Research & Realization Of Exception Handling And Its Real-time Ability In JVM

Many of the advantages of Java, such as safe object references, the notion of concurrency as a first-class language construct, and its portability, have the potential to make embedded systems much safer and simpler to program. With the advantages mentioned above, Java is increasingly expected to become the leading programming language in embedded systems.Since Java virtual machine loads, analyze and link dynamically these needed classes when they are reference, these action influence system's real-time ability. And the GC running automatically leads to unprediction of task's running time. Java specification and JVM specification discuss generally in aspect of thread scheduling, it leads to different thread scheduling performance happened in different virtual machine.In aspect of Exception, to JVM, because of unreasonable design in Exception table, there are too much action (push and pop) unnecessary and it leads that the time of searching matched Exception fluctuates out of real-time range. To interrupted mechanism, current interrupted mechanism can not resolve all the problem they already have. These make JVM must have higher performance to fit our requirements.To improve the real-time performance specified in the Java Language Specification and the Java Virtual Machine Specification, Greg Bollella et al propose the Real-Time Specification for Java (RTSJ). It provides a guideline for the implementation of real-time Java platform.The main research content of this paper is how to improve the traditional Java virtual machine.Firstly, I analysis Exception handling mechanism of JVM thorough, and find out shortage of this mechanism. Then, propose a new lined struction to replace the Exception_table in JVM's stack. This replacement must make the time of searching matched Exception element appear lined change. I test this structure in different circumstances to prove it could improve the performance and real-time ability of JVM.Secondly, RTSJ put forward ATC to improve control and restrictions among threads. In order to simulate ATC in SableVM, propose a new method: open a memory area which each threads could access to store ATC Exception(AIE) thrown mightily by running threads. During this, there are specific circumstances might happen, I simulate some of them and prove this method could achieve ATC's performance in JVM.