Apache Harmony

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Apache Harmony
Developer Apache Software Foundation
Latest release 5.0 M4 / December 19, 2007
OS Cross-platform
Genre Java SE 5
License Apache 2.0 license
Website http://harmony.apache.org/

Apache Harmony is an open source / free Java implementation, starting with Java SE 5.0. It will be licensed under the Apache License, Version 2. It was announced in early May 2005 and on October 25th 2006, the Board of Directors voted to make Apache Harmony a top-level project.

Contents

[edit] History

[edit] Initiation

The Harmony project was initially conceived as an effort to unite all developers of the Free Java implementations. Many developers expected that it would be the project above the GNU, Apache and other communities. GNU developers were invited into and participated during the initial, preparatory planning. Later it was decided not to use the code from GNU Classpath, and that Harmony would use an incompatible license; therefore blocking the sharing of code between Harmony and existing free Java projects. Apache developers would then write the needed classes from scratch and expect necessary large code donations from software companies.

[edit] Reasons for rewriting from scratch

The main reason for disagreements between the GNU Classpath and Apache projects is due to differences between the General Public License (GNU Classpath's license also contains the linking exception) and Apache License. These disagreements are inspired by various organizations and individuals[1] that prefer the Apache License, which allows for closed source derived works. GNU Classpath can also be linked[2] with proprietary code, but it is legally difficult to make a closed source derivative of GNU Classpath itself. However, many free software developers think that the licenses and philosophy of these communities are not different enough to split the efforts, and the inability to find compromises is frequently estimated negatively. The occasionally appearing suggestion to view these projects as opposing forces does not find wide support. Enthusiasts of the free software tend to break the discussion with the simple words that "more free software is not a problem".[3]

[edit] Difficulties to obtain a TCK license from Sun

The Apache Software Foundation sent the following letter to Sun Microsystems CEO, Jonathan Schwartz, on April 10, 2007, regarding their inability to acquire an acceptable license for the Java SE 5 Technology Compatibility Kit (TCK), a test kit needed by the project to demonstrate compatibility with the Java SE 5 specification, as required by the Sun specification license for Java SE 5.[4] What makes the license unacceptable for ASF is the fact that it impose rights restrictions through limits on the "field of use" available to users of Harmony, not compliant with the Java Community Process rules.[5]

Sun answered on a company blog [2][3] that it intended to create an open source implementation of the Java platform under GPL, including the TCK, but that their current priority was to make the Java Platform accessible to the GNU/Linux community under GPL as quickly as possible.

This answer triggered some reactions, either criticizing Sun for not responding in a sufficient open manner to an open letter [4], or rather Apache Software Foundation; some think that ASF acted unwisely to aggressively demand something they could have obtained with more diplomacy from Sun, especially considering the timescale of the opening class library [5] [6] .

[edit] Development team

Apache Harmony started from being mostly developed by several companies, receiving large code contributions at once. However, the general discussions on the mailing lists were always opened for everyone, and later the Apache Software foundation mentors put a lot of effort[6] to bring the development process more in line with the Apache way,[7] and it seems that their efforts were highly successful. In November 1, 2006, the current team of committers consisted of 16 developers, 12 of them from IBM and Intel.[8]

[edit] Recent development status

Apache Harmony has been accepted among the official Apache projects on 29th October 2006.

[edit] Library Coverage

The expected donations from software companies were actually received. The Apache Harmony now contains the working code, including the Swing, AWT and Java 2D code which were contributed by Intel.

The part of the implemented classes is still smaller than in GNU Classpath (97.7% in the trunk versus almost 100% as of July 2007[9]), despite some non-trivial applications were shown being running in 2006 JavaOne international conference.

Also Harmony's test suite is less extensive than GNU Classpath's for now (20000 tests [7] versus 50000 [8] as of October 2006).

The progress of the Apache Harmony project can be tracked against J2SE 1.4[10] and Java SE 5.0.[11] Also, there is a branch for Harmony v6.0 in development for java SE 6.0[9].

[edit] Documentation

Harmony is currently less documented than the alternative free java implementations. For instance, in GNU Classpath every method of the central CORBA class (ORB) has the explaining comment both in the standard abstract API class [10] and implementation [11]. In the Yoko project, used by Harmony [12], the majority of methods both in the standard declaration [13] and implementing class [14] were not documented (at the end of October, 2006). Also, GNU Classpath supported both older and current CORBA features (same as Sun's implementation). Harmony, differently, left the central method of the older standard (ORB.connect(Object)) fully unimplemented.

[edit] Tools

A complete implementation of the Java platform also requires a compiler that translates Java source code into bytecodes, a program that manages JAR files, a debugger, and an applet viewer and web browser plugin, to name a few. Harmony currently only has the compiler [15].

[edit] Virtual machine support

Harmony currently has four virtual machine implementations, all of which were donations by external groups:

  • JC Harmony Edition VM, "JCHEVM," based on the JCVM's interpreter, contributed by the author, Archie Cobbs.
  • BootJVM, a simple bootstrapping virtual machine, contributed by Daniel Lydick.
  • SableVM, an advanced, portable interpreter, contributed by authors from the Sable Research Group; and the Dynamic Runtime Layer Virtual Machine.
  • DRLVM, a just-in-time compiler contributed by Intel.
  • BEA announced the availability of an evaluation version of JRockit VM running Apache Harmony Class Library.[12]

In the end of November, 2006, the language support provided by these virtual machine was still incomplete, and the build instructions recommended to use IBM's proprietary J9 instead to run the class library test suite [16]. However, this is not necessary anymore (as of July 2007).

The DRLVM virtual machine is currently (as of July, 2006) under heavy development, so a fast improvement of its features can be expected.

[edit] Applications status

Since its conception, Harmony has steadily grown in its ability to execute non-trivial Java applications (see here). As of July 2007, supported applications include:

However, Harmony's incomplete library prevents it from launching some other applications:

[edit] See also

Free Software Portal

[edit] References

  1. ^ Mark Wielaard (2006-05-24). Toward a free Java. LWN.net.
  2. ^ GNU Classpath License.
  3. ^ Dalibor Topic (2006-06-01). Harmony, JavaONE 2007 and other thoughts.
  4. ^ Open Letter to Sun Microsystems
  5. ^ According to ASF, 1) a specification lead cannot impose any contractual condition or covenant that would limit or restrict the right of any licensee to create or distribute such Independent Implementations (section 5.C.III), and 2) a specification lead must license all necessary IP royalty-free to any compatible implementation of a specification (section 5.B).
  6. ^ Leo Simons (2006-07-24). "We would like all the development to happen right here".
  7. ^ The Apache Way.
  8. ^ List of Apache Harmony Committers.
  9. ^ that a class is implemented does not imply that this class behaves as requested in the RI specification. For example, some implemented methods can still do nothing at all (this is also true for GNU Classpath)
  10. ^ Apache Harmony Library Coverage against J2SE 1.4
  11. ^ Apache Harmony Library Coverage against Java SE 5.0
  12. ^ BEA JRockit VM under a binary, evaluation-only license[1].

[edit] External links

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Java Virtual Machines
Sun HotSpot · Apache Harmony · BEA JRockit · GCJ · Squawk · IKVM · JX · Kaffe · SableVM · CACAO · JikesRVM · JNode · JamVM · IcedTea · Microsoft JVM · more…
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Apache Software Foundation
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Other projectsJakarta Project · Apache Lucene · Apache XML · Apache Incubator
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License: Apache License · Website: http://apache.org/
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