Research On Key Technology Of Hard Java Real-Time Embedded Platform

With the rapid development of embedded and real-time computing, the development model of embedded real-time systems is undergoing rapid change. Compared with the traditional development model of assembly language or C/C++, Java has its own advantages of portability, high development efficiency, low cost of development and maintenance, etc. It also provides a higher layer of abstraction level, a higher level of data modeling, and a powerful library support. Java’s features of cross-platform, object-oriented, reliability, concurrent language supporting, strict type checking, robust and security make it own the basis of being the development language of embedded real-time systems. However, the standard Java is not designed for real-time application, so it can not fully meet the requirements of real-time system development. In light of this, some specifications involving the Real-Time Specifications for Java (RTSJ) and Safety Critical Java (SCJ) Specifications are published to make a series of improvement. Now, real-time Java has already owned the qualifications as a language for the development of embedded real-time systems, and a series of successful applications have arisen. In the aspect of real-time Java’s execution, the software engine execution modes have their own disadvantages. The interpreting mode is of low running speed and execution efficiency, and Just-In-Time technology requires relatively large system resources. Comparatively, a kind of hard Java execution engine mode based on Java processor, which can directly execute JVM bytecodes instructions set, greatly improve execution efficiency with lower resource occupancy, and well support real-time applications, may be one of the most effective execution engine mode currently for embedded real-time Java. The innovative achievements can be summoned as follows:Firstly, a non-heap memory model for hard Java real-time embedded platform which is runtime predictable is proposed. It eliminates the real-time influence on system introduced by runtime safety access rules checking, and remains the support for sharing and nesting non-heap memory without changing the Java syntax and programming mode.Secondly, a set of single parent rule and assignment rule check algorithms based on static analysis is proposed. This set of algorithms can complete rules checking staticly before the system is running without affecting the runtime system, so it avoids the overhead and realtime influence of the dynamic analysis and check.Thirdly, a kind of improved generational garbage collector for hard Java real-time embedded platform is designed. According to the target environment characteristics, this collector provides the collection strategy suitable for memory mangement of the environment, which improves collection efficiency, and reduces collection costs. It also avoids the frequent task suspension introduced by minor collection, and avoids object moving and memory fragments of major collection effectively. An object reference model applied to hard Java real-time embedded platform is put forward. This model provides effective support for object-tracking, heap space scanning, synchronization and so on.Fourthly, a predictable method invocation mode with high efficiency for hard Java real-time embedded platform is designed. This mode can ensure the runtime predictability of the method invocation, improve the execution efficiency of the method invocation, and reduce the execution clock cycles.