Retrieving Data from the table using Statement
In this program we are going to fetch the data from the
database in the table from our java program.
To accomplish our goal we first have to make a class
named as ServletFetchingData which must extends the abstract HttpServlet
class, the name of the class should be such that the other person can understand
what this program is going to perform. The logic of the program will be written
inside the doGet() method which takes two arguments, first is HttpServletRequest
interface and the second one is the HttpServletResponse interface
and this method can throw ServletException.
Inside this method call the getWriter() method
of the PrintWriter class. We can retrieve the data from the database only
and only if there is a connectivity between our database and the java program.
To establish the connection between our database and the java program we firstly
need to call the method forName() which is static in nature of the class ClassLoader.
It takes one argument which tells about the database driver we are going
to use. Now use the static method getConnection() of the DriverManager
class. This method takes three arguments and returns the Connection
object. SQL statements are executed and results are returned within the
context of a connection. Now your connection has been established. Now use the
method createStatement() of the Connection object which will
return the Statement object. This object is used for executing a static
SQL statement and obtaining the results produced by it. As we need to retrieve
the data from the table so we need to write a query to select all the records
from the table. This query will be passed in the executeQuery() method of
Statement object, which returns the ResultSet object. Now the data
will be retrieved by using the getString() method of the ResultSet
object.
The code of the program is given below:
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ServletFetchingDataFromDatabase1 extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException{
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
String connectionURL = "jdbc:mysql://localhost/zulfiqar";
Connection connection=null;
try{
Class.forName("org.gjt.mm.mysql.Driver");
connection = DriverManager.getConnection(connectionURL, "root", "admin");
Statement st = connection.createStatement();
ResultSet rs = st.executeQuery("Select * from emp_sal");
while(rs.next()){
pw.println("EmpName" + " " + "EmpSalary" + "<br>");
pw.println(rs.getString(1) + " " + rs.getString(2) + "<br>");
}
}
catch (Exception e){
pw.println(e);
}
}
}
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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>Hello</servlet-name>
<servlet-class>ServletFetchingDataFromDatabase</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/ServletFetchingDataFromDatabase</url-pattern>
</servlet-mapping>
</web-app>
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The output of the program is given below:
Table in the database:
mysql> select * from emp_sal;
+----------+--------+
| EmpName | salary |
+----------+--------+
| zulfiqar | 15000 |
| vinod | 12000 |
+----------+--------+
2 rows in set (0.00 sec) |
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