【摘要】：隨著嵌入式計算及實時計算的迅速發(fā)展,嵌入式實時開發(fā)模式正在經(jīng)歷快速變革,與傳統(tǒng)的采用匯編語言或者C/C++的開發(fā)模式相比,Java不僅在可移植性、高開發(fā)效率、低開發(fā)/維護(hù)成本等方面有自身的優(yōu)勢,而且能夠提供更高層次的抽象水平,可以滿足更高級別的數(shù)據(jù)建模需求,同時還具有強大的類庫支持。Java的跨平臺、面向?qū)ο�、可靠性、語言級的并發(fā)支持、嚴(yán)格的類型檢查、健壯、安全等特點,使其具備了作為嵌入式實時開發(fā)語言的基礎(chǔ),但是標(biāo)準(zhǔn)Java并非專門為實時應(yīng)用設(shè)計,尚不能夠完全滿足實時系統(tǒng)開發(fā)的要求,還需要有針對性地進(jìn)行Java的實時擴展和規(guī)范。隨著實時Java社區(qū)的努力,以及Java實時規(guī)范(RTSJ)和安全關(guān)鍵Java(SCJ)的推出,擴展后的實時Java具備了作為嵌入式實時開發(fā)語言的資格,而且得到了一系列成功的應(yīng)用。目前,針對實時Java及其支撐平臺的研究逐漸成為熱點,出現(xiàn)了一些支持實時Java的平臺和虛擬機,這些平臺和虛擬機大多以軟件的形式實現(xiàn)。對于資源受限的嵌入式實時系統(tǒng)而言,軟件Java平臺和虛擬機由于通常存在著運行速度慢、執(zhí)行效率低、資源開銷大等問題,在發(fā)揮Java的性能優(yōu)勢方面仍然面臨一定的困難。相對而言,采用Java處理器直接執(zhí)行字節(jié)碼,實現(xiàn)一種硬Java(hard Java)的引擎執(zhí)行模式,可以在提高運行效率的同時,大幅度降低功耗與資源占有率,尤其適合資源受限環(huán)境的嵌入式實時Java應(yīng)用。 本文設(shè)計并實現(xiàn)了一款能夠支持實時Java的用于資源受限環(huán)境的硬Java實時嵌入式平臺hJrep(hard Java real-time embedded platform),并對其中的關(guān)鍵技術(shù)進(jìn)行了深入研究和探討。hJrep以Java處理器為執(zhí)行引擎,以Java字節(jié)碼作為本地指令,實現(xiàn)了對字節(jié)碼的硬件直接執(zhí)行。本文的主要創(chuàng)新性工作包括： (1)為硬Java實時嵌入式平臺提出了一種運行時可預(yù)測的非堆內(nèi)存模型,該模型消除了運行時安全訪問檢查對系統(tǒng)實時性的影響,在不改變Java句法與編程模式的前提下,保留了對非堆內(nèi)存多線程共享及嵌套的支持。 (2)提出了一套基于靜態(tài)分析的單親規(guī)則檢查算法與賦值規(guī)則檢查算法,該套算法可以在系統(tǒng)運行前靜態(tài)完成規(guī)則檢查,不對運行時系統(tǒng)產(chǎn)生影響,避免了動態(tài)分析與檢查的運行時開銷和實時性影響。 (3)為硬Java實時嵌入式平臺設(shè)計了一種改進(jìn)的分代式垃圾收集器,該收集器針對目標(biāo)環(huán)境特征,提供了適用于目標(biāo)環(huán)境內(nèi)存管理的高效低開銷的回收策略,有效避免了頻繁的次級收集暫停,避免了成熟空間收集的對象移動開銷和內(nèi)存碎片問題。針對垃圾收集,設(shè)計了一種適用于硬Java實時嵌入式平臺的對象引用模型,該模型為對象追蹤、堆空間掃描、同步等提供了有效支持。 (4)為硬Java實時嵌入式平臺設(shè)計了一種高效的可預(yù)測的方法調(diào)用實現(xiàn)模式,保證了方法調(diào)用的運行時可預(yù)測,提高了方法調(diào)用的執(zhí)行效率,減少了方法調(diào)用的執(zhí)行周期。
[Abstract]:With the rapid development of embedded computing and real-time computing, the embedded real time development mode is undergoing rapid changes. Compared with the traditional use of assembly language or C/C++, Java has its own advantages not only in portability, high development efficiency, low development / maintenance cost, but also to provide a higher level of abstraction. At the same time, it can meet the higher level of data modeling requirements, and it also has strong class libraries to support.Java's cross platform, object oriented, reliability, language level concurrency support, strict type check, robustness, security and so on, so that it has the basis of embedded real time development language, but standard Java is not specially for real time. With the design, it is still not able to fully meet the requirements of real time system development. It also needs to carry out the real-time extension and specification of Java. With the efforts of the real-time Java community, and the introduction of the Java real-time specification (RTSJ) and the security key Java (SCJ), the extended real-time Java has the qualification as the embedded real-time development language. At present, the research on real-time Java and its support platform has become a hot spot. There are some platforms and virtual machines that support real-time Java. Most of these platforms and virtual machines are implemented in the form of software. For the embedded real-time system with limited resources, software Java platform and virtual machine are usually due to the common reason. There are many problems, such as slow running speed, low execution efficiency and high resource overhead, and still face certain difficulties in playing Java performance advantages. Relatively speaking, using Java processor to execute bytecode directly to implement a hard Java (hard Java) engine execution mode can greatly reduce power and capital while improving operation efficiency. Source occupancy is especially suitable for embedded real-time Java applications in resource constrained environments.
This paper designs and implements a hard Java real-time embedded platform hJrep (hard Java real-time embedded platform), which can support the real time Java in a resource constrained environment. The key technologies are deeply studied and the.HJrep Java processor is used as the execution engine, and the Java byte code is used as the local instruction. The main innovative works of this paper include:
(1) a runtime predicable non heap memory model is proposed for the hard Java real-time embedded platform. This model eliminates the impact of security access check on the real-time performance of the system. Without changing the Java syntax and programming mode, it preserves the support for multithread sharing and nesting of non heap memory.
(2) a set of single parent rule checking algorithm and assignment rule checking algorithm based on static analysis is proposed. The algorithm can perform static rule checking before the system runs, and it does not affect the running time system, and avoids the running time cost and real time effect of dynamic analysis and inspection.
(3) an improved subgenerational garbage collector is designed for the hard Java real time embedded platform. The collector provides a high efficient and low cost recovery strategy for target environment memory management for target environment features. It effectively avoids the frequent secondary collection and suspension, avoids the moving overhead and memory fragmentation of the objects collected in the mature space. In view of garbage collection, an object reference model for hard Java real-time embedded platform is designed. This model provides effective support for object tracking, heap space scanning, synchronization and so on.
(4) a high efficient and predictable method of method call implementation is designed for hard Java real time embedded platform, which ensures the prediction of the running time of the method call, improves the execution efficiency of the method call and reduces the execution cycle of the method call.
【學(xué)位授予單位】：復(fù)旦大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2012
【分類號】：TP368.1

【共引文獻(xiàn)】

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1 劉錦錦;基于struts框架的web網(wǎng)站開發(fā)及數(shù)據(jù)分析[D];北京化工大學(xué);2005年

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