Deleting Rows From Table
Consider a situation where we have entered some wrong
data and in later situation it starts giving problem to the organization. Rather
than go through with that data its better to delete that data. We can do it very
easily through our program, what we need is a simple query.
In this example we are going to exactly the same as we
said above. To make this possible we need to make a class named ServletDeletingRowsFromTable,
the name of the program should be such, if in future there is any need to
make any change in the program, you can easily understand in which program you
have to make a change. As we know that in Servlet the main logic of the
program is written inside the service method and in turn the service
method calls the doGet() method. Now inside the doGet() method use
the getWriter() method of the response object and its returns the PrintWriter
object, which helps us to write on the browser. To delete the unwanted data from
our table there is a need for the connection between the database and the java
program. After the establishment of the connection with the database, fire
a query for deleting the unwanted row in the database table. This query will be
fired inside the prepareStatement() method of the Connection
object and returns the PreparedStatement object. If the rows has been
deleted from the database table then print the message "row is
deleted" otherwise "no rows has been deleted".
The code of the program is given below:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class ServletDeletingRowsFromTable extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException{
int rows;
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
String connectionURL = "jdbc:mysql://localhost/zulfiqar";
Connection connection;
try{
Class.forName("org.gjt.mm.mysql.Driver");
connection = DriverManager.getConnection(connectionURL, "root", "admin");
PreparedStatement pst = connection.prepareStatement
("delete from emp_sal where EmpName = 'vinod'");
int i = pst.executeUpdate();
if (i==0){
pw.println("Row has been deleted");
}
else{
pw.println("No rows has been deleted");
}
}
catch(Exception e){
pw.println("The exception is " + e);
}
}
}
|
web.xml file for this program:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<servlet>
<servlet-name>Zulfiqar</servlet-name>
<servlet-class>ServletDeletingRowsFromTable</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Zulfiqar</servlet-name>
<url-pattern>/ServletDeletingRowsFromTable</url-pattern>
</servlet-mapping>
</web-app>
|
Table in the database before deletion:
mysql> select * from emp_sal;
+----------+--------+
| EmpName | salary |
+----------+--------+
| zulfiqar | 15000 |
| vinod | 12000 |
+----------+--------+
2 rows in set (0.00 sec) |
The output of the program is given below:
Table in the database after deletion:
mysql> select * from emp_sal;
+----------+--------+
| EmpName | salary |
+----------+--------+
| zulfiqar | 15000 |
+----------+--------+
1 row in set (0.05 sec) |
Download this
example
|
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