In this tutorial you will learn how to use substr() String function of mysql with java servlet.
Mysql SUBSTR() Function Example Using Java Servlet
In this tutorial you will learn how to use substr() String function of mysql with java servlet.
SUBSTR() function of Mysql gives back a part of an actual string. A specified number of characters that are returned from the actual string is called 'substring'. To retrieve the substring in this function, it is required to specify the position and length of a substring into an actual string because of from where and how many characters you want in a substring.
Syntax :
substr('str', pos, len);
Here "str", is an actual string, "pos" specifies from where you want to retrieve the substring, and "len" specifies the how many characters you want into the substring.
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlSubStrServlet 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 in my java code "SELECT SUBSTR(" + "'" + str + "'"+","+ pos +"," +len+")"; (Here 'str', '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 :
substr.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>SUBSTR FUNCTION</title> </head> <body> <form action="MysqlSubStrServlet" method="get"> <table> <tr> <td>Enter String </td> <td><input type="text" name="text1"/></td> </tr> <tr> <td>Enter the position </td> <td><input type="text" name="text2"/></td> </tr> <tr> <td>Enter the length of a string </td> <td><input type="text" name="text3"/></td> </tr> <tr> <td></td> <td><input type="submit" value="submit"/></td> </tr> </table> </form> </body> </html>
MysqlSubStrServlet.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 MysqlSubStrServlet 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 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;
ResultSet rs;
try {
Class.forName(className);
con = DriverManager.getConnection(url, user, password);
String sql = "SELECT SUBSTR(" + "'" + str + "'"+","+ pos +"," +len+")";
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
sql= rs.getString(1);
out.println("Substring 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>MysqlSubStrServlet</servlet-name> <servlet-class>MysqlSubStrServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlSubStrServlet</servlet-name> <url-pattern>/MysqlSubStrServlet</url-pattern> </servlet-mapping> </web-app>
Output
1. When you will execute the above example you will get the output as :
2.
3.
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