Lesson: Packaging Programs in JAR Files课程：在JAR文件中打包程序

The Java™ Archive (JAR) file format enables you to bundle multiple files into a single archive file.Java™归档（JAR）文件格式使您能够将多个文件捆绑到单个归档文件中。Typically a JAR file contains the class files and auxiliary resources associated with applets and applications.通常，JAR文件包含与小程序和应用程序关联的类文件和辅助资源。

The JAR file format provides many benefits:JAR文件格式提供了许多好处：

• Security安全性: You can digitally sign the contents of a JAR file.：您可以对JAR文件的内容进行数字签名。Users who recognize your signature can then optionally grant your software security privileges it wouldn't otherwise have.识别您的签名的用户可以选择授予您的软件安全特权，否则它将不会拥有这些特权。
• Decreased download time减少下载时间: If your applet is bundled in a JAR file, the applet's class files and associated resources can be downloaded to a browser in a single HTTP transaction without the need for opening a new connection for each file.：如果小程序捆绑在JAR文件中，则小程序的类文件和相关资源可以在单个HTTP事务中下载到浏览器，而无需为每个文件打开新连接。
• Compression压缩: The JAR format allows you to compress your files for efficient storage.：JAR格式允许您压缩文件以实现高效存储。
• Packaging for extensions扩展的打包: The extensions framework provides a means by which you can add functionality to the Java core platform, and the JAR file format defines the packaging for extensions.：扩展框架提供了一种向Java核心平台添加功能的方法，JAR文件格式定义了扩展的打包。By using the JAR file format, you can turn your software into extensions as well.通过使用JAR文件格式，您还可以将软件转换为扩展名。
• Package Sealing包装密封: Packages stored in JAR files can be optionally sealed so that the package can enforce version consistency.：存储在JAR文件中的包可以选择性地密封，以便包可以强制实现版本一致性。Sealing a package within a JAR file means that all classes defined in that package must be found in the same JAR file.在JAR文件中密封一个包意味着该包中定义的所有类都必须在同一个JAR文件中找到。
• Package Versioning包版本控制: A JAR file can hold data about the files it contains, such as vendor and version information.：JAR文件可以保存有关其包含的文件的数据，例如供应商和版本信息。
• Portability便携性: The mechanism for handling JAR files is a standard part of the Java platform's core API.：处理JAR文件的机制是Java平台核心API的标准部分。

This lesson has four sections:本课程分为四节：

Using JAR Files: The Basics使用JAR文件：基础

This section shows you how to perform basic JAR-file operations, and how to run software that is bundled in JAR files.本节介绍如何执行基本的JAR文件操作，以及如何运行打包在JAR文件中的软件。

Working with Manifest Files: The Basics使用清单文件：基础

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.本节介绍清单文件以及如何自定义它们，以便您可以执行诸如密封包和设置应用程序入口点之类的操作。

Signing and Verifying JAR FilesJAR文件的签名和验证

This section shows you how to digitally sign JAR files and verify the signatures of signed JAR files.本节介绍如何对JAR文件进行数字签名，并验证已签名JAR文件的签名。

Using JAR-related APIs使用与JAR相关的API

This section introduces you to some of the JAR-handling features of the Java platform.本节向您介绍Java平台的一些JAR处理特性。The JAR file format is an important part of the Java platform's extension mechanism.JAR文件格式是Java平台扩展机制的重要组成部分。You can learn more about that aspect of JAR files in the The Extension Mechanism trail of this tutorial.您可以在本教程的扩展机制教程中了解有关JAR文件这方面的更多信息。

Questions and Exercises: JAR问题和练习：JAR

Test what you've learned about JAR.测试您对JAR的了解。

Additional References其他参考资料

The documentation for the Java Development Kit (JDK) includes information about the Jar tool:Java开发工具包（JDK）的文档包括关于Jar工具的信息：

• Java Archive (JAR) Files GuideJava存档（JAR）文件指南
• JAR File SpecificationJAR文件规范