Java платформасында Ruby тілінің іске асырылуы: JRuby

Java implementation of Ruby

JRuby is an implementation of the Ruby programming language atop the Java Virtual Machine, written largely in Java. It is free software released under a three way EPL/GPL/LGPL license. JRuby is tightly integrated with Java to allow the embedding of the interpreter into any Java application with full two way access between the Java and the Ruby code (similar to Jython for the Python language). JRuby's lead developers are Charles Oliver Nutter and Thomas Enebo, with many current and past contributors including Ola Bini and Nick Sieger. In September 2006, Sun Microsystems hired Enebo and Nutter to work on JRuby full time. In June 2007, ThoughtWorks hired Ola Bini to work on Ruby and JRuby. In July 2009, the JRuby developers left Sun to continue JRuby development at Engine Yard. In May 2012, Nutter and Enebo left Engine Yard to work on JRuby at Red Hat.

JRuby was originally created by Jan Arne Petersen, in 2001. At that time and for several years following, the code was a direct port of the Ruby 1.6 C code. With the release of Ruby 1.8.6, an effort began to update JRuby to 1.8.6 features and semantics. Since 2001, several contributors have assisted the project, leading to the current (2012) core team of around six members. JRuby 1.1 added Just in time compilation and Ahead of time compilation modes to JRuby and was already faster in most cases than the then current Ruby 1.8.7 reference implementation. JRuby packages are available for most platforms; Fedora 9 was among the first to include it as a standard package at JRuby 1.1.1. In July 2009, the core JRuby developers at Sun Microsystems, Charles Oliver Nutter, Thomas Enebo and Nick Sieger, joined Engine Yard to continue JRuby development. In May 2012, Nutter and Enebo left Engine Yard to work on JRuby at Red Hat.

JRuby has been able to run the Ruby on Rails web framework since version 0.9 (May 2006), with the ability to execute RubyGems and WEBrick. Since the hiring of the two lead developers by Sun, Rails compatibility and speed have improved greatly. JRuby version 1.0 successfully passed nearly all of Rails's own test cases. Since then, developers have begun to use JRuby for Rails applications in production environments.

On February 27, 2008, Sun Microsystems and the University of Tokyo announced a joint research project to implement a virtual machine capable of executing more than one Ruby or JRuby application on one interpreter.

Since early 2006, the current JRuby core team has endeavored to move JRuby beyond being a simple C port, to support better performance and to aid eventual compilation to Java bytecode. To support this end, the team set an ambitious goal: to be able to run Ruby on Rails unmodified using JRuby. In the process of achieving this goal, the JRuby test suite expanded to such extent that the team gained confidence in the "correctness" of JRuby. As a result, toward the end of 2006 and in the beginning of 2007, they began to commit much more complicated redesigns and refactorings of JRuby's core subsystems. JRuby is designed to work as a mixed mode virtual machine for Ruby, where code can be either interpreted directly, just in time compiled at runtime to Java bytecode, or ahead of time compiled to Java bytecode before execution. Until October 2007, only the interpreted mode supported all Ruby's constructs, but a full AOT/JIT compiler is available since version 1.1. The compiler design allows for interpreted and compiled code to run side by side, as well as decompilation to reoptimize and outputting generated bytecode as Java class files.

JRuby has built in support for Rails, RSpec, Rake, and RubyGems. It embeds an FFI subsystem to allow the use of C libraries bundled as gems. It also allows launching the Interactive Ruby Shell (irb) as Ruby MRI does. The Netbeans Ruby Pack, available in NetBeans 6, allows IDE development with Ruby and JRuby, as well as Ruby on Rails for the two implementations of Ruby. It is no longer included in NetBeans 7.0 and later.

JRuby is similar to the standard Ruby interpreter except written in Java. JRuby features some of the same concepts, including object oriented programming, and dynamic typing as Ruby. The key difference is that JRuby is tightly integrated with Java, and can be called directly from Java programs. Java has significant footing in the development of web applications.

According to some benchmarks, JRuby is faster than alternatives. Since implementations vary in how much code is loaded before execution, different methods of measuring speed can lead to biased interpretations of performance advantages. The time it takes for a Java Virtual Machine itself to load is often excluded from execution times when calculating benchmarks. JRuby has the significant architectural advantage to be able to leverage JVM threads without being constrained by a global interpreter lock (similarly to Rubinius), therefore achieving full parallelism within a process, which Ruby MRI cannot achieve despite leveraging OS threads. In a real Mongrel web server application tested in 2007, JRuby performance is better than Ruby MRI 1.8, after the Java Virtual Machine had been instantiated. In a 2007 benchmark of Ruby implementations, JRuby was faster than Ruby MRI 1.8 in some tests, but YARV outperformed both of them. As of April 2014, in The Computer Language Benchmarks Game, JRuby 1.7.4 typically has the same performance as Ruby MRI 2.1.0, but uses more memory.