Supporting exception handling for futures in Java

Abstract

A future is a simple and elegant construct that programmers can use to identify potentially asynchronous computation and to introduce parallelism into serial programs. In its recent 5.0 release, Java provides an interface-based implementation of futures that enables users to encapsulate potentially asynchronous computation and to define their own execution engines for futures. In prior work, we have proposed an alternative model, called directive-based lazy futures (DBLFutures), to support futures in Java, that simplifies Java programmer effort and improves performance and scalability of future-based applications. In the DBLFuture model, programmers use a new directive, "@future", to specify potentially concurrent computations within a serial program. DBLFutures enable programmers to focus on the logic and correctness of a program in the serial version first, and then to introduce parallelism gradually and intuitively. Moreover, DBLFutures provide greater flexibility to the Java virtual machine for efficient future support.In this paper, we investigate the exception handling aspect of futures in Java. In Java 5.0 Future APIs, exceptions of future execution are propagated to the point in the program at which future values are queried (used). We show that this exception handling model is not appropriate or desirable for DBLFutures. Instead, we propose an as-if-serial exception handling mechanism for DBLFutures in which the system delivers exceptions at the same point as they would be delivered if the program was executed sequentially. Our approach, we believe, provides programmers with intuitive exception handling behavior and control. We present the design and implementation of our approach within the DBLFuture framework in the Jikes Research Virtual Machine. Our results show that our implementation introduces negligible overhead for applications without exceptions, and guarantees serial semantics of exception handling for applications that throw exceptions.

Understanding Exception Handling: Viewpoints of Novices and Experts

“…One participant compared it to the Spring framework 5 that has made all of its exceptions unchecked, and mentioned that the Spring framework facilitates developers in writing clean code and positive scenario code, but it puts the responsibility on the developer to know what could happen and then handle only things that the developer wants to handle. Two of the participants' answers to the question whether checked exceptions are the real problem are:…”

“…In addition, they propose leveraging aspectoriented programming to enhance the separation between error-handling code and normal code. Zhang et al [5] propose a different approach that provides programmers with more intuitive exception-handling behavior and control. All of these approaches concentrate on enhancing the separation between main functionality code and exception-handling code.…”

Why do developers neglect exception handling?

“…In addition they propose leveraging aspect-oriented programming to enhance the separation between error-handling code and normal code. Zhang and colleagues [10] propose a different approach that provides programmers with more intuitive exception-handling behavior and control.…”

Global-to-Local Approach to Rigorously Developing Distributed System with Exception Handling

“…Also, the CEH mechanism can be implemented at the JVM level to write elegant codes, by applying the approach proposed in [15] which revises the exception mechanism for the new feature "Future" in Java 5.0.…”