In this tutorial you will learn how to use left() String function of mysql with java servlet
Mysql LEFT() Function Example Using Java Servlet
In this tutorial you will learn how to use left() String function of mysql with java servlet
LEFT() method of mysql takes the two argument, first as a string and the other as a numeric value. This method gives back the certain number of characters from the left side, as specified in the second argument of this function, from the specified string, as specified in the first argument of this function. In some cases such as if you are giving the numeric value greater than the number of characters of a string then this function simply returns the whole string as it is, and if you are giving the numeric value less than the number of characters of a string then it will not be return anything.
Syntax :
left('string', num);
Here the argument "string" is a string from which you want to fetch the number of characters, and num is a number that will specify the number of characters you want to fetch from the left side of string.
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlLeftServlet 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 LEFT(" + "'" + str + "'"+","+num+")"; (Here 'str' and num 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 :
left.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>LEFT function</title> </head> <body> <form action="MysqlLeftServlet" method="get"> <table> <tr> <td>Enter String</td> <td><input type="text" name="text1"/></td> </tr> <tr> <td>Enter a number</td> <td><input type="text" name="text2"/></td> </tr> <tr> <td></td> <td><input type="submit" value="submit"/></td> </tr> </table> </form> </body> </html>
MysqlLeftServlet.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 MysqlLeftServlet 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 num = Integer.parseInt(request.getParameter("text2"));
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 LEFT(" + "'" + str + "'"+","+num+")";
ps = con.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {
sql = rs.getString(1);
out.println("Characters from the left side of string "+str+" =" + "\"" + 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>MysqlLeftServlet</servlet-name> <servlet-class>MysqlLeftServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlLeftServlet</servlet-name> <url-pattern>/MysqlLeftServlet</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. When you will click on submit button you will get the output as :
[ 0 ] Comments