Determining the location of the file

[Roger Fed]

Hello,
In developing my web application i have used a file to register and search data
the is stored beside the class that do the operations of reading and writing
well, when i write the name of the file as a path for it as follow

 File file=new File("Data.txt");

the compiler flag FileNotFoundException why???
thanks...

[Tim Moores]

Web apps have no concept of a "default directory", so you can't use relative paths for files. You either need to use absolute paths, or -for directories inside your web app directory- use ServletContext.getRealPath(...).

Oh, now I see it's about the compiler error - "new File(...)" throws that exception, so you need to handle it properly (using a try/catch block).

[Bear Bibeault]

getRealPath() won't work in all circumstances. It's best to use ServletContext.getResourceAsStream().

[Zandis Murāns]

new File(...) will never throw an exception.

[Roger Fed]

this isn't servlet
it is normal class so the ServletContext will not work here

[Bear Bibeault]

Get the stream at the servlet level and pass it to the normal class.

There's no way that your "normal" class can determine the location of the file (unless the full path is hard-coded -- not a good idea) without the help of the servlet layer.

Or, place the file somewhere in the classpath and use ClassLoader.getResourceAsStream().

Or, store the absolute path of the file in a properties file that you read at run time.

[Roger Fed]

this is the class

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package web;

import java.io.File;
import java.io.IOException;
import java.util.Scanner;
import javax.servlet.ServletContext;

/**
 *
 * @author Moustafa
 */
public class UserIO {
    public static User getUser(String username, String password) throws IOException {        
        File file=new File("Data.txt");
         Scanner input=new Scanner(file);
         boolean isFound=false;
         while (input.hasNext()) {            
            String nameInFile=input.next();
            String passwordInFile=input.next();
            if(nameInFile.equalsIgnoreCase(username) && passwordInFile.equals(password)){
                isFound=true;
                break;
            }
        }
         input.close();
         if(isFound){
             User user=new User();
             user.setUsername(username);
             user.setPassword(password);
             return user;
             
         }
         else
             return null;
        
    }
}

[Bear Bibeault]

If it's a normal class why is it importing servlet classes?

[Bear Bibeault]

And, what's the purpose of reading the file in the first place?

[Roger Fed]

i was trying to use ServletContext

[Bear Bibeault]

Depending on what you are really trying to do the best solution is likely to not be moving servlet information into the class.

But you haven't answered my latest question yet.

[Roger Fed]

this class will search in the file about the username and password specified
and if found it return a User object that will be put in the session later

[Bear Bibeault]

Roger Fed wrote:this class will search in the file about the username and password specified
and if found it return a User object that will be put in the session later

What's in the file that needs to be looked up? Is this not something better handled by a database?

[Roger Fed]

Yes, but i still doesn't have the skills to deal with database

[Bear Bibeault]

In my opinion you are spending a lot of time trying to do things the wrong way, and that time would be better spent learning the skills you lack to do it the right away.

[Pete Nelson]

If you're just using this for a learning experience (your reasoning for not wanting to involve a database), you may want to consider making the username / password either servlet init parameters, or context parameters for the web application. DO NOT DO THIS WITH A SECURE PASSWORD, but if you want to use it just for testing, this might be a good approach.

Bear's right. For an actual enterprise solution, a database (or LDAP server) is a better option.

<!-- web.xml snippet --> <context-param> <param-name>username</param-name> <param-value>testuser</param-value> </context-param> <context-param> <param-name>password</param-name> <param-value>secret</param-value> </context-param>

// servlet code snippet
String username = getServletContext().getInitParameter("username");
String password = getServletContext().getInitParameter("password");

// now compare your user & password against request parameters
// ...