What is OpenJDK

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http://en.wikipedia.org/wiki/OpenJDK

 

OpenJDK (aka Open Java Development Kit ) is a free and open source implementation of the Java programming language .^{[clarification needed ]} It is the result of an effort Sun Microsystems began in 2006. The implementation is licensed under the GNU General Public License (GPL) with a linking exception , which exempts components of the Java class library from the GPL licensing terms.

 

History

Sun's promise and initial release

Sun announced in JavaOne 2006 that Java would become open-source software, and on October 25, 2006, at the Oracle OpenWorld conference, Jonathan Schwartz said that the company intended to announce the open-sourcing of the core Java Platform within 30 to 60 days.

Sun released the Java HotSpot virtual machine and compiler as free software under the GNU General Public License on November 13, 2006, with a promise that the rest of the JDK (which includes the Java Runtime Environment ) would be placed under the GPL by March 2007, "except for a few components that Sun does not have the right to publish in source form under the GPL". According to computer scientist and free-software advocate Richard Stallman , this would end the "Java trap", the vendor lock-in that he argues applied to Java and programs written in Java. Software entrepreneur Mark Shuttleworth called the initial press announcement "A real milestone for the free software community ". ^{[not in citation given ]}

Release of the class library

Following their promise to release a Java Development Kit (JDK) based almost completely on free and open source code in the first half of 2007 , Sun released the complete source code of the Java Class Library under the GPL on May 8, 2007, except for some limited parts that some third parties licensed to Sun that rejected the terms of the GPL. Included in the list of encumbered parts were several major components of the Java graphical user interface (GUI). Sun stated that it planned to replace the remaining proprietary components with alternative implementations and to make the class library completely free.

Community improvements

On November 5, 2007, Red Hat announced an agreement with Sun, signing Sun's broad contributor agreement (which covers participation in all Sun-led free and open source software projects by all Red Hat engineers) and Sun's OpenJDK Community TCK License Agreement (which gives the company access to the test suite that determines whether a project based on openJDK complies with the Java SE 6 specification).

Also on November 2007, the Porters Group was created on OpenJDK to aid in efforts to port OpenJDK to different processor architectures and operating systems . The BSD porting projects , led by Kurt Miller and Greg Lewis and the Mac OS X porting project (based on the BSD one) SoyLatte led by Landon Fuller  have expressed interest in joining OpenJDK via the Porters Group and as of January 2008 are part of the mailing list discussions. Another project pending formalization on the Porters Group is the Haiku Java Team, led by Bryan Varner.

On December 2007, Sun moved the revision control of OpenJDK from TeamWare to Mercurial , as part of the process of releasing it to open source communities.

OpenJDK has comparatively strict procedures of accepting code contributions: every proposed contribution must be reviewed by two of Sun's engineers and the contributor must have signed the Sun/Oracle Contributor Agreement.(SCA/OCA ) Preferably, there should also be a JTreg test demonstrating that the bug has been fixed. Initially, the external patch submission process was and commits to the codebase were only made by Sun engineers, until September 2008 . The process has improved and, as of 2010^[update] , simple patches and backports from OpenJDK7 to OpenJDK6 can take place within hours rather than days.

On 2010-10-11, IBM and Oracle announced that both companies will collaborate to further develop OpenJDK.

On 2010-11-12, Apple and Oracle announced the OpenJDK project for Mac OS X .

Status

Supported JDK versions

OpenJDK was initially based only on the JDK 7.0 version of the Java platform.

Since February 15, 2008, there are two separate OpenJDK projects:

• The main OpenJDK project, which is based on the JDK 7.0 version of the Java platform,
• The JDK 6 project, which provides an Open-source version of Java 6.0 .

Compiler and Virtual Machine

Sun's Java compiler, javac , and HotSpot (the virtual machine ), are now under a GPL license.

Class library

See also: Java Class Library

As of the first May 2007 release, 4% of the OpenJDK class library remained proprietary . By the appearance of OpenJDK 6 in May 2008, less than 1% (the SNMP implementation , which is not part of the Java specification) remained , making it possible to build OpenJDK without any binary plugs The binary plug requirement was later dropped from OpenJDK7 as part of b53 in April 2009 .

This was made possible, over the course of the first year, by the work of Sun Microsystems and the OpenJDK community. Each encumberance was either released as free and open source software or replaced with an alternative:

• All the audio engine code, including the software synthesizer , has been released as open source. The proprietary software synthesizer has been replaced by a new synthesizer developed specifically for OpenJDK called Gervill   ,
• All cryptography classes used in the class library have been released as open source ,
• The code that scales and rasterizes fonts has been replaced by FreeType
• The native color management system has been replaced by LittleCMS . There is a pluggable layer in the JDK, so that the proprietary version can use the old color management system and OpenJDK can use LittleCMS.
• The anti-aliasing graphics rasterizer code has been replaced by the open source Pisces renderer used in the phoneME project. This code is fully functional, but still needs some performance enhancements

Sun has made continued promises about releasing their plugin^{[clarification needed ]} and Web Start implementation as part of OpenJDK, but have so far failed to deliver . The only currently available free plugin and Web Start implementation is that provided by IcedTea.

IcedTea and Inclusion in Software Distributions

Main article: IcedTea

To be able to bundle OpenJDK in Fedora and other free Linux distributions, OpenJDK needed to be buildable using only free software components. Due to the encumbered components in the class library and implicit assumptions within the build system that the JDK being used to build OpenJDK was a Sun JDK , this was not possible. In order to achieve this goal, a project called IcedTea was started by Red Hat in June 2007. It began life as an OpenJDK/GNU Classpath hybrid that could be used to bootstrap OpenJDK, replacing the encumbrances with code from GNU Classpath.

On November 5, 2007, Red Hat signed both the Sun Contributor Agreement and the OpenJDK Community TCK License. One of the first benefits of this agreement is tighter alignment with the IcedTea project, which brings together Fedora , the Linux distribution, and JBoss , the application server, technologies in a Linux environment. IcedTea is providing free software alternatives for the few remaining proprietary sections in the OpenJDK project.

In May 2008, the Fedora 9 and Ubuntu 8.04 distributions included IcedTea 6, based completely on free and open source code. Fedora 9 was the first version to ship with IcedTea6, based on the OpenJDK6 sources from Sun rather than OpenJDK7. It was also the first to use OpenJDK for the package name (via the OpenJDK trademark agreement ) instead of IcedTea. Ubuntu also first packaged IcedTea7 before later moving to IcedTea6. Packages for IcedTea6 were also created for Debian and included in lenny . On July 12, 2008, Debian accepted OpenJDK-6 in unstabl , and it is now in stable . OpenJDK is also available on openSUSE , Red Hat Enterprise Linux and RHEL derivatives such as CentOS .

In June 2008, Red Hat announced that the packaged binaries for OpenJDK on Fedora 9 , built using IcedTea 6, had passed the Technology Compatibility Kit tests and could claim to be a fully compatible Java 6 implementation. In July 2009, an IcedTea 6 binary build for Ubuntu 9.04 passed all of the compatibility tests in the Java SE 6 JCK .

Since August 2008, OpenJDK 7 is runnable on Mac OS X and other BSD distributions.

Collaboration with IBM

On October 11, 2010, IBM , by far the biggest participant in the Apache Harmony project, decided to join Oracle on the OpenJDK project, effectively shifting its efforts from Harmony to OpenJDK . Bob Sutor, IBM's head of Linux and open source, blogged that "IBM will be shifting its development effort from the Apache Project Harmony to OpenJDK". .

Java on Mac OS X

On November 12, 2010, just three weeks after deprecating its own Java runtime port , Apple and Oracle announced the OpenJDK project for Mac OS X. Apple will contribute most of the key components, tools and technology required for a Java SE 7 implementation on Mac OS X, including a 32-bit and 64-bit HotSpot-based Java virtual machine, class libraries, a networking stack and the foundation for a new graphical client .