Research On Exception Handling Key Technologies Of Service-oriented Computing

With the service oriented architecture (SOA) and Services Computing technologies (SOC) becoming a hot spot in the field of software engineering research and practice at home and abroad, the research of exception handling technologies of service computing has received wide attention from both academia and industry. As an important means to improve the availability and reliability of the system, the exception handling technologies can make the system running normally and complete its intended functions when part of the services is in failure. Therefore, a set of exception handling mechanism of service computing is very important to improve the dependability of the service oriented application. With services computing, a new computing paradigm has changed the form of software, which makes it more challenging for exception handling. How to construct available and reliable software system using services computing theory and exception handling technologies is an important research topic with great significance and practical value.Although lots of research achievements on exception handling technology of services computing have been made, we are still faced with many challenges and problems to be solved. Focused on these problems, the main research contents are as follows:Aiming at the existing problems that formal description approach of services computing exception are too cumbersome and complex, formal description approaches for exception handling processes, strategies and conditions based on predicate logic are put forward, and combined with the state transition diagram and ECA rules to visually express the exception handling process, it is conducive to understand and implement the complex exception handling logic. As a basis for formal description of service computing exception handling, some basic exception handling strategies are designed based on defining the concepts of service and abnormal, and applying the method of state transition diagram combining with ECA rules to describe these basic strategies. Finally, when the designed exception handling strategies is applied in exception handling cases, it can be verified that these strategies are effective in exception recovery process.Aiming at the existing problems that services computing modeling and modeling language in support of exception handling is weak, the exception handling modeling language for service oriented computing (CCML-E) is put forward. By extending the ports of the cooperative service computing model, the control flow rules, ports binding rules and the process-based structure, the CCML-E can be established. After the design of CCML-E based on service-oriented computing and design for the elements of language such as exception type, exception capture and handling statement, throw exception statement etc., CCML-E has the capacity of exception handling. CCML-E exception processing mechanism was designed by referring to Java language. Represented by the format based on XML and compared to text format, with the characteristic of readability, format, and platform independent, CCML-E is easy to realize the implement and execution of the CCML-E program.Aiming at the problems existing in the study of service computing exception handling that lack of the support to the forewarning, forecasting and processing when service unavailable exception occurs, a detection and processing method for service unavailable exception based on the deep analysis of the service unavailable exception is presented. Service description model OSDL based on OCL is proposed to overcome the insufficient of description on the service behavior constraint and non-functional attribute information of the general service description model. By means of establishing the exception notification model, the system which make use of the service will be noticed when the service is modified or the business needs are changed, and an effective control of service dynamic change will be achieved. While using the OSDL service description model, we can realize the prediction and avoid the exception of service unavailable by matching the function and non-functional attributes of the business needs rules and service to finish the exception of service availability. Therefore, a processing model of service unavailable exception is designed to equivalently substitute the service unavailable, which can recover the service process at minimum cost and preserve the results have already been executed as possible.In order to providing modeling support to CCML-E language, a modeling support environment using Java language is realized and integrated with an exception handling architecture which is designed based on CCML-E language for loose coupling. In the service cooperative computing arrangement, when icons for realizing exception handling logic and the visual exception handling structures are added, the framework for exception handling logic can be added in the service visual modeling phase to realize the visual display of exception handling logic. Further, the necessary modeling support environment for service cooperative computing is extended, which can provide the CCML-E language for software infrastructure of program development, exception detection, exception recovery and other core functions including the design of exception handling logic.In order to verify the effectiveness of exception handling method and the feasibility of the exception handling mechanism proposed in this paper, an exception handling modeling case of service-oriented computing is introduced in detail. Applying CCML-E language to descript the business process of the system, the possible exception in the service interaction can be modeled. The capture and processing of the exception can be realized by using the exception handling structure of the CCML-E. The analysis and execution of CCML-E code based on XML format can be achieved by applying Java development environment and DOM4J parser. Through the analysis of the execution results and the verification of the feasibility and effectiveness of the CCML-E exception handling mechanism, the capture and handling of exception can be realized.In this paper, some key technologies of service computing exception handling is discussed, which can provide a reference for solving problems that the service computing exception handling is faced with. It is of great significance to improve the availability and credibility of service oriented applications.