Managing JAR Files with WinZIP

<< 'jar' - The JAR File Tool

<< Java Tool Tutorials - Herong's Tutorial Notes

This section provides a tutorial example on how to manage a JAR file as a ZIP file with the ZIP tool, WinZIP.

The JAR specification says that "JAR file is a file format based on the popular ZIP file format". So are JAR files really ZIP files? Let's do some tests to find out.

Test 1. Create a JAR file, test.jar, with "jar" command. Rename test.jar to test.zip. Unzip test.zip with WinZIP. You should have no problem to extract all files out of test.zip with WinZIP.

Test 2. Create a ZIP file, tutu.zip, with WinZIP. Rename tutu.zip to tutu.jar. Extract files from tutu.jar with "jar". You should have no problem to extract all files out of tutu.jar with "jar" command.

Test 3. Create a password protected ZIP file, secure.zip, with WinZIP. Rename secure.zip to secure.jar. Extract files from secure.jar with "jar". You should get a run time exception like this:

C:\herong>jar tf secure.jar
java.io.FileNotFoundException: secure.jar (The system cannot find the
   file specified)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(FileInputStream.java:106)
        at java.io.FileInputStream.<init>(FileInputStream.java:66)
        at sun.tools.jar.Main.run(Main.java:185)
        at sun.tools.jar.Main.main(Main.java:904)

So JAR files and ZIP files are fully compatible, as long as no encryptions are used on ZIP files.

I guess I don't need WinZIP anymore.

Sections in This Chapter

JAR - Java Archive File Format

'jar' - JAR File Tool Command and Options

Creating the First JAR File - hello.jar

Managing JAR Files with WinZIP

META-INF/MANIFEST.MF - JAR Manifest File

Adding META-INF/MANIFEST.MF to JAR Files

Using JAR Files in Java Class Paths

Creating Executable JAR Files