Distributed Web Service - Assignment Example

Distributed Web Service 1. Introduction The distributed application I have developed provides web services using different development environment and tools. C# is the programming I used, as it is simple and safe programming language that was built specifically for rich development platforms like .NET exploitable with various language and tools. More importantly, it also allows the database interaction requirements of my web service application. The application developed enables the user to retrieve student’s information from a database, such as student id, title, forename, and surname. It is capable of deleting customer from the database and display items and particular student’s information. In other words, I have created a web service to act as front-end for a SQL database, which will respond to arbitrary SQL queries. In view of the recently developed application, the following are evaluation of the tools, languages, and platforms used to implement the application and details of the development process undertaken. 2. The Web Service A Web Service is a form of client/server systems structured to make as much use as possible of Web standards. In the most common configurations, a Web Services is actually a front-end to a database server or some other enterprise serves or to a collection of them, functioning as an intermediary between client application and a legacy system managed by the enterprise. However, there other possible Web Service configuration, for instance, Microsoft has explored supporting Web Service interfaces to a great variety of servers used internally by the Windows XP and .NET platform where the server would often be a rather small program or even a system module. The simplest Web Services systems consist of a small set of components. These are Request Dispatch Module, which has a router that accepts connections normally in the form of TCP connection on which HTTP will be used to issue the actual requests. The request will be encoded using the SOAP standard, and dispatches the request to an appropriate server or other back-end process. Normally, the server will be external to the request dispatcher, although perhaps on the same computing platform. A Web Service Description Language (WSDL) document provides clients and other Web Services applications and tools with a description of the Web Service. This type of language uses XML to represent actually the information. One the standard operation possible on a Web Service is to fetch its WSDL document. A Web Service is then a form of a computer-accessible front end that at the minimum, have a description of the available services encoded as WSDL document and support access via a protocol called SOAP, the Standard Object Access Protocol (Birman 2005, 54). 3. Distributed Systems In most distributed systems, services can be instantiated multiple times, for instance, a distributed system can contain multiple file servers, or multiple name serves. We normally use the term ‘service’ to denote a set of servers. Therefore, the ‘network file system service’ consists of the network file servers for a system, and the ‘network information service’ is a set of servers, provided on UNIX and Linux systems, that maps symbolic names to ASCII strings encoding values or addresses. Distributed system is concern about binding of applications to servers. Binding occurs when a process that needs to talk to a distributed service becomes associated with a specific server that will perform request on its behalf. Web Services have a standardized binding mechanism. In some model, the client system will normally start by searching for the desired service in some form of name space. Highly functional Web Services applications could transform that way that companies do business, creating a new kind of ‘real-time enterprise’ in which computers interacting over Web Services become a standard for doing just about anything one might wish to do in a distributed setting. With much greater interoperability and integration that is possible in today’s world of proprietary standards and home-brew interconnects (Birham 2005, 161) 4. C# Development The premise of the .NET Framework is that all languages are created equal. C# is an excellent language for .NET development. It is extremely versatile, robust, and well-designed language. On the other hand, Java Programmers may look at C# with a mixture of trepidation, glee, and resentment as it has been suggested that C# is somehow a cheat of Java. C# offers an easy transition for Java programmers as the syntax is very similar and the semantics are familiar and comfortable. The goal of C# is to provide a simple, safe, modern, object-oriented, internet-centric, high-performance language for .NET development. C# is new but it draws on the lesson learned over the past three decades. This language is disarmingly, simple, with only about 80 keywords and a dozen built-in data types, but C# is highly expressive when it comes to implementing modern programming concepts. C# includes all the support for structures, component-based, object-oriented programming that one expects of a modern language built on the shoulders of C++ and Java. At the heart of any object-oriented language is its support for defining and working with classes. Classes define new types, allow you to extend the language to better model the problem you are trying to solve. C# contains keywords for declaring new classes and their methods and properties, and for implementing encapsulation, inheritance, and polymorphism, the three pillars of object-oriented programming. In C#, everything pertaining to a class declaration is found in the declaration itself. C# class definition do not require separate header files or Interface Definition Language *(IDL) files. Moreover, C# supports a new XML style of inline documentation that simplifies the creation of online and print reference documentation for an application (Liberty 2003, 6). It supports interfaces, a means of making a contact with a class for services that the interface stipulates. Here, a class can inherit from only a single parent, but a class can implement multiple interfaces. C# also provides support for structs, a concept whose meaning has changed significantly from C++. In C#, a struct is a restricted, lightweight type that, when instantiated, makes fewer demands on the operating system and on memory than a conventional class does. A struct cannot inherit from a class or inherited from, but a struct can implement an interface (Liberty 2003, 7). C# provides component-oriented features, such as properties, events, and declarative constructs called attributes. Component-oriented programming is supported by the CLR’s support for storing metadata with the code for the class. The metadata describes the class, including its method and properties, as well as its security needs and other attributes, such as whether it can be serialized where the code contains the logic necessary to carry out its functions. A compiled class is thus a self-contained unit. Therefore, a hosting environment that knows how to read a class’ metadata and code needs not other information to make use of it. Using C# and CLR, it is possible to add custom metadata to a class by creating custom attributes. Likewise, it is possible to read class metadata using CLR types that support reflection. More importantly, and as a final word about C#, it also provides support for directly accessing memory using C++ style pointers and keywords for bracketing such operations as unsafe, and for warning the CLR garbage collector not to collect object referenced by pointers until they are released (Liberty 2003, 8). A few disadvantages of C# compared to other version of C like C++, if a break or goto is missing from a nonempty case statement, the compiler issues an error. In C++, the execution is said to fall through from a case to the case below it and continue with the next case. C# naturally does not support fall through as it attempts to employ a more formal abstraction, where the cases are truly distinct and disconnected entities (Wills 2006, 36). C# is case sensitive, unlike Visual Basic; the C# development environment will not fix your case mistakes (Liberty 2003, 25) 5. .NET Framework The .NET platform is a managed, language-independent platform for building and running applications. There are two primary components of the .NET platform, CLR and FCL, the Common Language Runtime and the .NET framework class library (Hladni 2006, 657). .NET platform provide a common playing field for all languages to seamlessly interoperate with a common type system and base class library. Along with this new platform, Microsoft has created a language specifically designed to take advantage of the .NET platform, C# (Powel et. al. 2001, 8). As we mentioned earlier, a Web Service is an application or block of executable code that is hosted on web server and whose functions are exposed through standard XML protocols. .NET framework services make it easy to find this code, invoke it, and retrieve a result. In fact, calling a .NET we service is just as easy as calling a local function. A .NET Web Service is however not an object in a traditional sense. Web Services are designed to overcome the limitation of these earlier technologies and with .NET creating and consuming web services is possible. .NET is an open standard; it has cross platform capabilities, and straightforward (Ferrara and MacDonald 2002, 16). 6. Apache Creating web services is different programming language but the process is essential the same. The APACHE SOAP is the Apache Software Foundation’s implementation of the SOAP protocol. It is designed to run as a servlet within any Java HTTP Server. As such, it implements only the proxy part of the message handling process. Apache SOAP’s list of features is impressive, sharing many of the same benefits as it Perl-based counterpart (Snell et. al. 2002, 45). As its core, Apache is about communication over networks. Apache uses the TCP/IP protocol as its foundation, providing implementation of HTTP. It is a program runs under a suitable multitasking operating system such as UNIX and Windows. It suites sites of all sizes and types. One can run a single personal page on it or an enormous site serving millions of regular visitors. Use it to serve static files over the Web or as a front end to applications that generate customized responses to visitors. Apache can be an appropriate solution for practically any situation involving the HTTP protocol (Laurie and Laurie 2002, 3). 7. Web Service Client and Apache Tomcat Client communicates with Web Services using standard web protocols. With the use of XML encoded messages to send and receive messages, makes it possible for client applications running on any platform to access web services as long as they are using web standard protocols. Tomcat is Java servlet container and web server form the Jakarta project of the Apache Software Foundation. Web servers in general are not only limited to serving up static HTML pages, they can also run programs in response to user requests and return the dynamic results to the user’s browser. This is an aspect of the web that Apache’s Tomcat is very good at because it provides both Java servlet and JavaServer Pages (JSP) technologies. Consequently, Tomcat is a good choice for use as web server for many applications. However, integrating Tomcat with Apache httpd configuration has its won disadvantage. For instance, Apache httpd response to HTTP request is slower than Tomcat in almost all use cases. However, when Apache httpd had to relay Tomcat’s request and responses, Tomcat standalone was 51% to 257% faster versus the same request traffic contacting Tomcat only through Apache httpd and a connector module. More importantly, authentication and access control are not shared between httpd and Tomcat, which is a problem with all methods of integrating Tomcat with httpd. (Brittain and Darwin 1995, 184). 8. Further Improvements Although a lot of preparation and research have been done to come up with a web service application, I am aware that my application still needs some more improvement considering the fact that it may not work as expected in an actual client/server environment. Furthermore, I am confident that there is a much better approach and I will in the near future investigate further to come up with a much better design and probably much better tools. Note: Please generate your development log and paste it here 9. Reference List Birman Kenneth P., 2005, Reliable Distributed Systems: Technologies, Web Services, and Applications, Published 2005 Springer, ISBN: 0387215093 Brittain Jason and Darwin Ian, 2002, Tomcat: The Definitive Guide, Published O’Reilly 2002, ISBN: 0596003188 Ferrara Alex and MacDonald Matthew, 2002, Programming .NET Web Services, Published 2002 O'Reilly, ISBN: 0596002505 Hladni Ivan, 2006, Inside Delphi 2006, Published 2006 Wordware Publishing, Inc, ISBN: 1598220039 Laurie Ben and Laurie Peter, 2002, Apache: The Definitive Guide, Published 2002 O'Reilly, ISBN: 0596002033 Liberty Jesse, 2003, Programming C#, Published 2003 O'Reilly, ISBN: 0596004893 Powell Bob, Powell Robert, and Weeks Richard, 2001, C# and the .Net Framework: The C++ Perspective, Published 2001 Sams Publishing, ISBN: 067232153X Snell James, Tidwell Doug, and Kulchenko Pavel, 2002, Programming Web Services with SOAP, Published 2002 O'Reilly, ISBN: 0596000952 Wills Dean, 2006, Pro Visual C++ 2005 for Developers: Featuring C++/CLI, Published 2006 Apress, ISBN: 1590596080         Read More