Real-time Java
| Industry | Software, Real-time computing |
|---|---|
| Founded | 2001 |
| Founder | Kelvin Nilsen |
| Products | Real-Time Specification for Java (RTSJ), Timesys reference version, IBM WebSphere Real Time, Sun Microsystems Java SE Real-Time Systems, PTC Perc, JamaicaVM |
Real-time Java encompasses a set of technologies that allow developers to create applications capable of fulfilling the stringent requirements of real-time systems using the Java language.
The widespread use of Java in multiple sectors is attributed to its sophisticated memory management, inherent support for multithreading and concurrency, robust type safety, and ease of use. To address real-time constraints, Java has been enhanced with features such as:
- A rigorous priority-driven thread scheduling framework,
- Locking constructs designed to mitigate priority inversion through mechanisms like priority inheritance and the priority ceiling protocol,
- Event handling tailored for improved real-time responsiveness.
The concept of real-time Java was first proposed by Kelvin Nilsen from Iowa State University in an open standard format, followed by an in-depth description published in the Communications of the ACM. The favorable reception from industry stakeholders prompted the National Institute of Standards and Technology (NIST) to organize standardization discussions, which culminated in agreed-upon requirements after NIST was informed that Sun Microsystems, the proprietor of Java, would oversee forthcoming standards.
Subsequently, with the establishment of the Java Community, JSR001 became the inaugural specification outlining the Real-time specification for Java (RTSJ). Multiple implementations were developed, including Timesys’ reference version, IBM’s WebSphere Real Time, Sun Microsystems’ Java SE Real-Time Systems, PTC Perc from PTC, Inc., and aicas’ JamaicaVM.
The RTSJ defines a baseline threading model while permitting alternative models within the virtual machine. It introduces specialized memory regions exempt from garbage collection through region-based memory management, and supports threads that are not preemptible. The most recent RTSJ 2.0 update incorporates features such as direct hardware access and deterministic garbage collection.
Real-Time Specification for Java
The Real-Time Specification for Java (RTSJ) establishes interfaces and behavioral modifications to facilitate real-time programming on the Java platform. RTSJ 1.0 was formalized as JSR 1 via the Java Community Process and officially approved in November 2001. RTSJ 2.0, currently under development as JSR 282, offers additional improvements; a draft version is accessible through the JCP. Companies like Aicas provide implementations that comply with RTSJ standards and offer related support.
See also
- Javolution – a Java library compliant with RTSJ
External links
- Issues in the Design and Implementation of Real-Time Java
- Adding Real-Time Capabilities to Java
- Requirements for Real-Time Extensions for the Java Platform
- Real-Time Specification for Java 2.0 (RTSJ 2.0)
- JSR-282
- Real-Time Specification for Java (RTSJ)
- JSR-1
- IBM WebSphere Real Time – fully compliant RTSJ SE VM
- JamaicaVM – RTSJ SE implementation featuring deterministic garbage collection
- PTC Perc – real-time VM based on Java SE incorporating patented deterministic garbage collection technology
- Sun Java SE Real-Time System
- Timesys RTSJ implementation and testing toolkit
- jRate (Java Real-Time Extension) – open-source extension adding RTSJ capabilities to GNU GCJ
- LJRT Lund Java-based Real-Time open source