Dynamic Web Pages In Java: How To Create Web Pages In Java?

CGI (Common Gateway Interface), is an application used to generate dynamic content of web pages. A common gateway interface can be created using any programming language such as c, c++, etc.

While using CGI, the web server sequentially performs the following tasks when the client requests something: –

• It receives the request and the required CGI.
• Creates a new process and invokes the required CGI application.
• CGI generates the output and after getting the information of the client’s request.
• It sends the output (response) to the web server and destroys the process.
• The web server shows it the client’s screen.

In CIG, a new process must be created and destroyed for each request, as the number of clients increases, the workload also increases and therefore less power and time for the Processing requests are also increasing because CGI cannot communicate directly with the web server. To overcome its limitations, servlets are introduced.

Servlets are cheaper than CGI and can handle cookies. The Java servlet follows a simple process shown in the following block diagram:-

Steps

• A client sends the request to a web server .
• The web server receives the request from the client.
• Servlets receive the request.
• Servlets receive the request.
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  • Servlets process the request and generate the output.
  • Servlet sends the output to the web server.
  • A web server sends it to the client’s browser and the browser displays it on the client’s screen.

  There are two packages that can be used to build servlets

  • javax.servlet(Basic)
  • javax. servlet.http(Advance)

  Advantages of Servlets

  • They are platform independent.
  • They are cheaper than CGI.
  • You can handle cookies.
  • They overcome the limitations of CGI.
  • NO need to create a new process for each request.
  • Since it is a server-side application, it can inherit the security of a web server.

  Let’s move to the next topic of this article on web pages in Java,

  What is a servlet container

  Users didn’t have the option to request and access the static pages, but also dynamic ones, with dynamic web pages each time for different inputs and may work differently over time.

  A servlet container is nothing but a concept or idea to use the

  Java language to build dynamic web pages (servlet ) to develop.

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  The servlet container is a part of the web server that can easily communicate with the Java servlets.

  There are three main methods that can be called by the client as needed:-

  • Init()
  • Service()
  • Destroy()

  Web pages in Java Our first servlet program

  To be developed at our first servlet application follows three steps

  First we need to create an HTML page that will require a request from the servlet.

  This page will only have one Invoke MyFirstServlet button. Clicking this button calls MyFirstServlet. Now let’s create a servlet in which we will implement three methods:-

  • Init()
  • Service()
  • Destroy( )

  Import javax,servlet. *; import java.io.*; The public class OurFirstServlet implements Servlet{ ServletConfig config=null; Public void init(ServletConfig sc) { Config = sc; System.out.println(“in init”); } public void service (ServletRequest req, ServletResponse res) throws ServletException, IOException { res.setContenttype(“text/html”); PrintWriter pw = res.getWriter(); pw.println(“

  Hello from servlet

  “); System.out.println(“in operation”); maintained } public String getServletInfo() { return “MyFirstServlet”; } public ServletConfig getServletConfig() { return config; }

  In lines 1 and 2 we import two packages, the second one is for PrintWriter.

  In line 3 we create a servlet by implementing a servlet interface.

  In the first line within a class, we create a ServletConfig object configuration that contains the configuration of the servlet. Initially it is set to null because there is no servlet.

  Then we created an init method that accepts an object of type ServletConfig sc . This is called when a request comes to the servlet. This is used to initialize the configuration object.

  There is a Destroy() that is used to mark the end of the servlet.

  The getServletInfo() is used to return the name of the Servlet

  The getServletConfig returns the Config object when invoked.

  Finally , after a request has come, creates two objects of type ServletRequest and ServletResponse to mark their connection with the client and pass them to service(). Here we set the response type of our ServletResponse object to HTML type. Then we get the PrintWriter object pw from the response object res by calling getWriter(). Finally, we use println() of the pw object to write what we need to print as a response to the client.

  This brings us to the end of this article on “Web Pages in Java”. If you want to learn more, take the Java Certification Course from Edureka, a trusted online learning company. Edureka’s Java J2EE and SOA Training and Certification course is designed to train you on both basic and advanced Java concepts along with various Java frameworks such as Hibernate and Spring.

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