A simple web application showing how to query a table in a database i.e performing a delete query using JDBC
Steps for querying a Database using JDBC -
1. Download the driver jar from Internet and place it in WEB-INF/lib folder of your Web application. Here I am using MySql as Database so I have downloaded the jar with name as : "mysql-connector-java-5.1.20-bin.jar"
2. Create a Database (am using MySql as backend) name as "javaee".
3. Create a table in "javaee" database as "customer". Run the create query stated below -
CREATE TABLE customer (
'First Name' varchar(30) ,
'Last Name' varchar(30) ,
'E-Mail' varchar(45) ,
'City' varchar(30) ,
'password' varchar(30) NOT NULL,
PRIMARY KEY ('password')
)
4. Populate the table user with some data (of your own), if not run the four insert queries stated below -
insert into customer () values ('Jonty','Magic','jonty@magic.com','Pune','123456');
insert into customer () values ('Java','Sun','java@sun.com','New York','456');
insert into customer () values ('Jesse','lool','jesse@lool.com','Jamaica','23456');
insert into customer () values ('Cameroon','Black','cameroon@black.com','Sydney','34');
5. Create a Servlet. It will perform necessary update query. The code for servlet is shown below -
package com.hubberspot.jdbc;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/DeleteJdbcQueryServlet")
public class DeleteJdbcQueryServlet extends HttpServlet {
Connection connection = null;
ResultSet resultSet = null;
Statement statement = null;
static String query = null;
String url = null;
String username = null;
String password = null;
public void init(ServletConfig config) throws ServletException {
url = "jdbc:mysql://localhost:3306/javaee";
username = "root";
password = "root";
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(url, username , password);
}
catch (Exception e) {
e.printStackTrace();
}
}
protected void doGet(
HttpServletRequest request,
HttpServletResponse response
) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(
HttpServletRequest request,
HttpServletResponse response
) throws ServletException, IOException {
query = "delete from customer where First_Name='Jonty';";
executeQuery(query);
query = "delete from customer where First_Name='Java';";
executeQuery(query);
}
private void executeQuery(String query) {
try {
statement = connection.createStatement();
statement.execute(query);
}
catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void destroy() {
try {
statement.close();
connection.close();
}
catch (SQLException e) {
e.printStackTrace();
}
}
}
Output after Insert query -
Output after Delete query -
