SQL exception thrown when the method is called otherwise working fine - mysql

Question

I am making a web application project using JSP in Netbeans IDE.
I have a java Class called Login which has a static method called authenticate.When I am running this file it gives me the required output. Now I have a web page called auth.jsp which calls the method authenticate but when I try to run this web page the value returned by the method is "error" that is sql exception is being thrown by the method. Could someone please tell why this is happening? Thanks in advance.
package server;
import java.sql.*;
public class Login {
public static void main(String args[]) {
System.out.print(authenticate("260","abc"));
}
public static String authenticate(String username, String password) {
String auth="",pass="";
int blocked_status=0;
String url = "jdbc:mysql://localhost:3306/radio";
try{
Connection conn = DriverManager.getConnection(url,"root","rishabh");
Statement stmt = conn.createStatement();
String sql = "select password,blocked from user where username = \"" + username + "\"";
ResultSet rs = stmt.executeQuery(sql);
int flag=0;
while(rs.next()){
pass = rs.getString("password");
blocked_status = rs.getInt("blocked");
flag++;
}
if(flag>0) {
if(blocked_status==1)
auth = "blocked";
else if(pass.equals(password))
auth = "authenticated";
else if(pass.equalsIgnoreCase(pass))
auth = "wrong_case";
else
auth = "wrong_password";
}
else{
auth = "incorrect_username";
}
} catch(SQLException e){
auth = "sqlerror";
System.out.print(" ERROR " );
}
return auth;
}
}