Systems Analysis and Design - Assignment Example

 Systems Analysis and Design Introduction Camberwell is one of the world’s famous art and design institutions, which welcomed students to South London for over a century, many of whom have stayed on in the area making it the place for artists to live and work. The Camberwell College of Arts, which includes Icon Gallery, has an international reputation for high quality teaching by leading practitioners – teaching that has put artists and designers on the road to international prominence and many others on the path to fulfilment in their chosen practice. Following significant expansion the Gallery is undertaking a major review of their informatics system and decided to enhance the system developing Case Scenarios and Java encoding systems Examples of Case Scenario in accordance with UML 2.0 and generalities about Java Programming are given below. The syntax of Java is largely derived from C++. Unlike C++, which combines the syntax for structured, generic, and object-oriented programming, Java was built almost exclusively as an object-oriented language. All code is written inside a class, and everything is an object, with the exception of the intrinsic data types (ordinal and real numbers, boolean values, and characters), which are not classes for performance reasons. Java suppresses several features (such as operator overloading and multiple inheritance) for classes in order to simplify the language and to prevent possible errors and anti-pattern design. Java uses similar commenting methods to C++. There are three different styles of comment: a single line style marked with two slashes (//), a multiple line style opened with a slash asterisk (/*) and closed with an asterisk slash (*/), and the Javadoc commenting style opened with a slash and two asterisks (/**) and closed with an asterisk slash (*/). The Javadoc style of commenting allows the user to run the Javadoc executable to compile documentation for the program. Example: // This is an example of a single line comment using two slashes /* This is an example of a multiple line comment using the slash and asterisk. This type of comment can be used to hold a lot of information or deactivate code but it is very important to remember to close the comment. */ * This is an example of a Javadoc comment; Javadoc can compile documentation * from this text. */ The traditional Hello world program can be written in Java as: // Outputs "Hello, world!" and then exits public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, world!"); To compare this to other programming languages see the list of hello world program examples. Source files must be named after the public class they contain, appending the suffix .java, for example, HelloWorld.java. It must first be compiled into bytecode, using a Java compiler, producing a file named HelloWorld.class. Only then can it be executed, or 'launched'. The java source file may only contain one public class but can contain multiple classes with less than public access and any number of public inner classes. A class that is not declared public may be stored in any .java file. The compiler will generate a class file for each class defined in the source file. The name of the class file is the name of the class, with .class appended. For class file generation, anonymous classes are treated as if their name were the concatenation of the name of their enclosing class, a $, and an integer. The keyword public denotes that a method can be called from code in other classes, or that a class may be used by classes outside the class hierarchy. The class hierarchy is related to the name of the directory in which the .java file is located. The keyword static in front of a method indicates a static method, which is associated only with the class and not with any specific instance of that class. Only static methods can be invoked without a reference to an object. Static methods cannot access any method variables that are not static. The keyword void indicates that the main method does not return any value to the caller. If a Java program is to exit with an error code, it must call System.exit() explicitly. The method name "main" is not a keyword in the Java language. It is simply the name of the method the Java launcher calls to pass control to the program. Java classes that run in managed environments such as applets and Enterprise JavaBean do not use or need a main() method. A java program may contain multiple classes that have main methods, which means that the VM needs to be explicitly told which class to launch from. The main method must accept an array of String objects. By convention, it is referenced as args although any other legal identifier name can be used. Since Java 5, the main method can also use variable arguments, in the form of public static void main(String... args), allowing the main method to be invoked with an arbitrary number of String arguments. The effect of this alternate declaration is semantically identical (the args parameter is still an array of String objects), but allows an alternative syntax for creating and passing the array. The Java launcher launches Java by loading a given class (specified on the command line or as an attribute in a JAR) and starting its public static void main(String[]) method. Stand-alone programs must declare this method explicitly. The String[] args parameter is an array of String objects containing any arguments passed to the class. The parameters to main are often passed by means of a command line. Printing is part of a Java standard library: The System class defines a public static field called out. The out object is an instance of the PrintStream class and provides many methods for printing data to standard out, including println(String) which also appends a new line to the passed string. The string "Hello, world!" is automatically converted to a String object by the compiler. The Hello class extends (subclasses) the JApplet (Java Applet) class; the JApplet class provides the framework for the host application to display and control the lifecycle of the applet. The JApplet class is a JComponent (Java Graphical Component) which provides the applet with the capability to display a graphical user interface (GUI) and respond to user events. The Hello class overrides the paintComponent(Graphics) method inherited from the Container superclass to provide the code to display the applet. The paintComponent() method is passed a Graphics object that contains the graphic context used to display the applet. The paintComponent() method calls the graphic context drawString(String, int, int) method to display the "Hello, world!" string at a pixel offset of (65, 95) from the upper-left corner in the applet's display. Hello World Applet An applet is placed in an HTML document using the HTML element. The applet tag has three attributes set: code="Hello" specifies the name of the JApplet class and width="200" height="200" sets the pixel width and height of the applet. Applets may also be embedded in HTML using either the object or embed element, although support for these elements by Web browsers is inconsistent. However, the applet tag is deprecated, so the object tag is preferred where supported. The host application, typically a Web browser, instantiates the Hello applet and creates an AppletContext for the applet. Once the applet has initialized itself, it is added to the AWT display hierarchy. The paintComponent() method is called by the AWT event dispatching thread whenever the display needs the applet to draw itself. Servlet Java Servlet technology provides Web developers with a simple, consistent mechanism for extending the functionality of a Web server and for accessing existing business systems. Servlets are server-side Java EE components that generate responses (typically HTML pages) to requests (typically HTTP requests) from clients. A servlet can almost be thought of as an applet that runs on the server side—without a face. // Hello.java import java.io.*; import javax.servlet.*; public class Hello extends GenericServlet { public void service(ServletRequest request, ServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); final PrintWriter pw = response.getWriter(); pw.println("Hello, world!"); pw.close(); } }The import statements direct the Java compiler to include all of the public classes and interfaces from the java.io and javax.servlet packages in the compilation. The Hello class extends the GenericServlet class; the GenericServlet class provides the interface for the server to forward requests to the servlet and control the servlet's lifecycle. The Hello class overrides the service(ServletRequest, ServletResponse) method defined by the Servlet interface to provide the code for the service request handler. The service() method is passed a ServletRequest object that contains the request from the client and a ServletResponse object used to create the response returned to the client. The service() method declares that it throws the exceptions ServletException and IOException if a problem prevents it from responding to the request. The setContentType(String) method in the response object is called to set the MIME content type of the returned data to "text/html". The getWriter() method in the response returns a PrintWriter object that is used to write the data that is sent to the client. The println(String) method is called to write the "Hello, world!" string to the response and then the close() method is called to close the print writer, which causes the data that has been written to the stream to be returned to the client. JavaServer Pages JavaServer Pages (JSP) are server-side Java EE components that generate responses, typically HTML pages, to HTTP requests from clients. JSPs embed Java code in an HTML page by using the special delimiters . A JSP is compiled to a Java servlet, a Java application in its own right, the first time it is accessed. After that, the generated servlet creates the response. Swing application Swing is a graphical user interface library for the Java SE platform. It is possible to specify a different look and feel through the pluggable look and feel system of Swing. Clones of Windows, GTK+ and Motif are supplied by Sun. Apple also provides an Aqua look and feel for Mac OS X. Where prior implementations of these looks and feels may have been considered lacking, Swing in Java SE 6 addresses this problem by using more native GUI widget drawing routines of the underlying platforms. This example Swing application creates a single window with "Hello, world!" inside: // Hello.java (Java SE 5) import javax.swing.*; public class Hello extends JFrame { public Hello() { super("hello"); setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); add(new JLabel("Hello, world!")); pack(); public static void main(String[] args) { new Hello().setVisible(true); The first import includes all of the public classes and interfaces from the javax.swing package. The Hello class extends the JFrame class; the JFrame class implements a window with a title bar and a close control. The Hello() constructor initializes the frame by first calling the superclass constructor, passing the parameter "hello", which is used as the window's title. It then calls the setDefaultCloseOperation(int) method inherited from JFrame to set the default operation when the close control on the title bar is selected to WindowConstants.EXIT_ON_CLOSE — this causes the JFrame to be disposed of when the frame is closed (as opposed to merely hidden), which allows the JVM to exit and the program to terminate. Next, a JLabel is created for the string "Hello, world!" and the add(Component) method inherited from the Container superclass is called to add the label to the frame. The pack() method inherited from the Window superclass is called to size the window and lay out its contents. The main() method is called by the JVM when the program starts. It instantiates a new Hello frame and causes it to be displayed by calling the setVisible(boolean) method inherited from the Component superclass with the boolean parameter true. Once the frame is displayed, exiting the main method does not cause the program to terminate because the AWT event dispatching thread remains active until all of the Swing top-level windows have been disposed. ti-line comment tags, Javadoc comments have an extra asterisk at the beginning, so that the tags are /** and */. Sun has defined and supports four editions of Java targeting different application environments and segmented many of its APIs so that they belong to one of the platforms. The platforms are: Java Card for smartcards. Java Platform, Micro Edition (Java ME) — targeting environments with limited resources. Java Platform, Standard Edition (Java SE) — targeting workstation environments. Java Platform, Enterprise Edition (Java EE) — targeting large distributed enterprise or Internet environments. The classes in the Java APIs are organized into separate groups called packages. Each package contains a set of related interfaces, classes and exceptions. Refer to the separate platforms for a description of the packages available. References 1 ^ "TIOBE Programming Community Index". 2009. http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html. Retrieved 2009-05-06.  2 ^ Byous, Jon (ca. 1998). "Java technology: The early years". Sun Developer Network. Sun Microsystems. Archived from the original on April 20, 2005. http://web.archive.org/web/20050420081440/http://java.sun.com/features/1998/05/birthday.html. Retrieved 2005-04-22.  3 ^ "The History of Java Technology". Sun Developer Network. ca. 1995. http://www.java.com/en/javahistory/. Retrieved 2010-04-30.  4 ^ "Jonathan Schwartz's Blog: Different Isn't Always Better, But Better's Always Different". Blogs.sun.com. http://blogs.sun.com/jonathan/entry/better_is_always_different. Retrieved 2010-06-09.  5 ^ Heinz Kabutz, Once Upon an Oak. Artima. Retrieved April 29, 2007. Read More