Packaging Java software

1. Packaging Java software

2. What the problem is • An executable program often consists of a very large number of files • It's a nuisance to manage lots of files • We like to "package" files into a single file for transportation and distribution • We will explore several different packaging techniques • Different techniques are suitable for different situations and kinds of programs

3. Zip files • Zip files are • convenient single archive files • compressed to save space • understood on all platforms • Most Windows users have probably used WinZip to unpack downloaded files • Fewer people have used WinZip to create zip files

4. Creating a .zip file, I • To create a .zip file, use WinZip Classic

5. Creating a .zip file, II • The WinZip Classic interface is easy to figure out • Create a new archive • Add files to it

6. jar files • A jar (Java archive) file is like a zip file • jar files were designed for Java, but can be used for any kind of files • The jar program is modeled after the UNIX tar program and works very much like it • tar originally stood for tape archive • jar files are particularly important for Applets • An <applet> tag can request a jar archive

7. Applets • Here's how an Applet gets loaded: • First, the browser requests the .html page containing the Applet • The <applet code="MyApplet.class" ...> tag causes the browser to request the file MyApplet.class • The browser's Java VM looks at this file and makes requests for other .class files that may be needed • The applet starts and requests image and sound files • All this two-way communication takes time • Applets load faster if they make fewer requests

8. Too many files • A complete Java Applet may consist of • many .class files • many .gif and/or .jpg files • possibly some .avi or .mp3 files • other file types may be included • My most complex "animation" applet uses: • One .html file • Four .class files • Fifty .jpg files

9. Creating a jar file • Example command: jar cvf arch.jar *.class • cvf is a list of options • c -- create a jar file • v -- verbose; tell what you do as you do it • f -- use this jar file (almost always needed!) • arch.jar is the name of the file that is created • You don't need the .jar extension, but it's a good idea • *.class says to include all class files • You can list additional files at the end

10. Unpacking a jar file • Example command: jar xvf arch.jar • cvf is a list of options • x -- extract from a jar file • v -- verbose; tell what you do as you do it • f -- use this jar file (almost always needed!) • arch.jar is the name of the file that is unpacked • You will also get a "manifest" file that may contain information about the jar file • Most of the time you can ignore the manifest file

11. Examining a jar file • Example command: jar tvf arch.jar • cvf is a list of options • t -- tell what is in the jar file • v -- verbose; tell what you do as you do it • f -- use this jar file (almost always needed!) • arch.jar is the name of the file that is examined

12. Using a jar file in an Applet • An applet must be used from an HTML page • The Applet tag has three required parameters: • code = the name of the main class file • height =, width = the size of the applet • To use a jar file, we need a fourth parameter: • archive = name of the jar file • Example: • <applet height="400" width="500" code="TestEngine.class" archive="lispquiz.jar">

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14. The End