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
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.
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:
coption indicates that you want to create a JAR file.
moption indicates that you want to merge information from an existing file into the manifest file of the JAR file you're creating.
foption indicates that you want the output to go to a file (the JAR file you're creating) rather than to standard output.
manifest\-additionis the name (or path and name) of the existing text file whose contents you want to add to the contents of JAR file's manifest.
jar\-fileis the name that you want the resulting JAR file to have.
input\-file\(s\)argument is a space-separated list of one or more files that you want to be placed in your JAR file.
f options must be in the same order as the corresponding arguments.
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.