Working with Archive Files - Beginning Java 8 Language Features - page 378

Note that when you specify the option m , you must also specify the manifest file name. The order in which you
specify the new JAR file name and the manifest file name must match the order of options m and f . For example, you
can change the above command by specifying the f and m options in a different order as follows:
jar cmf manifest.txt test.jar *.class
This command will add a manifest file with the following contents to the test.jar file:
Manifest-Version: 1.0
Created-By: 1.8.0_20-ea (Oracle Corporation)
Main-Class: com.jdojo.intro.Welcome
If you do not specify the Manifest-Version and Created-By attribute in your manifest file, the tool adds them. It
defaults the Manifest-Version to 1.0. The Created-By is defaulted to the JDK version you use.
You have been running a Java program by using the java command and specifying the class name that has the
main() method as follows:
java com.jdojo.intro.Welcome
You can also run a jar file using the -jar option with the java command as follows:
java -jar test.jar
When you run the above command, the JVM will look for the value of the Main-Class attribute in the
MANIFEST.MF file in the test.jar file and attempt to run that class. If you have not included a Main-Class attribute in
the test.jar file, the above command will generate an error.
You can also add the Main-Class attribute value in the manifest file without creating your own manifest file. Use
the option e with the jar tool when you create/update a jar file. The following command will add com.jdojo.intro.
Welcome as the value of the Main-Class in the MANIFEST.MF file in the test.jar file:
jar cfe test.jar com.jdojo.intro.Welcome *.class
The following command will add com.jdojo.intro.Welcome as the value of the Main-Class in the MANIFEST.MF
file in an existing test.jar file by using the option u for update:
jar ufe test.jar com.jdojo.intro.Welcome
You can set the CLASSPATH for a JAR file in its manifest file. The attribute name is called Class-Path , which you
must specify in a custom manifest file. It is a space-separated list of jar files, zip files, and directories. The Class-Path
attribute in a manifest file looks like
Class-Path: chapter8.jar file:/c:/book/ http://www.jdojo.com/jutil.jar
The above entry has three items for the CLASSPATH: a JAR file chapter8.jar , a directory using the file protocol
file:/c:/book/ , and another JAR file using a HTTP protocol http://www.jdojo.com/jutil.jar . Note that a
directory name must end with a forward slash. Suppose this Class-Path setting is included in the manifest file for the
test.jar file. When you run the test.jar file using the following java command, this CLASSPATH will be used to
search and load classes.
java -jar test.jar