Operation Modifiers Valid Only in Create and Update Modes Sends or prints verbose output to standard output. It will then look in directories with successively lower VERSION numbers, and finally look in the root of the JAR. Places all files specified after the option into a versioned directory of the JAR file named META-INF/versions/ VERSION/, where VERSION must be must be a positive integer whose value is 9 or greater.Īt run time, where more than one version of a class exists in the JAR, the JDK will use the first one it finds, searching initially in the directory tree whose VERSION number matches the JDK's major version number. release VERSIONĬreates a multirelease JAR file. You can use the following options to customize the actions of any operation mode included in the jar command.Ĭhanges the specified directory and includes the files specified at the end of the command line.
The following operations described in Operation Modifiers Valid Only in Create and Update Modes are valid only when creating or updating a modular JAR or updating an existing non-modular JAR: A JAR file can be used as a class path entry, whether or not it’s compressed.Īn archive becomes a modular JAR when you include a module descriptor, module-info.class, in the root of the given directories or in the root of the JAR archive. The jar command also enables individual entries in a file to be signed so that their origin can be authenticated. The jar command also compresses files, which further improves download time. This dramatically improves download times. When modules or the components of an application (files, images, and sounds) are combined into a single archive, they can be downloaded by a Java agent (such as a browser) in a single HTTP transaction, rather than requiring a new connection for each piece. Other arguments are either options that modify the behavior of the operation or are required to perform the operation. It has several main operation modes, defined by one of the mandatory operation arguments. The syntax for the jar command resembles the syntax for the tar command. For transportation and deployment, it’s usually more convenient to package modules as modular JARs.
Initially, the jar command was designed to package Java applets (not supported since JDK 11) or applications however, beginning with JDK 9, users can use the jar command to create modular JARs. The jar command is a general-purpose archiving and compression tool, based on the ZIP and ZLIB compression formats.
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