Frameworks

CompSci 230 S2 2013Software Construction

Agenda & Reading Topics:

Frameworks Extensibility Inversion of Control Java Frameworks Advantages & Disadvantages

Reading Software framework Wikipedia Frameworks in Java

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Framework Generic software platform for a certain type of

applications Consists of parts that are found in many apps of that type

Libraries with APIs (classes with methods etc.) Ready-made extensible programs ("engines") Sometimes also tools (e.g. for development, configuration, content)

Often evolved by developing many apps of that type and reusing code more and more

Characteristics: Reusable: the parts can be used for many apps of that type Extensible: developers can add their own app-specific code Inversion of Control: framework often calls your code

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Framework Examples

Web Application Frameworks

GUI Toolkits

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Extensibility All frameworks can be extended to cater for app-

specific functionality. A framework is intended to be extended to meet the

needs of a particular application Common ways to extend a framework:

Extension is carried out by sub-classing, overriding methods, and implementing interfaces

Plug-ins: framework can loadcertain extra code in a specific format

Within the framework language: Subclassing & overriding methods Implementing interfaces Registering event handlers

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Inversion of Control A framework employs an inverted flow of control

between itself and its clients. When using a framework, one usually just implements a few

callback functions or specializes a few classes, and then invokes a single method or procedure.

The framework does the rest of the work for you, invoking any necessary client callbacks or methods at the appropriate time and place.

i.e. "Don't call us, we'll call you.“, or "Leave the driving to us.“

Example: Java's Swing and AWT classes. They have a huge amount of code to manage the user

interface, and there is inversion of control because you start the GUI framework and then wait for it to call your listeners

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Inversion of Control Traditional Program Execution Inversion of Control

The app has control over the execution flow,

calling library code when it needs to.

The framework has control over the execution flow, calling app code for app-

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Inversion of Control Example: Java Applets

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What is Java Frameworks? Frameworks are large bodies (usually many

classes) of prewritten code to which you add your own code to solve a problem in a specific domain.

In Java technology there are so many frameworks that helps the programmers to build complex applications easily. Examples: GUI Framework: eg Java's Swing and AWT classes Collection Framework/library

It is a unified architecture for representing and manipulating collections

It contains Interfaces, Implementations and algorithms

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Collections Framework The Java Collections Framework provides the

following benefits: Reduces programming effort

Concentrate on the important parts of your program rather than on the low-level "plumbing" required to make it work.

Increases program speed and quality It provides high-performance, high-quality implementations

of useful data structures and algorithms Fosters software reuse

New data structures that conform to the standard collection interfaces are by nature reusable. The same goes for new algorithms that operate on objects that implement these interfaces.

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Frameworks VS libraries Framework uses your code because it is usually

the framework that is in control. It means the framework controls the sequence and

logic of some operation and calls your code to provide certain details

You make use of a framework by calling its methods, inheritance, and supplying "callbacks", listeners, etc

Note: although sometimes large libraries are referred to as frameworks, this is probably not the most common use of the term.

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Advantages Reuse can save cost and time Higher level of abstraction

Frameworks provides a standard working system through which user can develop the desired module of application or complete application instead of developing lower level details.

Developers can devote more time in developing the software requirement

Reduced maintenance cost (if the framework is maintained by someone else)

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Disadvantages Can lead to code bloat

Framework may contain lots of unused code May need to use several frameworks

Cost of learning a framework Spend more time in assessing the concept, function

and its uses in developing the program. Licensing cost (for commercial frameworks) A generic ‘one-size-fits-all’ does not work so

efficiently for any specific software. There is need to extend framework with specific code to develop any specific software.

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