Patrones De Software

Writing computer code used to be extremely difficult. When I began programming home computers more years ago than I care to remember, the only way to make a program run at more than a desultory crawl was to write it using machine code. Even a simple word processing utility could take several weeks to create as you meticulously planned the memory allocations for variables, wrote routines to perform simple tasks such as drawing characters on the screen and decoding keyboard input, and then typed every individual processor instruction into an assembler.

Today, by comparison, creating powerful code is easy. We take for granted the wealth of tools, high-level languages, runtime frameworks, code libraries, and operating system services that make it possible to build applications quickly and efficiently. However, while creating the code has become much easier, the task of creating applications has not. We expect much more from our modern applications than ever before. They must communicate over networks, interact with other applications and services, expose highly interactive and responsive user interfaces, and support rich media and graphics. And, of course, they must be robust, secure, reliable, and manageable.

In fact, it would be almost impossible to meet the requirements demanded of our modern applications without the continuing growth and evolution of programming languages, operating systems, platform services, and frameworks. The huge increase in complexity of these applications has also forced us to discover ways to simplify and organize the code. Over the years, a number of tried and tested programming and design techniques have evolved, such as componentization, object-orientation, and—more recently—service orientation.

Patterns and Practices

While improvements in tools and frameworks make it easier to write code more quickly, and modern languages and programming styles make it easier to write better code, the one area that has had the most impact on our ability to create applications over the last 10 to 15 years has been the evolution and increasing acceptance of software design patterns.

Design patterns describe common issues that occur repeatedly in application design and development and provide techniques for handling these issues. Patterns also describe the current industry practice for resolving architectural issues and for handling the design complexity demanded of applications. The arrangement of code and solution elements is at the heart of software design today, and patterns provide us with ways to simplify and organize these elements—providing the best opportunity to maximize performance, flexibility, and maintainability for applications.

Since the release of the ground-breaking book by the Gang of Four, Erich Gamma, Richard Helm, Ralph Johnson, and John M. Vlissides, Design Patterns: Elements of Reusable Object-Oriented Software (Addison-Wesley, 1996), which documented

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