Run a JAR file from the command line and specify classpath

Question

I ve compiled a JAR file and specified the Main-Class in the manifest  I used the Eclipse Export function   My dependencies are all in a directory labeled lib  I can t seem to get a straight answer on how to execute my JAR file while specifying it should use the lib   as the classpath   I ve tried      java -jar -cp   lib   MyJar jar    java -cp   lib   -jar MyJar jar    java -cp   lib   com somepackage subpackage Main   etc     Each gives an error saying      Error  Could not find or load main class        or gives the NoClassDefFoundError indicating the libraries are not being found   I even tried remaking the JAR file and included the lib directory and contents  but still no dice     How can I execute a JAR file from the command line and specify the classpath to use

User · Answer

Run a jar file and specify a class path like this:

java -cp <jar_name.jar:libs/*> com.test.App

jar_name.jar is the full name of the JAR you want to execute

libs/* is a path to your dependency JARs

com.test.App is the fully qualified name of the class from the JAR that has the main(String[]) method

The jar and dependent jar should have execute permissions.

User · Answer

You can do these in unix shell   java -cp MyJar jar lib   com somepackage subpackage Main   You can do these in windows powershell   java -cp  MyJar jar lib    com somepackage subpackage Main

User · Answer

When you specify -jar then the -cp parameter will be ignored    From the documentation      When you use this option  the JAR file is the source of all user classes  and other user class path settings are ignored     You also cannot  include  needed jar files into another jar file  you would need to extract their contents and put the  class files into your jar file   You have two options    include all jar files from the lib directory into the manifest  you can use relative paths there  Specify everything  including your jar  on the commandline using -cp   java -cp MyJar jar lib   com somepackage subpackage Main

User · Answer

Alternatively  use the manifest to specify the class-path and main-class if you like  so then you don t need to use -cp or specify the main class   In your case it would contain lines like this   Main-Class  com test App Class-Path  lib one jar lib two jar   Unfortunately you need to spell out each jar in the manifest  not a biggie as you only do once  and you can use a script to build the file or use a build tool like ANT or Maven or Gradle    And the reference has to be a relative or absolute directory to where you run the java -jar MyJar jar   Then execute it with  java -jar MyJar jar

User · Answer

You can do a Runtime getRuntime exec command  to relaunch the jar including classpath with args

[java] Run a JAR file from the command line and specify classpath

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