Modifying a Manifest File
Trail: Deployment
Lesson: Packaging Programs in JAR Files
Section: Working with Manifest Files: The Basics

Modifying a Manifest File

You use the m command-line option to add custom information to the manifest during creation of a JAR file. This section describes the m option.

The Jar tool automatically puts a default manifest with the pathname META-INF/MANIFEST.MF into any JAR file you create. You can enable special JAR file functionality, such as package sealing, by modifying the default manifest. Typically, modifying the default manifest involves adding special-purpose headers to the manifest that allow the JAR file to perform a particular desired function.

To modify the manifest, you must first prepare a text file containing the information you wish to add to the manifest. You then use the Jar tool's m option to add the information in your file to the manifest.

Warning: The text file from which you are creating the manifest must end with a new line or carriage return. The last line will not be parsed properly if it does not end with a new line or carriage return.

The basic command has this format:

jar cfm jar-file manifest-addition input-file(s)

Let's look at the options and arguments used in this command:

The m and f options must be in the same order as the corresponding arguments.

Note: The contents of the manifest must be encoded in UTF-8.

The remaining sections of this lesson demonstrate specific modifications you may want to make to the manifest file.

Previous page: Understanding the Default Manifest
Next page: Setting an Application's Entry Point