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Executable JAR ignores its own Class-Path attribute

I used the instructions found in Maven - how can I add an arbitrary entry to the Class-Path path to the bank to add an arbitrary entry to the Class-Path attribute. Here is my MANIFEST.MF file:

 Manifest-Version: 1.0 Class-Path: jace-runtime.jar Main-Class: org.jace.examples.Test

I defined org.jace.examples.Test as follows:

 public class Test { public static void main(String[] args) { System.out.println("classpath: " + System.getProperty("java.class.path")); System.out.println("PeerExample: " + Class.forName("org.jace.util.ShutdownHook")); } }

where org.jace.util.ShutdownHook defined in jace-runtime.jar . When I java -jar peer_example1.jar I get the following output:

classpath: peer_example1.jar Exception in thread "main" java.lang.ClassNotFoundException: org.jace.util.ShutdownHook

In other words, Java adds the JAR executable in Class-Path to classes, but ignores Class-Path to classes. If I java -cp jace-runtime.jar;peer_example1.jar org.jace.examples.Test I get the expected result:

classpath: jace-runtime.jar;peer_example1.jar

Any ideas?

+12
java classpath jar
May 03 '12 at 17:34
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3 answers

Answering my own question:

  • Adding custom records to Class-Path is fine. The problem occurs when you enable JAR indexing with:

     <configuration> <archive> <index>true</index> </archive> </configuration>

    Maven will omit your entries from META-INF/INDEX.LIST .

  • When you use the JAR at runtime, Java will look for INDEX.LIST to search for classes, not MANIFEST.MF.

  • Since your entries are not in INDEX.LIST, they will not be found by the class loader, no matter what the manifest says.

A simple workaround is to disable JAR indexing. I'm not sure how to introduce an arbitrary Class-Path with indexing.

+15
May 03 '12 at 18:19
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For those who otherwise might not know, the executable archive mechanism takes the manifest class path and uses it to load external classes into the archive.

So, if you expect a WAR with an explicit WEB-INF / classes class class to find the classes in the WEB-INF / classes entry inside , then you will be disappointed.

0
Jan 05 '14 at 23:05
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On tooldocs page for jar option - Link to documents

When you use this parameter, the JAR file is the source of all user classes, and other parameters of the user class path are ignored.

-four
May 03 '12 at 17:59
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