web

9. Session Handling using cookies
index.html
<form method="post" action=" validate ">
Name:<input type="text" name="user" /><br/>
Password:<input type="text" name="pass" ><br/>
<input type="submit" value="submit">
</form>
web.xml
<webapp...>
<servlet>
<servletname>
validate </servletname>
<servletclass>
MyServlet </servletclass>
</servlet>
<servletmapping>
<servletname>
validate </servletname>
<urlpattern>/
validate</urlpattern>
</servletmapping>
<servlet>
<servletname>
First </servletname>
<servletclass>
First </servletclass>
</servlet>
<servletmapping>
<servletname>
First </servletname>
<urlpattern>/
First</urlpattern>
</servletmapping>
<welcomefilelist>
<welcomefile>
index.html </welcomefile>
</welcomefilelist>
</webapp>
MyServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
protected void doPost (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
String name = request.getParameter(" user ");
String pass = request.getParameter(" pass ");
if(pass. equals ("1234"))
{
Cookie ck = new Cookie(" username ", name );
response. addCookie ( ck );
response.sendRedirect(" First ");
}
}
}
First.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class First extends HttpServlet {
protected void doGet (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
Cookie[] cks = request.getCookies();
out.println("Welcome "+ cks[0].getValue() );
}
}
10.
Session Hndling using URL Rewriting
index.html
<form method="post" action=" validate ">
Name:<input type="text" name="user" /><br/>
Password:<input type="text" name="pass" ><br/>
<input type="submit" value="submit">
</form>
web.xml
<webapp...>
<servlet>
<servletname>
validate </servletname>
<servletclass>
MyServlet </servletclass>
</servlet>
<servletmapping>
<servletname>
validate </servletname>
<urlpattern>/
validate</urlpattern>
</servletmapping>
<servlet>
<servletname>
First </servletname>
<servletclass>
First </servletclass>
</servlet>
<servletmapping>
<servletname>
First </servletname>
<urlpattern>/
First</urlpattern>
</servletmapping>
<welcomefilelist>
<welcomefile>
index.html </welcomefile>
</welcomefilelist>
</webapp>
MyServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyServlet extends HttpServlet {
protected void doPost (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
String name = request.getParameter(" user ");
String pass = request.getParameter(" pass ");
if(pass. equals ("1234"))
{
response.sendRedirect( "First?user_name="+ name +"" );
}
}
}
First.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class First extends HttpServlet {
protected void doGet (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
String user = request.getParameter(" user_name ");
out.println("Welcome "+user);
}
}
11. Session management using hidden form fields :
index.html
<form method="post" action=" validate ">
Name:<input type="text" name="user" /><br/>
Password:<input type="text" name="pass" ><br/>
<input type="submit" value="submit">
</form>
web.xml
<webapp...>
<servlet>
<servletname>
First </servletname>
<servletclass>
First </servletclass>
</servlet>
<servletmapping>
<servletname>
First </servletname>
<urlpattern>/
First</urlpattern>
</servletmapping>
<servlet>
<servletname>
Second </servletname>
<servletclass>
Second </servletclass>
</servlet>
<servletmapping>
<servletname>
Second </servletname>
<urlpattern>/
Second</urlpattern>
</servletmapping>
<welcomefilelist>
<welcomefile>
index.html </welcomefile>
</welcomefilelist>
</webapp>
First.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class First extends HttpServlet {
protected void doPost (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
//getting value submitted in form from HTML file
String user = request.getParameter("user");
//creating a new hidden form field
out.println("<form action='Second'>");
out.println("<input type='hidden' name='user' value='"+ user +"'>");
out.println("<input type='submit' value='submit' >");
out.println("</form>");
}
}
Second.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Second extends HttpServlet {
protected void doGet (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
//getting parameter from the hidden field
String user = request.getParameter(" user ");
out.println("Welcome "+ user );
}
}
HTTP Session
12. http://www.studytonight.com/servlet/httpsession.php
index.html
<form method="post" action=" Validate ">
User: <input type="text" name="user" /><br/>
Password: <input type="text" name="pass" ><br/>
<input type="submit" value="submit">
</form>
web.xml
<webapp..>
<servlet>
<servletname>
Validate </servletname>
<servletclass>
Validate </servletclass>
</servlet>
<servlet>
<servletname>
Welcome </servletname>
<servletclass>
Welcome </servletclass>
</servlet>
<servletmapping>
<servletname>
Validate</servletname>
<urlpattern>/
Validate</urlpattern>
</servletmapping>
<servletmapping>
<servletname>
Welcome</servletname>
<urlpattern>/
Welcome</urlpattern>
</servletmapping>
<welcomefilelist>
<welcomefile>
index.html </welcomefile>
</welcomefilelist>
</webapp>
Validate.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Validate extends HttpServlet {
protected void doPost (HttpServletRequest request, HttpServletResponse
response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
String name = request.getParameter("user");
String pass = request.getParameter("pass");
if(pass. equals ("1234"))
{
//creating a session
HttpSession session = request.getSession();
session. setAttribute (" user ", name );
response. sendRedirect ("Welcome");
}
}
}
Welcome.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Welcome extends HttpServlet {
protected void doGet (HttpServletRequest request, HttpServletResponse
response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF8");
PrintWriter out = response.getWriter();
HttpSession session = request.getSession();
String user = (String)session.getAttribute(" user ");
out.println("Hello "+ user );
}
}
13. Servelet Collaboration REquest
dispatch
http://www.javatpoint.com/requestdispatcherinservlet
index.html
<form action= "servlet1" method= "post" >
Name:<input type= "text" name= "userName" /><br/>
Password:<input type= "password" name= "userPass" /><br/>
<input type= "submit" value= "login" />
</form>
Login.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Login extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType( "text/html" );
PrintWriter out = response.getWriter();
String n=request.getParameter( "userName" );
String p=request.getParameter( "userPass" );
if (p.equals( "servlet" ){
RequestDispatcher rd=request.getRequestDispatcher( "servlet2" );
rd.forward(request, response);
}
else {
out.print( "Sorry UserName or Password Error!" );
RequestDispatcher rd=request.getRequestDispatcher( "/index.html" );
rd.include(request, response);
}
}
}
WelcomeServlet.java
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class WelcomeServlet extends HttpServlet {
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType( "text/html" );
PrintWriter out = response.getWriter();
String n=request.getParameter( "userName" );
out.print( "Welcome " +n);
}
}
web.xml<webapp>
<servlet>
<servletname>
Login</servletname>
<servletclass
>Login</servletclass
>
</servlet>
<servlet>
<servletname>
WelcomeServlet</servletname>
<servletclass
>WelcomeServlet</servletclass
>
</servlet>
<servletmapping>
<servletname>
Login</servletname>
<urlpattern>/
servlet1</urlpattern>
</servletmapping>
<servletmapping>
<servletname>
WelcomeServlet</servletname>
<urlpattern>/
servlet2</urlpattern>
</servletmapping>
<welcomefilelist>
<welcomefile>
index.html</welcomefile>
</welcomefilelist>
</webapp>
14. Servlet Collab using Servlet context
15. Filterss
http://www.javatpoint.com/servletfilter
16. Jdbc for insert and extract details from a table
//STEP 1. Import required packages
import java . sql .*;
public class JDBCExample {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver" ;
static final String DB_URL = "jdbc:mysql://localhost/STUDENTS" ;
// Database credentials
static final String USER = "username" ;
static final String PASS = "password" ;
public static void main ( String [] args ) {
Connection conn = null ;
Statement stmt = null ;
try {
//STEP 2: Register JDBC driver
Class . forName ( "com.mysql.jdbc.Driver" );
//STEP 3: Open a connection
System . out . println ( "Connecting to a selected database..." );
conn = DriverManager . getConnection ( DB_URL , USER , PASS );
System . out . println ( "Connected database successfully..." );
//STEP 4: Execute a query
System . out . println ( "Creating statement..." );
stmt = conn . createStatement ();
String sql = "SELECT id, first, last, age FROM Registration" ;
ResultSet rs = stmt . executeQuery ( sql );
//STEP 5: Extract data from result set
while ( rs . next ()){
//Retrieve by column name
int id = rs . getInt ( "id" );
int age = rs . getInt ( "age" );
String first = rs . getString ( "first" );
String last = rs . getString ( "last" );
//Display values
System . out . print ( "ID: " + id );
System . out . print ( ", Age: " + age );
System . out . print ( ", First: " + first );
System . out . println ( ", Last: " + last );
}
rs . close ();
} catch ( SQLException se ){
//Handle errors for JDBC
se . printStackTrace ();
} catch ( Exception e ){
//Handle errors for Class.forName
e . printStackTrace ();
} finally {
//finally block used to close resources
try {
if ( stmt != null )
conn . close ();
} catch ( SQLException se ){
} // do nothing
try {
if ( conn != null )
conn . close ();
} catch ( SQLException se ){
se . printStackTrace ();
} //end finally try
} //end try
System . out . println ( "Goodbye!" );
} //end main
} //end JDBCExample
17. Servlet databse insert:
http://www.tutorialspoint.com/servlets/pdf/servletsdatabaseaccess.
pdf
// Loading required libraries
import java . io .*;
import java . util .*;
import javax . servlet .*;
import javax . servlet . http .*;
import java . sql .*;
public class DatabaseAccess extends HttpServlet {
public void doGet ( HttpServletRequest request ,
HttpServletResponse response )
throws ServletException , IOException
{
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver" ;
static final String DB_URL = "jdbc:mysql://localhost/TEST" ;
// Database credentials
static final String USER = "root" ;
static final String PASS = "password" ;
// Set response content type
response . setContentType ( "text/html" );
PrintWriter out = response . getWriter ();
String title = "Database Result" ;
String docType =
"<!doctype html public \"//
w3c//dtd html 4.0 " +
"transitional//en\">\n" ;
out . println ( docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n" +
"<body bgcolor=\"#f0f0f0\">\n" +
"<h1 align=\"center\">" + title + "</h1>\n" );
try {
// Register JDBC driver
Class . forName ( "com.mysql.jdbc.Driver" );
// Open a connection
Connection conn = DriverManager . getConnection ( DB_URL , USER , PASS );
// Execute SQL query
Statement stmt = conn . createStatement ();
String sql ;
sql = "SELECT id, first, last, age FROM Employees" ;
ResultSet rs = stmt . executeQuery ( sql );
// Extract data from result set
while ( rs . next ()){
//Retrieve by column name
int id = rs . getInt ( "id" );
int age = rs . getInt ( "age" );
String first = rs . getString ( "first" );
String last = rs . getString ( "last" );
//Display values
out . println ( "ID: " + id + "<br>" );
out . println ( ", Age: " + age + "<br>" );
out . println ( ", First: " + first + "<br>" );
out . println ( ", Last: " + last + "<br>" );
}
out . println ( "</body></html>" );
// Cleanup
environment
rs . close ();
stmt . close ();
conn . close ();
} catch ( SQLException se ){
//Handle errors for JDBC
se . printStackTrace ();
} catch ( Exception e ){
//Handle errors for Class.forName
e . printStackTrace ();
} finally {
//finally block used to close resources
try {
if ( stmt != null )
stmt . close ();
} catch ( SQLException se2 ){
} // nothing we can do
try {
if ( conn != null )
conn . close ();
} catch ( SQLException se ){
se . printStackTrace ();
} //end finally try
} //end try
}
}
Now let us compile above servlet and create following entries in web.xml
....
<servlet>
< servlet name
> DatabaseAccess </ servlet name
>
< servlet class
> DatabaseAccess </ servlet class
>
</ servlet >
< servlet mapping
>
< servlet name
> DatabaseAccess </ servlet name
>
< url pattern
> /DatabaseAccess</ url pattern
>
</ servlet mapping
>
O/P :
ID: 100, Age: 18, First: Zara, Last: Ali
ID: 101, Age: 25, First: Mahnaz, Last: Fatma
ID: 102, Age: 30, First: Zaid, Last: Khan
ID: 103, Age: 28, First: Sumit, Last: Mittal
18. HTML Form and retrieving inputs using jsp
What You'll Learn in This Hour:
● How to use a JSP to receive form data
● How to work with form parameters
● How servlets interact with forms
● How to use a single JSP to present a form and handle its submission
By now you are probably comfortable with the fundamentals of JavaServer Pages and servlets. In the
examples presented so far, you have learned how to send output back to the browser. One of the
advantages of the Web is that you can create forms to send data from the browser to the server. You are
finally ready to begin creating forms with JSP and servlets, and that's where the fun really begins!
A Simple HTML Form
To start off the exploration of HTML forms, it's best to start with a small form and expand from there. Also,
it's better to start with a JSP rather than a servlet, because it is easier to write out the HTML. Most of the
form handling for JSPs and servlets is identical, so after you know how to retrieve form information from a
JSP, you know how to do it from a servlet. Listing 3.1 shows an HTML file containing a simple input form
that calls a JSP to handle the form.
Listing 3.1 Source Code for SimpleForm.html
<html>
<body>
<h1>Please tell me about yourself</h1>
<form action="SimpleFormHandler.jsp" method="get">
Name: <input type="text" name="firstName">
<input type="text" name="lastName"><br>
Sex:
<input type="radio" checked name="sex" value="male">Male
<input type="radio" name="sex" value="female">Female
<p>
What Java primitive type best describes your personality:
<select name="javaType">
<option value="boolean">boolean</option>
<option value="byte">byte</option>
<option value="char" selected>char</option>
<option value="double">double</option>
<option value="float">float</option>
<option value="int">int</option>
<option value="long">long</option>
</select>
<br>
<input type="submit">
</form>
</body>
</html>
The <form> tag in Listing 3.1 sends the input from the form to a JSP called SimpleFormHandler.jsp . Figure
3.1 shows this form running in a browser.
Figure
3.1 HTML forms frequently serve as the front end for a JSP.
The SimpleFormHandler JSP does little more than retrieve the form variables and print out their values.
Listing 3.2 shows the contents of SimpleFormHandler.jsp , which you can see is pretty short.
Listing 3.2 Source Code for SimpleFormHandler.jsp
<html>
<body>
<%
// Grab the variables from the form.
String firstName = request.getParameter("firstName");
String lastName = request.getParameter("lastName");
String sex = request.getParameter("sex");
String javaType = request.getParameter("javaType");
%>
<%Print
out the variables. %>
<h1>Hello, <%=firstName%> <%=lastName%>!</h1>
I see that you are <%=sex%>. You know, you remind me of a
<%=javaType%> variable I once knew.
</body>
</html>
19. JSP Tags’
Tag handler class:
A tag handler class should implement Tag / IterationTag / BodyTag interface or it can
also extend TagSupport / BodyTagSupport / SimpleTagSupport class. All the classes
that support custom tags are present inside javax.servlet.jsp.tagext . In the below
we are extending the class SimpleTagSupport .
Details.java
package beginnersbook.com;
import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.*;
public class Details extends SimpleTagSupport {
public void doTag() throws JspException , IOException {
/*This is just to display a message, when
* we will use our custom tag. This message
* would be displayed
*/
JspWriter out = getJspContext().getOut();
out .println( "This is my own custom tag" );
}
}
TLD File
This file should present at the location: Project Name/WebContent/WEB‐INF/ and
it should have a .tld extension.
Note:
<name> tag: custom tag name. In this example we have given it as MyMsg
<tag‐class> tag: Fully qualified class name. Our tag handler class Details.java is in
package beginnersbook.com so we have given the value as
beginnersbook.com.Details .
message.tld
<taglib>
<tlibversion>
1.0 </tlibversion>
<jspversion>
2.0 </jspversion>
<shortname>
My Custom Tag </shortname>
<tag>
<name> MyMsg </name>
<tagclass>
beginnersbook.com.Details </tagclass>
<bodycontent>
empty </bodycontent>
</tag>
</taglib>
Using custom tag in JSP:
Above we have created a custom tag named MyMsg . Here we will be using it.
Note: taglib directive should have the TLD file path in uri field. Above we have
created the message.tld file so we have given the path of that file.
Choose any prefix and specify it in taglib directive’s prefix field. Here we have
specified it as myprefix .
Custom tag is called like this: <prefix:tagName/> . Our prefix is myprefix and tag
name is MyMsg so we have called it as <myprefix:MyMsg/> in the below JSP page.
<%@ taglib prefix= "myprefix" uri= "WEBINF/
message.tld" %>
<html>
<head>
<title> Custom Tags in JSP Example </title>
</head>
<body>
<myprefix:MyMsg/>
</body>
</html>
Output:
This is my own custom tag