[ad name=”AD_INBETWEEN_POST”] Let us see how to create a JAR file using Java’s jar command as well as using Eclipse IDE. The JAR file format is based on the popular ZIP file format. Usually these file are used for archiving and distribution the files and implementing various libraries, components and plug-ins in java applications. Compiler and JVMs (Java Virtual Machine) can understand and implement these formats for java application.
JAR file using Java commandsFollowing are few commands that can be used to create/view/modify/execute a JAR file using Java command line utilities and JVM.
Create a JAR file
jar cf JAR_FILE_NAME FILE_NAMES_OR_DIRECTORY_NAME e.g. jar cf MyApp1.jar C:\JavaProject\MyApp
View contents of a JAR file
jar tf JAR_FILE_NAME e.g. jar tf MyApp1.jar
View contents with detail of a JAR file
Note that we have used v (verbose) option to see the detail of JAR.
jar tvf JAR_FILE_NAME e.g. jar tvf MyApp1.jar
Extract content of JAR file
jar xf JAR_FILE_NAME e.g. jar xf MyApp1.jar
Extract specific file from JAR file
jar xf JAR_FILE_NAME FILE_NAME(S)_FROM_JAR_FILE e.g. jar xf MyApp1.jar Test1.class
Update a JAR file
jar uf JAR_FILE_NAME FILE_NAMES_FROM_JAR_FILE e.g. jar uf MyApp1.jar Test1.class
Executing a JAR file
java -jar JAR_FILE_NAME e.g. java -jar MyApp.jar
Create an executable JAR fileIn order to create an executable JAR, one of the classes that we include in our JAR must be a main class. Create a text file called MANIFEST.MF using any text editor and copy following content in it.
Where MyMainClass is the name of the class that contents main method. Also note that you have to specify fully qualified class name here. Use following command to create an executable JAR file.
Manifest-Version: 1.0 Main-Class: MyMainClass
jar cvfm MyApp.jar MANIFEST.MF FILE_NAMES_OR_DIRECTORY_NAME