In this tutorial you will learn how to use char() String function of mysql with java servlet
Mysql CHAR() Function Example Using Java Servlet
In this tutorial you will learn how to use char() String function of mysql with java servlet
CHAR() method of mysql, a numeric value is passed into its parameter and then it gives back the corresponding character value as per the ASCII table.
Syntax :
char(num);
Here num is an integer value whose character value you want to retrieve.
Now, since I have to use this function in java servlet program, therefore I have created a java servlet class named MysqlCharServlet 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 an input 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 CHAR("+"'"+chr+"'"+")"; (This query will return a corresponding character value as per ASCII table for the integer value input by the user. In this query chr is a variable name that stores the value that is given by the user. getParameter() method is used to take and store the value of this variable in source/java code.) 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 :
Char.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>Character for the corresponding ASCII code</title> </head> <body> <form method="get" action="MysqlCharServlet"> <table><tr><td>Enter a numeric value <input type="text" name="txtName"/></td></tr> <tr><td align="center"><input type="submit" value="Find CharacterForASCIICode"/> </table> </form> </body> </html>
MysqlCharServlet.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 MysqlCharServlet extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String chr = request.getParameter("txtName");
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 CHAR("+"'"+chr+"'"+")";
ps = con.prepareStatement(sql);
rs=ps.executeQuery();
while(rs.next())
{
sql = rs.getString(1);
out.println("Corresponding Character for "+"\""+chr+"\" = "+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>MysqlCharServlet</servlet-name> <servlet-class>MysqlCharServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>MysqlCharServlet</servlet-name> <url-pattern>/MysqlCharServlet</url-pattern> </servlet-mapping> </web-app>
Output
When you will execute the above example you will get the output as :
1.
2. When enter a numeric value as :
3. Corresponding character will look like as :
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