Packaging Programs in JAR Files

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Trail: Deployment

Lesson: Packaging Programs in JAR Files

This chapter has been updated to reflect features and conventions of the latest release, JDK 5.0. If you notice any errors or omissions (or something you really like), please tell us.

and JavaMail are examples of extensions developed by Sun^TM. By using the JAR file format, you can turn your software into extensions as well.
Package Sealing: Packages stored in JAR files can be optionally sealed so that the package can enforce version consistency. Sealing a package within a JAR file means that all classes defined in that package must be found in the same JAR file.
Package Versioning: A JAR file can hold data about the files it contains, such as vendor and version information.
Portability: The mechanism for handling JAR files is a standard part of the Java platform's core API.
This lesson has four sections:

Using JAR Files: The Basics

This section shows you how to perform basic JAR-file operations, and how to run software that is bundled in JAR files.

Working with Manifest Files: The Basics

This section explains manifest files and how to customize them so you can do such things as seal packages and set an application's entry point.

Signing and Verifying JAR Files

This section shows you how to digitally sign JAR files and verify the signatures of signed JAR files.

Using JAR-related APIs

This section introduces you to some of the JAR-handling features of the Java platform. The JAR file format is an important part of the Java platform's extension mechanism. You can learn more about that aspect of JAR files in the The Extension Mechanism trail of this tutorial.

Additional References

The documenation for the Java Development Kit includes information about the Jar tool:

Java Archive (JAR) Files Guide
JAR File Specification

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