JDK-8305603 : Release Note: Remove the JAR Index Feature
  • Type: Sub-task
  • Component: core-libs
  • Sub-Component: java.util.jar
  • Affected Version: 21
  • Priority: P4
  • Status: Resolved
  • Resolution: Delivered
  • Submitted: 2023-04-04
  • Updated: 2023-07-28
  • Resolved: 2023-04-13
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JDK 21
21Resolved
Description
The "JAR Index" feature has been dropped from the JAR file specification. JAR Index was a legacy optimization in early JDK releases to allow downloading of JAR files to be postponed when loading applets or other classes over the network. The feature has been disabled since JDK 18, meaning the `META-INF/INDEX.LIST` entry in a JAR file is ignored at run-time.

The system property `jdk.net.URLClassPath.enableJarIndex`, introduced in JDK 18 to re-enable the feature, has been removed. Setting this property no longer has any effect. 

As part of the change, the `jar` tool will now output a warning if the `-i` or `--generate-index` options are used.
Comments
Thanks Alan for your thoughtful editing. It reads a lot cleaner now.
14-04-2023
I edited this RN to expand the first paragraph and remove the warning from the 3rd paragraph. I think it's good now.
14-04-2023
We should probably update the RN to indicate that the system property jdk.net.URLClassPath.enableJarIndex has been removed as well as indicate the warning messages that users will receive. I would suggest formatting the RN similar to: https://bugs.openjdk.org/browse/JDK-8278458 for each section
05-04-2023