprojects\clsjava edu.gmu.pack1.MyClass
• Run using the classpathjava -cp
  c/javacode/myproject/cls edu.gmu.pack1.MyCl
  ass
• Run using the the Jarjava -cp myjar.jar
  edu.gmu.pack1.MyClass
• Run using an executable Jarjava -jar
  myexecutablejar.jar

pack1
pack2
images
Executable Jars are the easiest! (Less thinking!)
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How to Create a Jar
C\javacode\myproject\cls\
edu
gmu
pack1

• cd to the top level directory of your package.
  (c\javacode\myproject\cls)
• Create itjar cvf myjar.jar c create new
  archivev verbose outputf archive file name
• Check it!jar tvf myjar.jart display table of
  contents

pack2
images
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How to Create a Jar
C\javacode\myproject\cls\
edu
gmu
pack1

• Try running it!java -cp myjar.jar
  edu.gmu.pack1.MyClass

pack2
images
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Question
C\javacode\myproject\cls\
edu
gmu
pack1

• Question What did java need to know in order to
  run the program?
• java -cp myjar.jar edu.gmu.pack1.MyClass
• Answer Which class is the main-class!java -cp
  myjar.jar edu.gmu.pack1.MyClass

pack2
images
An executable Jar just needs to know the
main-class in order to run!
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Creating the executable jar
C\javacode\myproject\cls\
edu
gmu
pack1

• cd to the top level directory of your package.
  (c\javacode\myproject\cls)
• Create a manifest text file that holds the
  main-class Notepad mymanifest Manifest-Version
  1.0 Main-Class edu.gmu.pack1.MyClass
• Create the jar with -m optionJar cvfm myjar.jar
  mymanifest m use specified manifest

pack2
images
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Creating the executable jar
C\javacode\myproject\cls\
edu
gmu
pack1

• Test it
• java -jar myjar.jar

pack2
images
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Advantages

• Jars make code more portable by keeping it all
  together
• Executable jars make the code easier to
  runNote On some systems (Windows, some Unix
  variants) Jar files are associated with the java
  -jar command, so simply double-clicking on an
  executable Jar will run it.