In this tutorial you will learn how to use mid() String function of mysql with java servlet
Mysql MID() Function Example Using Java Servlet
In this tutorial you will learn how to use mid() String function of mysql with java servlet
When a MID() function of mysql is called it returns a string this returned value is depends upon the arguments of this function. The first argument is a string from which a substring is to extracted, the second argument is an index position that specifies at which position the substring has to be extracted, and the third argument is a length which specifies the number of characters of substring you want to extract from the string.
Syntax :
mid('string', ind_pos,len);
Here the argument "string", is a string from which a substring will be extracted, "ind_pos" specifies the position of string at which a substring will start to extract, and "len" specifies the how many characters the extracted substring will contain.
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlMidServlet 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 passed the query "SELECT MID(" + "'" +str+"'"+","+ind_pos+","+len+")"; (Here 'str', 'ind_pos', 'len' are variables that stores the value given by the user in their respective textfields.) 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 :
mid.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>MID function</title> </head> <body> <form action="MysqlMidServlet" method="get"> <table> <tr> <td>Enter String </td> <td><input type="text" name="text1"/></td> </tr> <tr> <td>Enter index position </td> <td><input type="text" name="text2"/></td> </tr> <tr> <td>Enter length </td> <td><input type="text" name="text3"/></td> </tr> <tr> <td></td> <td><input type="submit" value="submit"/></td> </tr> </table> </form> </body> </html>
MysqlMidServlet.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 MysqlMidServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String str = request.getParameter("text1");
int ind_pos = Integer.parseInt(request.getParameter("text2"));
int len = Integer.parseInt(request.getParameter("text3"));
String className = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://192.168.10.13";
String user = "root";
String password = "root";
Connection con;
PreparedStatement ps, ps1;
ResultSet rs, rs1;
try {
Class.forName(className);
con = DriverManager.getConnection(url, user, password);
String sql = "SELECT MID(" + "'" +str+"'"+","+ind_pos+","+len+")";
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
sql = rs.getString(1);
out.println("Extracted substring = "+ 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>MysqlMidServlet</servlet-name> <servlet-class>MysqlMidServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlMidServlet</servlet-name> <url-pattern>/MysqlMidServlet</url-pattern> </servlet-mapping> </web-app>
Output
When you will execute the above example you will get the output as :
1.
2.
3.
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