Welcome To The World Of Java

This site will teach you the basics of Java. It is not necessary to have any prior programming experience.

Product database:
create table Product
(
pid number (4),
pname varchar2 (15),
price number (6, 2)
);

web.xml:
<web-app>
<servlet>
<servlet-name>abc</servlet-name>
<servlet-class>DatabaServ</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>abc</servlet-name>
<url-pattern>/getdata</url-pattern>
</servlet-mapping>
</web-app>

DarabaServ.java:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class DatabaServ extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  String pid1 = req.getParameter("prodata_pid");
  String pname = req.getParameter("prodata_pname");
  String price1 = req.getParameter("prodata_price");
  int pid = Integer.parseInt(pid1);
  float price = Float.parseFloat(price1);
  try {
   DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
   Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:
    Hanuman ","
    scott ","
    tiger ");
    PreparedStatement ps = con.prepareStatement("insert into Product values (?,?,?)"); ps.setInt(1, pid); ps.setString(2, pname); ps.setFloat(3, price); int i = ps.executeUpdate(); pw.println("<h4>" + i + " ROWS INSERTED..."); con.close();
   } catch (Exception e) {
    res.sendError(503, "PROBLEM IN DATABASE...");
   }
  }
  public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
   doGet(req, res);
  }
 }
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class DataServ extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  String name = req.getParameter("persdata_eurn");
  String cname = req.getParameter("persdata_eurc");
  pw.println("<center><h3>HELLO..! Mr/Mrs. " + name + "</h3></center>");
  pw.println("<center><h3>Your COURSE is " + cname + "</h3></center>");
 }
 public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  doGet(req, res);
 }

web.xml:
<web-app>
<servlet>
<servlet-name>abc</servlet-name>
<servlet-class>DataServ</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>abc</servlet-name>
<url-pattern>/getdata</url-pattern>
</servlet-mapping>
</web-app>

NOTE:
1. Whenever we are not entering the data in html form that data will be treated as empty space.
2. Query string represents the data which is passed by client to the servlet through html form. URI stands for Uniform Resource Indicator which gives the location of servlet where it is available. URL stands for Uniform Resource Locator which gives at which port number, in which server a particular JSP or servlet is running. ht represents a context path which can be either a document root or a war file.
web.xml:

<web-app>
<context-param>
<param-name>v1</param-name>
<param-value>10</param-value>
</context-param>
<context-param>
<param-name>v2</param-name>
<param-value>20</param-value>
</context-param>
<servlet>
<servlet-name>abc</servlet-name>
<servlet-class>Serv1</servlet-class>
<init-param>
<param-name>v3</param-name>
<param-value>30</param-value>
</init-param>
</servlet>
<servlet>
<servlet-name>pqr</servlet-name>
<servlet-class>Serv2</servlet-class>
<init-param>
<param-name>v4</param-name>
<param-value>40</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>abc</servlet-name>
<url-pattern>/firstserv</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>pqr</servlet-name>
<url-pattern>/secondserv</url-pattern>
</servlet-mapping>
</web-app>

Serv1.java:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class Serv1 extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  ServletConfig config = getServletConfig();
  ServletContext ctx = config.getServletContext();
  String val1 = ctx.getInitParameter("v1");
  String val2 = ctx.getInitParameter("v2");
  String val3 = config.getInitParameter("v3");
  String val4 = config.getInitParameter("v4");
  int sum = Integer.parseInt(val1) + Integer.parseInt(val2);
  pw.println("<h3> Value of v1 is " + val1 + "</h3>");
  pw.println("<h3> Value of v2 is " + val2 + "</h3>");
  pw.println("<h3> Value of v3 is " + val3 + "</h3>");
  pw.println("<h3> Value of v4 is " + val4 + "</h3>");
  pw.println("<h2> Sum = " + sum + "</h2>");
 }
}


Serv2.java:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class Serv2 extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  ServletContext ctx = getServletContext();
  Enumeration en = ctx.getInitParameterNames();
  while (en.hasMoreElements()) {
   Object obj = en.nextElement();
   String cpname = (String) obj;
   String cpvalue = ctx.getInitParameter(cpname);
   pw.println("</h2>" + cpvalue + " is the value of " + cpname + "</h2>");
  }
 }
}


import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
public class DbServ extends HttpServlet {
 ServletConfig sc = null;
 public void init(ServletConfig sc) throws ServletException {
  super.init(sc);
  this.sc = sc;
 }
 public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  String dname = sc.getInitParameter("dname");
  String url = sc.getInitParameter("url");
  String tab = sc.getInitParameter("tab");
  try {
   Class.forName(dname);
   Connection con = DriverManager.getConnection(url, "scott", "tiger");
   Statement st = con.createStatement();
   ResultSet rs = st.executeQuery("select * from " + tab);
   while (rs.next()) {
    pw.println("<h2>" + rs.getString(1) + "" + rs.getString(2) + "" + rs.getString(3) + "</h2>");
   }
   con.close();
  } catch (Exception e) {
   res.sendError(503, "PROBLEM IN DATABASE...");
  }
 }
}



web.xml:

<web-app>
<servlet>
<servlet-name>abc</servlet-name>
<servlet-class>DbServ</servlet-class>
<init-param>
<param-name>dname</param-name>
<param-value>oracle.jdbc.driver.OracleDriver ()</param-value>
</init-param>
<init-param>
<param-name>url</param-name>
<param-value>jdbc:oracle:thin:@localhost:1521:Hanuman</param-value>
</init-param>
<init-param>
<param-name>tab</param-name>
<param-value>emp</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>abc</servlet-name>
<url-pattern>/dbdata</url-pattern>
</servlet-mapping>
</web-app>
package ddrs;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
public class RetrieveDataBaseServ extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  try {
   DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
   Connection con = DriverManager.getConnection("oracle:jdbc:thin:@localhost:1521:Hanuman ", "scott ","tiger ");
    Statement st = con.createStatement(); ResultSet rs = st.executeQuery("select * from emp");
    while (rs.next()) {
     pw.println(rs.getString(1) + " " + rs.getString(2));
    }
   } catch (Exception e) {
    res.sendError(504, "PROBLEM IN SERVLET...");
   }
  }
 }



<web-app>
<servlet>
<servlet-name>Babu</servlet-name>
<serclet-class>ddrs.RetrieveDataBaseServ</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Babu</servlet-name>
<url-pattern>Dinesh</url-pattern>
</servlet-mapping>
</web-app>
package ddrs;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
public class RetrieveDataBaseServ extends HttpServlet {
 public void doGet(HttpServletRequest req, HttpServletResponse res) {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  try {
   DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
   Connection con = DriverManager.getConnection("oracle:jdbc:thin:@localhost:1521: Hanuman " , "scott " , "tiger ");
    Statement st = con.createStatement(); ResultSet rs = st.executeQuery("select * from emp");
    while (rs.next()) {
     pw.println(rs.getString(1) + " " + rs.getString(2));
    }
   } catch (Exception e) {
    res.sendError(504, "PROBLEM IN SERVLET...");
   }
  }
 }


web.xml:

<web-app>
<servlet>
<servlet-name>Babu</servlet-name>
<serclet-class>ddrs.RetrieveDataBaseServ</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Babu</servlet-name>
<url-pattern>Dinesh</url-pattern>
</servlet-mapping>
</web-app>
package ds;
import javax.servlet.*;
import java.io.*;
import java.util.*;
public class DateServ extends GenericServlet {
 public DateServ() {
  System.out.println("SERVLET LOADED...");
 }
 public void init() {
  System.out.println("I AM FROM init METHOD...");
 }
 public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
  res.setContentType("text/html");
  PrintWriter pw = res.getWriter();
  Date d = new Date();
  String s = d.toString();
  pw.println("<h1> WELCOME TO SERVLETS <h1>");
  pw.println("<h2> CURRENT DATE & TIME IS : " + s + "<h2>");
 }
 public void destroy() {
  System.out.println("I AM FROM destroy METHOD...");
 }
} 



web.xml:

<web-app>
 <servlet>
   <servlet-name>kalyan</servlet-name>
   <servlet-class>ds.DateServ</servlet-class>
 </servlet>
 <servlet-mapping>
   <servlet-name>kalyan</servlet-name>
   <url-pattern>/suman</url-pattern>
 </servlet-mapping>
</web-app>
import javax.servlet.*;
import java.io.*;
public class First extends GenericServlet {
 public First() {
  System.out.println("I AM FROM DEFAULT CONSTRUCTOR...");
 }
 public void init() {
  System.out.println("I AM FROM init METHOD...");
 }
 public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
  System.out.println("I LOVE MY MOM...");
  System.out.println("I AM FROM service METHOD...");
 }
 public void destroy() {
  System.out.println("I AM FROM destroy METHOD...");
 }
}