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Servlets URLs can be used in HTML tags. This section shows servlet URLs being used as the destination of an anchor, as the action in a form, and as the location to be used when a METa tag directs that a page be refreshed.

To invoke a servlet from within an HTML page the servlet URL should be used in the appropriate HTML tag. Tags that take URLs include those that begin anchors, forms, and meta tags.

The following is a Survey form, which captures the user input as shown in diagram 24.18. On clicking the button 'Submit', the servlet i.e. Survey processes the data and returns a page, which displays the information entered in the form as shown diagram 24.19

Following is the source code of the HTML page i.e. Survey.html:

<HTML> <HEAD><TITLE> Customer Service </TITLE></HEAD> <BODY> <H1><CENTER> Survey Form </CENTER> <HR> <BR> <FORM Method=post Action="http://localhost:8080/examples/servlet/Survey"> <FONT Color="red"> <TABLE Border=0> <TR><TD Align="right"><B> Name: </B> </TD> <TD Colspan=2 Align="left"><INPUT Type="text" Name="name" Size=40></TD> </TR> <TR> <TD Align="right"> <B> Email Address: </B> </TD> <TD Colspan=2 Align="left"><INPUT Type="text" Name="email" Size=40></TD> </TR> <TR Valign="top"> <TD Align="right"><B> Age: </B> </TD> <TD Align="left"><INPUT Type="radio" Name="age" Value="<18"> Less than 18 <BR> <INPUT Type="radio" Name="age" value="18-25"> 18-25 <BR></TD> <TD Align="left"><INPUT Type="radio" Name="age" Value="26-40"> 26-40 <BR> <INPUT Type="radio" Name="age" Value=">40"> Over 40 <BR> </TD> </TR> <TR Valign="top"> <TD Align="right"> <B> Operating Systems: </B> </TD> <TD Align="left"><SELECT Name="os" Size=5 MULTIPLE> <OPTION> Win/95 <OPTION> NT <OPTION> Solaris <OPTION> HP-UX <OPTION> Other </SELECT> </TD> </TR> <TR><TD></TD> <TD><INPUT Type="checkbox" Name="more" Value="yes"> <FONT Color="red"> <U> Send me more information </U> </FONT> </TD> </TR> <TR> <TD Align="right"> <B> Comments: </B> </TD> <TD Colspan=2 Align="left"><TEXTAREA Name="comments" cols=40 rows=4>< /TEXTAREA></TD> </TR> <TR><TD></TD> <TD><INPUT Type="reset" Value="Clear Form"> <INPUT Type="Submit" Value="Submit"> </TD> </TR> </TABLE> </FORM> </BODY> </HTML>

Diagram 24.18 Output of Survey.html

The following is the source code for Survey.class

/*
===========================================================
File Name : Survey.java
WebSite : http://javaproglang.blogspot.in/
Facebook : https://www.facebook.com/AdvanceJavaProgramming
Twitter ID : https://twitter.com/AdvanceJava
Created By : Bintu Chaudhary
===========================================================
*/
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

/*
  * This is a simple servlet that will echo survey information
  * that was entered into an HTML form.
*/

public class Survey extends HttpServlet
{
	public void doPost(HttpServletRequest reqst, HttpServletResponse respn)
		throws ServletException, IOException
	{
		String name, email, age, more, comments;

		PrintWriter out;

		// Set  the content type of the reaponse 
		respn.setContentType("text/html");

		// Create a PrintWriter  to write the response
		out = new PrintWriter(respn.getOutputStream());

		// Print a standard header
		out.println("<HTML>");
		out.println("<HEAD>");
		out.println("<TITLE> Survey Complete </TITLE>");
		out.println("</HEAD>");

		// Get the name
		name = reqst.getParameter("name");

		// Get the email address
		email = reqst.getParameter("email");

		// Get the age
		age = reqst.getParameter("age");

		// Get the operating system
		String values[] = reqst.getParameterValues("os");

		// Get the 'more information' flag
		more = reqst.getParameter("more");

		// Get the comments
		comments = reqst.getParameter("comments");

		out.println("<BODY>");
		out.println("<H1> <CENTER>");
		out.println("<FONT Color=\"Blue\"> <U> Congratulation " + name + "!! </U> </FONT> <BR>");
		out.println("Your survey has been processed sucessfully!");
		out.println("</CENTER> </H1>");
		out.println("<HR> <BR>");
		
		out.println("<TABLE Border=0>");
			out.println("<TR> <TD Align=\"right\"> <B> Name: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">     " + name + "</TD> </TR>");

			out.println("<TR> <TD Align=\"right\"> <B> Email: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">     " + email + "</TD> </TR>");

			out.println("<TR> <TD Align=\"right\"> <B> Age: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">     " + age + "</TD> </TR>");

			out.println("<TR Valign=\"top\"> <TD Align=\"right\"> <B> Operating System: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">");

			// There could be more than one value in the Operating System selected
			if (values != null)
			{
				for (int i=0; i < values.length; i++)
				{
					if (i > 0)
						out.print("<BR>");

					out.print("    " + values[i]);
				}
			}
			out.println("</TD> </TR>");

			out.println("<TR> <TD Align=\"right\"> <B> More information: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">     " + more + "</TD> </TR>");

			out.println("<BR> <BR>");

			out.println("<TR> <TD Align=\"right\"> <B> Comments: </B> </TD>");
			out.println("<TD Colspan=2 Align=\"left\">     ");
				out.println(comments);
			out.println("</TD> </TR>");

		out.println("</TABLE>");

		// Wrap up
		out.println("</BODY>");
		out.println("</HTML>");
		out.flush();
	}
}

Diagram 24.19 Output of Survey.class

Java Servlet Programming

Creating Java Servlets (Compiling and Running a Java Servlet)

Generic and Http Servlets

Calling a servlet from within an HTML page

Using JDBC In Servlet

User Authentication Form using Java Servlet

2 comments:

AnonymousDecember 1, 2019 at 8:36 PM
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Calling a servlet from within an HTML page

Java Servlet Programming

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