In this tutorial you will learn how to use elt() String function of mysql with java servlet
Mysql ELT() Function Example Using Java Servlet
In this tutorial you will learn how to use elt() String function of mysql with java servlet
ELT() method of mysql returns the value at the specified index position given as, the first argument in the parameter of this function. In this function if the index value is specified less than 1 or greater than the number of strings given into the parameter, returns null.
Syntax :
elt(index number,'string1','string2'...,'stringN');
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlEltServlet which extends the HttpServlet class. In the body of class I overridden the method doGet() and created an objects of HttpServletRequest and HttpServletResponse into its parameter. Inside the doGet() method first I set the mime type that in which format the browser will show the output. In the next line I used the getWriter() method of ServletResponse interface with the object of HttpServletResponse. HttpServletResponse interface extends this method from the ServletResponse. In Next step I am taking inputs using the getParameter() method of ServletRequest with the object of HttpServletRequest. In continue we have to establish a connection between java code and database system. So, since I am using Mysql in the example given below therefore, I am loading the driver of mysql and make a connection by using the getConnection() method of DriverManager class. It returns a Connection. Further I am passing the query "SELECT ELT("+i+","+"'"+str+"'"+","+"'"+str1+"'"+","+"'"+str2+"'"+")"; (This query will return the output as value of the specified index position. Here i, str, str1, str2 are the variables that stores the value given by the user.) into the parameter of prepareStatement() method of Connection interface which gives an object of PreparedStatement interface. In the next line I used the executeQuery() method of PreparedStatement interface which returns a ResultSet object that holds the result of query. At last I have extracted the result from the ResultSet object.
Example :
Elt.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Elt Function</title> </head> <body> <form method="get" action="MysqlEltServlet"> <table> <tr> <td>Enter a number for index</td> <td><input type="text" name="txtName"/></td> </tr> <tr> <td>Enter string</td> <td><input type="text" name="txtName1"/></td> </tr> <tr> <td>Enter string</td> <td><input type="text" name="txtName2"/></td> </tr> <tr> <td>Enter string</td> <td><input type="text" name="txtName3"/></td> </tr> <tr> <td align="center"><input type="submit" value="CLICK"/></td> </tr> </table> </form> </body> </html>
MysqlEltServlet.java
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MysqlEltServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
int i=(Integer.parseInt(request.getParameter("txtName")));
String str=request.getParameter("txtName1");
String str1=request.getParameter("txtName2");
String str2=request.getParameter("txtName3");
String className="com.mysql.jdbc.Driver";
String url="jdbc:mysql://192.168.10.13";
String user="root";
String password="root";
Connection con;
PreparedStatement ps;
ResultSet rs;
try
{
Class.forName(className);
con=DriverManager.getConnection(url, user, password);
String sql = "SELECT ELT("+i+","+"'"+str+"'"+","+"'"+str1+"'"+","+"'"+str2+"'"+")";
ps=con.prepareStatement(sql);
rs=ps.executeQuery();
while(rs.next())
{
sql=rs.getString(1);
out.println("Value at the index "+i+" is = "+"\""+sql+"\"");
}
}
catch(SQLException sx)
{
out.println(sx);
}
catch(ClassNotFoundException cx)
{
out.println(cx);
}
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>mysqlStringFunction</display-name> <servlet> <servlet-name>MysqlEltServlet</servlet-name> <servlet-class>MysqlEltServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlEltServlet</servlet-name> <url-pattern>/MysqlEltServlet</url-pattern> </servlet-mapping> </web-app>
Output
When you will execute the above example you will get the output as :
1.
2. When you will enter the value.
3. Output when you will click on CLICK button.
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