Objectives:1. Archiving and Packaging Java Code 2. The jar Program 3. Example Applet JAR Files

 JAR file archives provide packaging for applications, applets, & JavaBeans  Multiple classes can be packaged in JAR files  JAR Files specified within HTML  Manifest file  JAR files use ZIP compression format

JAR Files:  provide a delivery mechanism for JavaBeans, packaging all the necessary resources together in a single file. Multiple Beans may be contained in a single JAR file, and the file may also contain an optional manifest which lists the contents.  help transport Beans over the Internet in easy-to- manage packages, and they are also used to archive applets for more efficient downloading performance.

The jar Utility  Creates JAR files  Adds to existing archives  Extracts items in an archive  Lists archive contents  Syntax: jar {ctux} [vfm0M] [jar-file] [manifest-file] files

jar Command jar {ctux} [vfm0M] [jar-file] [manifest-file] files  jar-file specifies the name of the archive file. No required naming conventions exist for Java archive files, although you will most likely see the file extension.jar associated with them.  The manifest-file argument is a file containing a list of the jar file contents. A manifest file is required when using the m command line option. More...

jar Command jar {ctux} [vfm0M] [jar-file] [manifest-file] files  files to be archived are listed at the end of the command and are separated by whitespace.  Wildcard characters are accepted  directory names are followed recursively, i.e., all files in subdirectories will also be archived.  File names are relative to the directory from which you run the jar command  special –C option introduced in Java 1.2 to change the relative directory.  forward or backward slashes are accepted, making the jar command operating-system independent.

jar command line options Only one of the following c: Create a new archive file t: List the table of contents for the archive file u: Update the contents of the archive or manifest x: Extract named files (or all) from the archive Other options can be combined or omitted v: Verbose output f: Specify [jar-file] m: Include information from [manifest-file] 0: Do not use compression M: Do not create a manifest file for the archive entries

Examples of jar command  Create an archive called Simulator.jar that contained the single class Machine.class  jar cf Simulator.jar Machine.class  List the table of contents of Simulator.jar using verbose output  jar tvf Simulator.jar  Extract all contents of Simulator.jar  jar xvf Simulator.jar

JAR Files & HTML Improve Applet download performance  compression of JAR files allows efficient downloading of applets over the Web.  entire archive may be downloaded in a single HTTP transaction.  avoids reconnect each time a specific.class file or resource is needed. ARCHIVE Tag  filename is relative to the location of the HTML page.  still need a CODE tag to indicate which class within the archive starts the applet.

The Manifest The manifest file exists to provide information about the contents of its associated jar file.  Automatically created  if not specified otherwise, named manifest.mf  placed in the archive under a directory called /META-INF  M option in jar command suppresses creation.  Lists the entries in the archive  First entry identifies manifest version Example: Manifest-Version: 1.0 Created-By: (Sun Microsystems Inc.)  applies to the entire JAR file

Manifest Contents  Subsequent sections must begin with  Name:  describe individual elements JavaBeans, files, packages, and URLs.  Each section of the manifest file refers to an entry in the archive and is separated by a blank line.  Attribute-value pairs of the format attribute: value are used in each section to give information about that particular entry. Name: Calculator.class lines describing this file Name: edu/weber/mypkg lines describing this package

Manifest Contents  Attribute/Value pairs  Note Java-Bean attribute in example: Name: StockBroker/Simulator/Stock.class Digest-Algorithms: MD5 SHA MD5-Digest: wuXrtYN-56Nn4rtDFewq=-tr SHA-Digest: fg67tKdkfR65-SRkdrslegvY-tyK Java-Bean: True

Custom Manifest File Indicating Beans Manifest-Version: 1.0 Name: StockBroker/Simulator/Stock.class Java-Bean: True Name: StockBroker/Simulator/Helper.class Java-Bean: False Name: StockBroker/Simulator/Price.class Java-Bean: True

Creating the Archive File  create an archive file with a customized manifest file by using both the m and f options and giving the required arguments as shown in the slide. The generated manifest.mf file in the archive should have the information given in Simulator.mf (which you write). > jar cfm Simulator.jar Simulator.mf StockBroker/Simulator/Stock.class StockBroker/Simulator/Helper.class StockBroker/Simulator/Price.class  if the jar options contain both the letters f and m, the JAR and manifest files listed in the command line should be in the same order. For example, if f comes before m, the JAR filename should come before the manifest filename.

Examples See Composites using a jar at: jar contains three classes  ButtonPanel.class  RadioPanel.class  Test1.class(code; this class is used to start applet) See Animation Demo using a jar at:  inner classes specified in a manifest