Modules

TheModulesProject is inactive. The approach described here was supersededbyProject Jigsaw.

This page covers the implementation of the modularityspecifications defined by JSR 277 and JSR 294 as well as therelated work in the JDK. It is targeted for inclusion in JDK 7.

Introduction

Superpackages are a new language construct for informationhiding that is being defined by JSR 294, and it defines thelinguistic unit of modularity in the Java programming language. TheJava Module System defined by JSR 277 builds on top of that bydefining the deployment unit of modularity; it adds the versioningscheme, distribution format, repository and the comprehensiveruntime architecture for the deployment of module-basedapplications and libraries. In addition to the specificationsdefined by JSR 277 and JSR 294, other parts of the JDK will beupdated to take advantage of the new features, for example the Javalauncher program (bin/java), thejava.util.ResourceBundle API, the java.util.ServiceLoader API,etc.

The Modulesproject hosts the referenceimplementation of the new core functionality and serves as anumbrella for other related work items developed by other OpenJDKgroups.

Status

Early access source code is now available from theOpenJDK download site.Please read the notes below and check out thedocumentation.

Note that this is a live snapshot of the ongoing developmentproject before it is integrated into the main OpenJDK source tree.At this time, the code may not be as stable or complete as the restof OpenJDK. It is made available to allow all members of OpenJDKcommunity to collaborate in the development process and to allowfor early feedback from interested observers.

The implementation project tracks the specifications developedby JSR 277 and JSR 294. However, it may sometimes be out-of-syncwith those specifications. At times it may lag behind them orcertain features may not be implemented. At other times theimplementation may prototype features to explore their feasibilitybefore they are added to the specifications.

Features

Currently implemented:

• Implementation of the classes in java.module
• Module initialization and class loading
• LocalRepository and URLRepository core functionality
• Launching modules using thejava command
• Prototypejam packaging tool

Not yet implemented:

• See the daily bug list emails on themodules-dev list

Specifications

• JSR 277earlydraft (October 2006, new draft expected soon)

• JSR 277expertgroup observer mailing list.

• JSR 277 APIs. The source for thejava.modulepackage is available under the directorysrc/share/classes in theimplementationsources.

• JSR 294 superpackagestrawman

• JSR 294expertgroup mailing list and archive.

• JSR 294 reflective APIs. The sources for the classjava.lang.reflect.Superpackage as well as the proposedupdates tojava.lang.Class andjava.lang.ClassLoader are available under thedirectorysrc/share/classes in theimplementation sources. Also available are the updatesto thejavax.lang.model APIs that will be made by amaintenance revision ofJSR 269.

Source Code

• Source bundle available at theOpenJDK downloadsite.

Documentation

• Getting started with theModules project

• Sample modules

• Modules support in JDK tools

• Superpackage declarations

• Visibility policy

Community

• Mailing lists

  • modules-dev@openjdk:Technical discussion about the implementation of the modulesproject

  • modules-discuss@openjdk:General discussion of the modules project and how to usemodules

• Bloggers
  • StanleyHo
  • AlexBuckley
  • MandyChung
  • Dave Bristor