Design Pattern Implementation In Java And Aspectj Pdf


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Design Patterns Vs Aspect Oriented Programming–A Qualitative and a Quantitative Assessment

An aspect weaver is a metaprogramming utility for aspect-oriented languages designed to take instructions specified by aspects isolated representations of significant concepts in a program and generate the final implementation code. The weaver integrates aspects into the locations specified by the software as a pre- compilation step. By merging aspects and classes representations of the structure of entities in the program , the weaver generates a woven class.

Aspect weavers take instructions known as advice specified through the use of pointcuts and join points , special segments of code that indicate what methods should be handled by aspect code.

The implementation of the aspect then specifies whether the related code should be added before, after, or throughout the related methods. By doing this, aspect weavers improve modularity , keeping code in one place that would otherwise have been interspersed throughout various, unrelated classes.

Many programming languages are already widely accepted and understood. However, the desire to create radically different programming languages to support the aspect-oriented programming paradigm is not significant due to business-related concerns; there are risks associated with adopting new technologies. Additionally, the existing code base of a business would need to be discarded.

Finally, a business would need to acquire a new toolchain suite of tools for development, which is often both an expense in both money and time. To address these business concerns, an aspect weaver enables the use of widely adopted languages like Java with aspect-oriented programming through minor adaptations such as AspectJ which work with existing tools.

This ensures that any existing object oriented code will still be valid aspect-oriented code and that development will feel like a natural extension of the object-oriented language. Aspect weavers operate by taking instructions specified by aspects , known as advice , and distributing it throughout the various classes in the program automatically.

The result of the weaving process is a set of classes with the same names as the original classes but with additional code injected into the classes' functions automatically. The advice specifies the exact location and functionality of the injected code. Through this weaving process, aspect weavers allow for code which would have otherwise been duplicated across classes.

By eliminating this duplication, aspect weavers promote modularity of cross-cutting concerns. During weaving, the aspect weaver uses the pointcuts and join points, known as a pointcut designator , to identify the positions in candidate classes at which the implementation should be injected. In the programming language AspectJ , pointcuts, join points, and the modularized code are defined in an aspect block similar to that of Java classes.

Classes are defined using Java syntax. The weaving process consists of executing the aspect advice to produce only a set of generated classes that have the aspect implementation code woven into it. The example at right shows a potential implementation of an aspect which logs the entry and exit of all methods. Without an aspect weaver, this feature would necessitate duplication of code in the class for every method.

Instead, the entry and exit code is defined solely within the aspect. The aspect weaver analyzes the advice specified by the pointcut in the aspect and uses that advice to distribute the implementation code into the defined class. The code differs slightly in each method due to slight variances in requirements for the method as the method identifier has changed.

The aspect weaver determines the appropriate code to generate in each situation as defined by the implementation advice and then injects it into methods matching the specified pointcut. Instead of generating a set of woven source code , some AspectJ weavers instead weave the aspects and classes together directly into bytecode , acting both as the aspect weaver and compiler.

However, the bytecode weaving process produces more efficient runtime code than would usually be achieved through compiled woven source. Developments in AspectJ have revealed the potential to incorporate just-in-time compilation into the execution of aspect-oriented code to address performance demands. To accomplish just-in-time weaving, a change to the virtual machine that executes the compiled bytecode is necessary.

A proposed solution for AspectJ uses a layered approach which builds upon the existing Java Virtual Machine to add support for join point management and callbacks to a Dynamic Aspect-Oriented Programming Engine. Aspect weavers' performance, as well as the performance of the code that they produce, has been a subject of analysis. It is preferable that the improvement in modularity supplied by aspect weaving does not impact run-time performance.

Aspect weavers are able to perform aspect-specific optimizations. For example, AspectJ contains two similar but distinct keywords, thisJoinPoint , which contains information about this particular instance of woven code, and thisJoinPointStaticPart , which contains information common to all instances of code relevant to that set of advice.

The optimization of replacing thisJoinPoint with the more efficient and static keyword thisJoinPointStaticPart can only be done by the aspect weaver.

By performing this replacement, the woven program avoids the creation of a join point object on every execution. Compile-time performance is generally worse in aspect weavers than their traditional compiler counterparts due to the additional work necessary for locating methods which match the specified pointcuts.

From Wikipedia, the free encyclopedia. Aspect weaver An aspect weaver takes information from raw classes and aspects and creates new classes with the aspect code appropriately weaved into the classes. Semantics of Static Pointcuts in AspectJ. Retrieved 23 January Retrieved 27 January Hilsdale, Erik; Hugunin, Jim Archived from the original PDF on 27 July Communications of the ACM.

June Lecture Notes in Computer Science. Archived from the original PDF on Retrieved 4 January McEachen, Nathan; Alexander, Roger Archived from the original PDF on 13 October Spinczyk, Olaf; Lohmann, Daniel October Knowledge-Based Systems. Viega, John; Voas, Jeffrey November IEEE Software. Archived from the original PDF on 25 August Wang, Yi; Zhao, Jianjun July Aspect-oriented software development.

Categories : Aspect-oriented programming Aspect-oriented software development Compiler construction Programming language implementation. Hidden categories: Good articles All articles with dead external links Articles with dead external links from July Articles with permanently dead external links Articles with example Java code. Namespaces Article Talk.

Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version. An aspect weaver takes information from raw classes and aspects and creates new classes with the aspect code appropriately weaved into the classes. Aspect-oriented programming. A sample aspect and class defined in the AspectJ programming language.

Design Patterns Vs Aspect Oriented Programming–A Qualitative and a Quantitative Assessment

A reflection of the modularity and crosscutting improvements made to design patterns by developing them in AspectJ. View PDF. This essay is a response to the paper:. Cross-Cutting and Aspects. Aspect orientated programming involves the separation of concerns within an application so that they do not clutter or cut across one other.

Aspect weaver

References post fixed with a date indicates the date they were retrieved, in the format dd. Note that the bibliography has been updated to reflect thesis changes made after grading. January , Gunni Rode. Brown , Raphael C.

Design patterns as aspects: a quantitative assessment. Design patterns offer flexible solutions to common problems in software development. Recent studies have shown that several design patterns involve crosscutting concerns.

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Design Patterns: Elements of Reusable Object-Oriented Software is a software engineering book describing software design patterns. The book is divided into two parts, with the first two chapters exploring the capabilities and pitfalls of object-oriented programming, and the remaining chapters describing 23 classic software design patterns. It has been influential to the field of software engineering and is regarded as an important source for object-oriented design theory and practice. More than , copies have been sold in English and in 13 other languages. The authors are often referred to as the Gang of Four GoF. They were later joined by Ralph Johnson and John Vlissides.

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Design pattern implementation in Java and aspectJ

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