OpenJDK 8 jar tool customizing Manifest file inside jar

Solution Verified - Updated

Environment

  • OpenJDK 8

Issue

How to add custom details, such as Manifest version, OpenJDK version, and Class Path details on the manifest file?

Resolution

The example below creates a ClientJar.jar file, which has a custom manifest file: Manifest.txt, with all details to be overwriting on the manifest file.

$ cat Manifest.txt 
Manifest-Version: 37.0
Created-By: 1.7.0_237 (Example Corp) <---------------- example
Class-Path: lib/jboss-client.jar lib/EjbPrint.jar lib/jsse.jar <------------- adding jar libraries to class path
Sealed: true <------- cannot be opened
Main-Class: StandaloneClient <--------- sets main class when executing java -jar ClientJar.jar

And to compile one can overwrite it with the option "m" as below:

$jar cvfm ClientJar.jar Manifest.txt StandaloneClient.class -C lib . wildfly-config.xml

The option below writes the class StandaloneClient as the main class in the manifest file:

$JAVA_HOME/bin/jar cvfe ClientJar.jar StandaloneClient StandaloneClient.class

Root Cause

Manifest.MF contains information about the files contained in the JAR file and when a JAR file is created a default one is crated inside META-INF folder. It contain a list key-pair of information about the build, jdk version, which application that built it:

ValueMeaning
Manifest-Version: 1.0Manifest version
Archiver-Version: Plexus ArchiverArchiver version
Created-By: Apache Maven 3.6.0Maven creation
Built-By: fdemelojWho created it
Build-Jdk: 11.0.14JDK that built it
Implementation-Title: Spring Boot Traditional SampleImplementation vendor details
Implementation-Version: 1.2.3.RELEASEImplementation vendor details
Implementation-Vendor-Id: org.springframework.bootImplementation vendor details
Implementation-Vendor: Pivotal Software, IncImplementation vendor details
Main-Class: org.springframework.boot.loader.WarLauncherSpring boot will be the main class
Start-Class: sample.traditional.SampleTraditionalApplicationSpring boot for app class
Spring-Boot-Version: 1.2.3.RELEASESpring boot example
DependenciesDeclare dependencies

For other properties that can be set on the manifest file, see Content from docs.oracle.com is not included.Java SE 8 Technotes Guides.

INDEX.LIST

There is another file: INDEX.LIST, this plays a role when classloader loads the jar file, it will reads the INDEX.LIST file and uses it to construct a hash table of mappings from file and package names to lists of jar file names. In order to find a class or a resource, the class loader queries the hashtable to find the proper jar file and then downloads if it is necessary.

$ tree
.
├── AClass.class
└── META-INF
    ├── INDEX.LIST <------
    ├── MANIFEST.MF <-----
    └── maven
        └── something

Diagnostic Steps

  1. Use the verbose option: v example: jar cvfm to see what is being added:
added manifest <-------- added manifest
adding: StandaloneClient.class(in = 1923) (out= 1078)(deflated 43%)
adding: EjbPrint.jar(in = 2595) (out= 1988)(deflated 23%)
adding: jsse.jar(in = 1917344) (out= 634716)(deflated 66%)
adding: jboss-client.jar(in = 19841869) (out= 17870289)(deflated 9%)
adding: wildfly-config.xml(in = 1766) (out= 792)(deflated 55%)
  1. Example packaging a manifest file (custom one wrote beforehand): $ jar cvfm myProj.jar manifest.txt *.*
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