How to Execute a JAR File with Additional Classpath Options?

Calling "java -jar MyFile.jar" with Additional Classpath Option

When executing a JAR file with the command "java -jar MyFile.jar", it's essential to understand the classpath requirements. The "-jar" option signifies that the JAR file contains the main class to be executed, while "-cp" is used for specifying an additional classpath.

In the given scenario, the error encountered is likely due to the combination of "-jar" and "-cp" options. As the answer explains, these options are mutually exclusive. Using both options simultaneously results in an ambiguous command that Java cannot interpret.

To resolve the issue, the user has two options:

• Option 1: Use the Manifest-Class-Path Attribute:

  In this approach, the JAR file's manifest includes the "Class-Path" attribute, which specifies the required JARs on the classpath. This eliminates the need for the "-cp" option.

• Option 2: Specify the Full Classpath with "-cp":

  For this option, the command would be "java -cp 'MyProgram.jar:libs/*' main.Main". Here, the "-cp" specifies the full classpath, including the main JAR and its dependencies, while the explicit naming of the "main.Main" class ensures that it runs as the entry point.

Alternatively, Ant can be leveraged. For the "manifest approach", the "" task adds dependencies to the manifest before creating the JAR.

On the other hand, for the "classpath approach", the full classpath is specified using the "-cp" option in conjunction with the JAR file and explicit naming of the main class. This method is suitable if the target environment will not recognize the manifest's "Class-Path" attribute.

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