Research Of Real-time Middleware Based On Java

Real-time middleware mainly follows real-time CORBA specification, and developed by using C++. There key reason that Java platform is not used to develop real-time middleware is: normal Java thread can not be scheduled executed according to priority. Experiments shows that same Java program have different operation results in different operating system. Thread scheduling is implementation-dependent and varies by platform. Java loses its characteristic of platform-independence. Predictability of real-time system can not be guaranteed. Java can construct real-time system by implementing RTSJ (Real-time Specification for Java) which can enhance openness of Java. However, to implement the RTSJ, support from operating system, Java runtime environment and Java develop kit are essential. It is not suitable for common Java platform to develop real-time system.This paper mainly research on the issue that the execution of thread is unpredictable while Java is used in soft-real-time middleware for network services. Aiming at the problem of Java thread can not be notified according to priority while multithreading access the critical resource, a component that can notify waiting thread based on priority is designed and implemented. The component can guarantee the high priority thread obtaining the critical resource firstly and reach the objective of improving Java real-time performance under common Java platform. The key design idea and implement approach is: creating new Java thread class in which priority being extended by equal proportional mapping mechanism; and then, creating thread agent that include notification priority information for each thread which sharing the critical resource; notification of the waiting thread being realized by the agent set class that only related to the critical resource according to priority in the agent set. Meanwhile, Solutions to the problems of synchronized data accessing and live-lock in developing Java real-time middleware are given by introducing scheduling algorithm of real-time system. Experiments show that threads in the waiting set always notify based on priority by using the component. It is conclude that the component can create Java thread that can be notified based on priority and its running can be predicted, meanwhile, the proposed priority equal proportional mapping mechanism solve the problem of original Java thread priority level being too small to schedule more thread according to priority effectively. By introducing dynamic priority algorithm from real-time system, the problem of live-lock meeting in middleware developing process can be solved effectively.