Watch “Servlet Part 21 | CRUD operation in Servlet Using JDBC (Gujarati)” on YouTube

#CRUD #Servlet #JDBC #MySql #Eclipse #MySqlWorkbench #ApacheTomcat #Jdk #Java

This video features the CRUD operation using JDBC via servlet only, no JSP page is used to perform any database operation.
CRUD is Create, Read, Update & Delete.

Index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Servlet with JDBC</title>
</head>
<body>
<form action="AddEmp" method="post">
<h1> Employee Management</h1>
<p> Enter Emp. No : <input type="text" name="txtEno"> </p>
<p> Enter Emp. Name : <input type="text" name="txtEname"> </p>
<p> Enter Emp. Salary : <input type="text" name="txtEsalary"> </p>

<p> DB Operation :
<select name="op">
    <option value="1">Add</option>
    <option value="2">Update</option>
    <option value="3">Delete</option>
    <option value="4">Display</option>
</select>
</p>

<p> <input type="submit" value="Submit"> </p>
</form>
</body>
</html>

AddEmp.java

package servletWithJDBC;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;

@WebServlet("/AddEmp")
public class AddEmp extends HttpServlet 
{
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
	{			
		response.setContentType("text/html");
		PrintWriter pw = response.getWriter();
		String op = request.getParameter("op");
		Connection conn;
		PreparedStatement pst=null; 
		String url,username,password,qry="";
		url = "jdbc:mysql://localhost:3306/raviroza";
		username="root";
		password="ravi";	
		
		int eno;
		String ename="";
		float esalary;
		try 
		{
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(url,username,password);			
			
			if(op.equals("1"))
			{
				eno = Integer.parseInt(request.getParameter("txtEno"));
				ename = request.getParameter("txtEname");
				esalary = Float.parseFloat(request.getParameter("txtEsalary"));
				
				qry = "insert into emp values (?,?,?)";
				pst = conn.prepareStatement(qry);
				pst.setInt(1, eno);
				pst.setString(2, ename);
				pst.setFloat(3, esalary);
				pst.executeUpdate();
			}
			else if(op.equals("2"))
			{
				eno = Integer.parseInt(request.getParameter("txtEno"));
				ename = request.getParameter("txtEname");
				esalary = Float.parseFloat(request.getParameter("txtEsalary"));
				
				qry = "update emp set ename=?,esalary=? where eno=?";
				pst = conn.prepareStatement(qry);				
				pst.setString(1, ename);
				pst.setFloat(2, esalary);
				pst.setInt(3, eno);
				pst.executeUpdate();
			}
			else if(op.equals("3"))
			{
				eno = Integer.parseInt(request.getParameter("txtEno"));
				qry = "delete from emp where eno=?";	
				pst = conn.prepareStatement(qry);								
				pst.setInt(1, eno);
				pst.executeUpdate();
			}								
						
			qry = "select * From Emp Order by eno desc";
			ResultSet rs = conn.prepareStatement(qry).executeQuery();
			pw.println("<table border=1>");
			pw.println("<th>Eno.</th>");
			pw.println("<th>Emp. Name</th>");
			pw.println("<th>Emp. Salary</th>");
			while(rs.next())
			{
				pw.println("<tr>");
				pw.println("<td>"+rs.getString("eno")+"</td>");
				pw.println("<td>"+rs.getString("ename")+"</td>");
				pw.println("<td>"+rs.getString("esalary")+"</td>");
				pw.println("</tr>");
			}
						
			pw.println("<h2> Employee Info. updated Successfully ! </h2>");
			pw.println("<a href='index.html'>Back</a>");
			
			pw.close();
			pst.close();
			conn.close();		
		}
		catch (ClassNotFoundException | SQLException e) 
		{
			pw.println("<h2> Driver|SQL Error "+e.toString() +"</h2>");
		}
	}
}

Overall process of example.

It is generally the table operation to create, access, manipulate, and delete the data from a database table.
Here, only a single Servlet is performing all the CRUD operation. Operation is decided by the client by selecting a proper option from list of choices.

When a client/user select the “Add” option, the internal value of that option is checked to perform the add operation, like wise when user/client select the “Update” operation the record is updated with given details.

If user/client decide to delete the record the valid number is given and the delete operation is carried.

Finally, if user decides to display all the record there is an option called “Display” to view all the details of the table.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Database : MySQL using MySql Workbench 5.2 CE
Server : Apache Tomcat 7

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Watch “Servlet Part-16 | How to use Cookies in Servlet (Gujarati)” on YouTube

Video features introduction to Session management.
To track the user session various session tracking approaches are there in servlet.
Here, the Cookies is discussed with suitable example. Index page is used to read user’s name from the client, at the server side there are three servlets. First servlet receives the input/request from the index page, then the session information added using Cookies, then the second servlet also adds the session information in the second servlet using Cookies, and finally third servlet gets the client session information from second servlet.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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Watch “Servlet Part-13 (Single Thread Model)” on YouTube

Single Thread Model:
It was designed to guarantee that only one thread is executed at a time in a given servlet instance’s service method.
It should be implemented to ensure that servlet can handle only one request at a time.

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It is a marker interface and has no methods.
This interface is currently deprecated.
Once the interface is implemented the system guarantees that there’s never more than one request thread accessing a single instance of servlet.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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Watch “Servlet Part-12 (Servlet Collaboration)” on YouTube

Some times servlets have to cooperate, i.e. usually by sharing information.
This communication can be called as Sort Servlet collaboration.
The servlet, which are collaborating, can pass the shared information directly from one servlet to another. Request Dispatcher defines an object that receives requests from the client and sends them to any resource (such as a servlet, HTML file, or JSP file) on the server. The servlet container creates the RequestDispatcher object, which is used as a wrapper around a server resource located at a particular path or given by a particular name.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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Watch “Servlet Part-11 (Redirection in Servlet)” on YouTube

Servlet Redirection :

  • Local resource like servlet, jsp or html page etc.
  • Resource outside of our domain/application
  • Example of searching Google from out application

Servlet Redirection can be used to transfer/forward control to Local resource like servlet, jsp or html page etc., It can also used to transfer/forward the Resource outside of our domain/application. Here there is an example to transfer request from one servlet to anohter servlet when client request the first servlet. This example also demonstrate how it refers the another html page for redirection. And finally this example also demonstrate a trick to search Google directly from our application.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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Watch “Servlet Part-10 (Demo of Request Object Methods)” on YouTube

Demonstration of HttpRequest object methods, such as getRemoteAddr(), getRemoteHost(), getQueryString(), setAttribute(), getAttribute(), getAttributeNames(). To check all these method its is suggestible to create html/jsp page that will call/execute/request the servlet which will be using above methods.

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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Watch “Servlet Part-9 (Enumeration to Read Headers and Parameters)” on YouTube

A request object of servlet consist the client information , such as client header information and client input parameters.
Here, Enumeration is used to read the values of client headers (list of headers) and to read the values of parameters (list of input parameters).

OS : Windows 10
Jdk : Version 8
IDE : Eclipse Mars
Server : Apache Tomcat 7

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