What now?
Both JSP and servlets combined together forms a better web application. Lets write a sample application that involves both JSP and Servlets.we will use four files for this example.
- home.jsp
- AuthenticateServlet.java
- welcome.jsp
- error.jsp
Examples
index.jsp
This is like our login page where the user will enter an username and password.<HTML> <BODY> <h5>Welcome to VikiMail !</h5> <h4>Login</h4> <FORM ACTION = "AuthenticateUser" METHOD ="POST"> Username: <INPUT TYPE = "TEXT" NAME = "username"> Password: <INPUT TYPE = "PASSWORD" NAME = "password"> <INPUT TYPE = "SUBMIT" VALUE = "Login"> </FORM> </BODY> </HTML>
AuthenticateServlet.java
This is the only servlet program in our example. It will be invoked when we enter username/password and submit the index.jsp page.For making it simple, this servlet just checks if the password is super*, goes to success.jsp. Otherwise it will go to error.jsp
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class AuthenticateServlet extends HttpServlet
{
public void doPost
(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
String username = request.getParameter("username").toString();
String password = request.getParameter("password").toString();
if(password.equals("super*"))
response.sendRedirect("success.jsp");
else
response.sendRedirect("error.jsp");
}
}
web.xml
This file, usually resides inside the WEB-INF folder. Whatever servlets we have written in our application, we need to specify it here.In our case there is one servlet called AuthenticateServlet.java.
Mapping with web.xml
Follow these steps to add a servlet mapping.1) Create a <servlet> </servlet> tag.
2) Create a <servlet-name> tag and <servlet-class> tag INSIDE the <servlet> tag like shown below.
<servlet> <servlet-name> </servlet-name> <servlet-class> </servlet-class> </servlet>3) In <servlet-class>, give the .class name of the servlet program. The name you specify here must be the same name as the servlet program file name.
4) In </servlet-name> tag, give any dummy name. This is like a reference name for mapping purposes. The dummy name given here needs be specified exactly in another place of the web.xml file.
<servlet> <servlet-name>CallAuthenticate</servlet-name> <servlet-class>AuthenticateServlet</servlet-class> </servlet>5) Create a <servlet-mapping> tag and inside that, create two other tags namely, <servlet-name> and <url-pattern> like the one which is shown below.
<servlet-mapping> <servlet-name> </servlet-name> <url-pattern> </url-pattern> </servlet-mapping>6) In the <servlet-name> tag (under <servlet-mapping>), give the same dummy name that you specified in the <servlet-name> tag under <servlet> tag.
7) Finally in the <url-pattern> tag, give this symbol first. : /
8) Followed by the slash, give any URL name.
Remember: This URL pattern will be specified in the ACTION attribute of the <form> tag in the jsp page. (Check the index.jsp page)
After changing everything, your web.xml will look something like this.
Note: Follow the same procedure for creating servlet mappings. Except for the (1)Actual java file name (2) dummy servlet name and the (3) URL Pattern, everything procedure remains same.
web.xml
<?xml version="1.0"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> <display-name>Demo Application</display-name> <description> For Learning purposes. </description> <servlet> <servlet-name>CallAuthenticate</servlet-name> <servlet-class>AuthenticateServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CallAuthenticate</servlet-name> <url-pattern>/AuthenticateUser</url-pattern> </servlet-mapping> </web-app>
success.jsp
This is the page that the servlet re-directs to when the password is correct.<HTML> <h5>Welcome!</h5><BR> <h4>Login Successful</h4> </HTML>
error.jsp
This is the page that the servlet re-directs to when the password is wrong.<HTML> <h5>Sorry!</h5><BR> <h4>Login failed</h4> </HTML>
good work man.... all the best.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteHow to communicate java socket application using JSP for web apps?
ReplyDelete@Brad: Interesting question you have asked there. Java is a wonderful language which almost provided anything a programmer wanted.
ReplyDeleteIt gave options to write and read from Sockets.
It gave options to write console based apps.
It gave options to build GUI based Desktop applications using AWT and Applet..
It then gave this J2EE extension which enabled us to write client server programs and web-based applications.
One interesting feature among all these is that we can put a socket program straight into a JSP.
JSP can run ANY Java program.
A Java program can communicate with Sockets.
So, JSP can communicate to sockets.
Note: Although using JSP to connect to sockets is possible, it's not the right practice. JSP are supposed to be used to PRESENT CONTENT to the USER. To do this Socket commmunication and things, you can use Servlets, which are meant exactly for this purpose: Back-end operations.
How to learn jsp, jdbc, servlets for an interview in 2 days? New to java but want to learn above technologies?
ReplyDelete@Fico:
ReplyDeleteThis is like reading and understanding The Bible in 2 days, which is not possible. I suggest You try and better your understanding of the core concepts by extensively reading random internet articles on these topics!
-Vignesh
Terrific example here. I found it very straightforward, especially compared to everything else out there. The accompanying video is very helpful as well. Thanks much to the author(s)!
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ReplyDeleteIs Using JSP pages with Oracle databse a good approach to develop well structed and secure web applications?
ReplyDeleteThanks for such an informative blog post, you helped me a lot in learning many important aspects. keep guiding.
ReplyDeleteMy apache server didn't start,how to rectify this problem? pls help sir.
ReplyDeleteHow to compare the 2 user input strings in jsp sir......
ReplyDelete