Sets the file specified by the jarfile operand to be the name of the JAR file that is created ( c), updated ( u), extracted ( x) from, or viewed ( t). The ambiguity leads to an error and the jar command creation or update operation is terminated. Specifying both m and e options together when a particular manifest also contains the Main-Class attribute results in an ambiguous Main-Class specification. Jar -cfe Main.jar mydir.Main mydir/Main.class Jar -cfe Main.jar mydir/Main mydir/Main.class For example, if Main.class is in a package called mydir, then the entry point can be specified in one of the following ways: If the entry point class name is in a package, then it could use either the dot (.) or slash (/) as the delimiter. The Java Runtime Environment (JRE) can directly call this application by running the following command: The e option can be used when creating ( c) or updating ( u) the JAR file.įor example, the following command creates the Main.jar archive with the Main.class file where the Main-Class attribute value in the manifest is set to Main: The use of this option creates or overrides the Main-Class attribute value in the manifest file. Sets the class specified by the entrypoint operand to be the entry point for a standalone Java application bundled into an executable JAR file. Use the following options to customize how the JAR file is created, updated, extracted, or viewed: e Other arguments are either options that modify the behavior of the operation, or operands required to perform the operation. It has several operation modes, defined by one of the mandatory operation arguments. The syntax for the jar command resembles the syntax for the tar command. A JAR file can be used as a class path entry, whether or not it is compressed.
The jar command also allows individual entries in a file to be signed by the applet author so that their origin can be authenticated. The jar command also compresses files, which further improves download time. This dramatically improves download times. When the components of an applet or 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.
However, the jar command was designed mainly to package Java applets or applications into a single archive. The jar command is a general-purpose archiving and compression tool, based on ZIP and the ZLIB compression format.
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