Apache Harmony

Apache Harmony

Developer(s)	Apache Software Foundation
Stable release	5.0M15 6.0M3 / September 15, 2010 (2010-09-15)
Development status	Discontinued
Written in	C++, Java
Operating system	Windows, Linux
Type	Java Virtual Machine, Java Library
License	Apache License 2.0
Website	harmony.apache.org

Apache Harmony is a retired open source, free Java implementation, developed by the Apache Software Foundation. It was announced in early May 2005 and on October 25, 2006, the Board of Directors voted to make Apache Harmony a top-level project. The Harmony project achieved (as of February 2011) 99% completeness for J2SE 5.0, and 97% for Java SE 6. The Android operating system is a major user of Harmony, but it's next version uses OpenJDK libraries gaining, e.g. some features of Java 8 (that is, excluding its JVM).

On October 29, 2011 a vote was started by the project lead Tim Ellison whether to retire the project. The outcome was 20 to 2 in favor, and the project was retired on November 16, 2011.

History

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.

Incompatibility with GNU Classpath

Despite the impression given by the preparatory planning, it was decided not to use the code from GNU Classpath, and that Harmony would use an incompatible license; therefore blocking the collaboration 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. Various misunderstandings at the start of the project, and the fact that major companies like IBM proposed to give large amount of existing code, created some confusion in the free Java community about the real objectives of the project.

One major point of incompatibility between the GNU Classpath and Apache Harmony projects was their incompatible licenses: Classpath's GNU General Public License with the linking exception versus Harmony's Apache License.

Difficulties to obtain a TCK license from Sun

See also: Technology Compatibility Kit

On April 10, 2007, the Apache Software Foundation sent an open letter to Sun Microsystems CEO, Jonathan Schwartz 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 needed by the Sun specification license for Java SE 5. What makes the license unacceptable for ASF is the fact that it imposes rights restrictions through limits on the "field of use" available to users of Harmony, not compliant with the Java Community Process rules.

Sun answered on a company blog 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 sufficiently open manner" to an open letter, 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.

Since Sun's release of OpenJDK, Sun has released a specific license to allow to run the TCK in the OpenJDK context for any GPL implementation deriving substantially from OpenJDK.

On December 9, 2010, the Apache Software Foundation resigned from the Java Community Process Executive Committee, in protest over the difficulty in obtaining a license acceptable to Apache for use with the Harmony project.

Use in Android SDK

Dalvik, the virtual machine that was used in Google's Android platform up to version 4.4 (and Android Runtime (ART), that followed), uses a subset of Harmony for the core of its Class Library. However, Dalvik does not align to Java SE nor Java ME Class Library profiles (for example J2ME classes, AWT and Swing are not supported).

In December 2015, Google announced that the next version of Android would use OpenJDK libraries instead.

Disengagement from IBM

On October 11, 2010, IBM, by far the biggest participant in the project, decided to join Oracle on the OpenJDK project, effectively shifting its efforts from Harmony to the Oracle reference implementation. 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".

On March 2011, IBM's Tim Ellison announced that he resigned as Project Management Chair for Harmony, a move which brought questions about the future of the project. Since the beginning of 2011, there has been almost no more development on the project, nor discussions on the mailing list.

End of the project

On October 29, 2011, a poll was started on the harmony-dev mailing list by the project lead Tim Ellison whether to retire the project. The outcome on November 3, was 20 to 2 in favor of retirement. On November 16, 2011, the Apache Software Foundation board of directors passed a motion to terminate the project. One director, Larry Rosen, cast a "no" vote, based on the timing rather than the merits of the proposal; it was otherwise unanimous. The project was retired on November 16, 2011.

Development team

At the start, Apache Harmony received some large code contributions from several companies. Development discussions have taken place on open mailing lists. Later, the Apache Software foundation mentors put a lot of effort into bringing the development process more in line with "the Apache way," and it seemed that their efforts were successful.

Last development status

Apache Harmony was accepted among the official Apache projects on October 29, 2006.

Architecture

The Dynamic Runtime Layer virtual machine consists of the following components:

1. The VM core: with its subcomponents concentrates most of the JVM control functions.
2. The porting layer: hides platform-specific details from other VM components behind a single interface and is based on the Apache Portable Runtime layer.
3. The garbage collector: allocates Java objects in the heap memory and reclaims unreachable objects using various algorithms
4. Execution Manager: selects the execution engine for compiling a method, handles profiles and the dynamic recompilation logic.
5. Class Library: is a Java standard library.
6. The thread manager that handle operating system threading
7. The execution engine: consists of the following:
   1. The just-in-time compiler for compilation and execution of method code.
   2. The interpreter for easier debugging.

Support platform and operating system

The project provided a portable implementation that ease development on many platforms and operating systems. The main focus was on Windows and Linux operating systems on x86 and x86-64 architectures.

	Windows 2000	Windows XP, Server 2003, Vista	Linux RHEL, SLES, Debian, Gentoo, Fedora	FreeBSD	AIX	Mac OS X
IA-32 (Pentium III or better)	No	Yes	Yes	No	N/A	N/A
x86-64 (Intel 64, AMD64)	N/A	Yes	Yes	N/A	N/A	N/A
Itanium (IA64, IPF)	N/A	No	Yes	N/A	N/A	N/A
PowerPC 32-bit	N/A	N/A	No	N/A	N/A	N/A
PowerPC 64-bit	N/A	N/A	No	N/A	No	N/A
zSeries 31-bit	N/A	N/A	No	N/A	N/A	N/A

Class 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 Harmony project currently achieve (as of February 2011) 99% completeness for JDK 5.0, and 97% for Java SE 6.

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

Apache Harmony developers integrate several existing, field-tested open-source projects to meet their goal (not reinventing the wheel). Many of these projects are mature and well known and other parts of the library needed to be written from scratch.

This is a list of existing open source components that are used in the Apache Harmony project; some of them were in use before the project started.

Component	Description
ICU	Mature C/C++ and Java libraries for Unicode support and software internationalization and globalization
Apache Xalan	XSLT stylesheet processor for Java, C++ which implements XPath language
Apache Xerces	XML parser library for Java, C++, Perl
Apache Portable Runtime	Cross-platform abstraction library, provides platform independence
Apache CXF	Robust, high performance Web services framework work over protocols such as SOAP, XML/HTTP, RESTful HTTP, CORBA
BCEL	Libraries to decompose, modify, and recompose binary Java classes, i.e., bytecode
MX4J	Java Management Extensions (JMX) tools to manage and monitor applications, system objects, devices and service-oriented networks
VM Magic	Set of extensions to Java language to facilitate systems programming in Java by adding direct memory operations, etc.
Bouncy Castle	Libraries collection of lightweight cryptography for Java and C#
ANTLR	Language tool, provides a framework to construct recognizers, interpreters, compilers, and translators from grammatical descriptions containing actions in many target languages

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 and implementation. In the Yoko project, used by Harmony, most methods both in the standard declaration and implementing class were undocumented 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.

Tools

A complete implementation of the Java platform also needs 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 has the compiler, appletviewer, jarsigner, javah, javap, keytool, policytool, and unpack200 [1].

Virtual machine support

Harmony currently has seven virtual machine implementations that run Harmony Class Library, 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.
• JikesRVM, an open-source meta-circular JVM that use the Apache Harmony Class Library.
• Ja.NET SE, an open source project providing a Java 5 JDK (class libraries, tools, etc.) that run on the .NET Framework CLR. Ja.NET SE is based on the Apache Harmony Class Libraries.

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. However, this is not necessary anymore (as of July 2007).

As for the rest of the project, DRLVM virtual machine development has now stalled (as of May 2011).

Application status

Since its conception, Harmony grew in its ability to execute non-trivial Java applications. As of July 2007, supported applications include:

• Eclipse: 99.3% of the 36000 reference implementation (RI) test pass on Harmony's DRLVM + class library.
• Apache Tomcat: 100% of the RI tests pass.
• JUnit: 100% of the RI tests pass.
• Apache Ant: 97% of the RI tests pass.
• Other applications pass with a high success rate, such as Apache Derby, Apache Axis, Log4j, Apache Velocity, Apache Cocoon, jEdit, and Apache Commons.

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

• ArgoUML: because it needs a Java applet implementation, which was still unavailable in Harmony.
• Apache Geronimo runs on Apache Harmony with some issues and workarounds.
• Vuze, formerly Azureus, because of unimplemented security classes.

See also

• GNU Classpath
• List of Java virtual machines
• Free Java implementations
• Java Class Library
• OpenJDK
• IcedTea

External links

• Apache Harmony FAQ
• Apache Harmony source code repository
• JavaOne 2006 Online Harmony Session
• JavaOne 2007 Online Harmony Session
• Apache Harmony by Geir Magnusson Jr at JavaPolis 2006
• The Java open source debate - a good summary of the debate
• What is the Future of Apache Harmony?
• Apache Harmony loses project manager